B
Fig. 6.16 Superior limbic keratoconjunctivitis: A, Diagrammatic depiction; B, Clinical photograph
120	Section III   Diseases of Eye


THYGESON’S SUPERFICIAL PUNCTATE KERATITIS
It is a type of chronic, recurrent bilateral superficial punctate keratitis, which has got a specific clinical identity.
Etiology
Exact etiology is not known.
• A viral origin has been suggested without any conclusion.
• An allergic or dyskeratotic nature also has been suggested owing to its response to steroids.
Clinical features
• Age and sex. It may involve all ages with no sex predilection.
• Laterality. Usually bilateral.
• Course. It is a chronic disease characterised by remissions and exacerbations.
Symptoms
It may be asymptomatic, but is usually associated with foreign body sensation, photophobia and lacrimation.
Signs
• Conjunctiva is uninflamed (no conjunctivitis).
• Corneallesions.There are coarse punctate epithelial lesions (snow flake) circular, oval or stellate in shape, slightly elevated and situated in the central part (pupillary area) of cornea. Each lesion is a cluster of heterogeneous granular grey dots.
Treatment
• Disease is self-limiting with remissions and may permanently disappear in a period of 5–6 years.
• Topical steroids during exacerbations the lesions and associated symptoms usually respond quickly to topical steroids (so, should be tapered rapidly).
• Therapeutic soft contact lenses may be required in steroid-resistant cases.
FILAMENTARY KERATITIS
It is a type of superficial punctate keratitis, associated with formation of corneal epithelial filaments.
Pathogenesis
Corneal filaments which essentially consist of a tag of elongated epithelium are formed due to aberrant epithelial healing. Therefore, any condition that leads to focal epithelial erosions may produce filamentary keratopathy.
Causes
Common conditions associated with filamentary keratopathy are:
1. Keratoconjunctivitis sicca (KCS).
2. Superior limbic keratoconjunctivitis.


3. Epitheliopathy due to radiation keratitis.
4. Following epithelial erosions as in herpes simplex keratitis, Thygeson’s superficial punctate keratitis, recurrent corneal erosion syndrome and trachoma.
5. Prolonged patching of the eye particularly following ocular surgery like cataract.
6. Systemic disorders like diabetes mellitus, ectodermal dysplasia and psoriasis.
7. Idiopathic.

Clinical features
Symptoms
Patients usually experience moderate pain, ocular irritation, lacrimation and foreign body sensation.
Signs
Corneal examination reveals (Fig. 6.15G and H):
• Filaments i.e., fine tags of elongated epithelium which are firmly attached at the base, intertwined with mucus and degenerated cells. The filament is freely movable over the cornea.
• Superficial punctate keratitis of varying degree is usually associated with corneal filaments.
Treatment
1. Managementoffilamentsinclude their mechanical debridement and patching for 24 hours followed by lubricating drops.
2. Therapeutic soft contact lenses may be useful in recurrent cases.
3. Treatment of the underlying cause to prevent recurrence.

DEEP KERATITIS

An inflammation of corneal stroma with or without involvement of posterior corneal layers constitutes deep keratitis, which may be non-suppurative or suppurative.
■Non-suppurativedeepkeratitisincludes, interstitial keratitis, disciform keratitis, keratitis profunda and sclerosing keratitis. ■Suppurativedeepkeratitisincludes central corneal abscess and posterior corneal abscess, which are usually metastatic in nature.
INTERSTITIAL KERATITIS
Interstitial keratitis denotes an inflammation of the corneal stroma without primary involvement of the epithelium or endothelium.
Causes. Its common causes are: • Congenital syphilis
• Tuberculosis
• Cogan’s syndrome
Chapter 6	Diseases of Cornea	121


• Acquired syphilis • Trypanosomiasis • Malaria
• Leprosy
• Sarcoidosis.

Syphilitic (Luetic) Interstitial Keratitis Syphilitic interstitial keratitis is associated more frequently (90%) with congenital syphilis than the acquired syphilis. The disease is generally bilateral in inherited syphilis and unilateral in acquired syphilis. In congenital syphilis, manifestations develop between 5–15 years of age.
Pathogenesis
It is now generally accepted that the disease is a manifestation of local antigen-antibody reaction. It is presumed that Treponema pallidum invades the cornea and sensitizes it during the period of its general diffusion throughout the body in the foetal stage. Later a small scale fresh invasion by Treponema or toxins excite the inflammation in the sensitized cornea. The inflammation is usually triggered by an injury or an operation on the eye.
Clinical features
Interstitial keratitis characteristically forms one of the late manifestations of congenital syphilis. Many times it may be a part of Hutchinson’s triad, which includes interstitial keratitis, Hutchinson’s teeth and vestibular deafness.
The clinical features of interstitial keratitis can be divided into three stages: initial progressive stage, florid stage and stage of regression.
1. Initial progressive stage. The disease begins with oedema of the endothelium and deeper stroma, secondary to anterior uveitis, as evidenced by the presence of keratic precipitates (KPs). There is associated pain, lacrimation, photophobia, blepharospasm and circumcorneal injection followed by a diffuse corneal haze giving it a ground glassappearance.This stage lasts for about 2 weeks. 2. Florid stage. In this stage, eye remains acutely inflamed. Deep vascularization of cornea, consisting of radial bundle of brush-like vessels develops. Since, these vessels are covered by hazy cornea, they look dull reddish pink which is called ‘Salmon patch appearance’ (Fig. 6.17). There is often a moderate degree of superficial vascularization. These vessels arising from the terminal arches of conjunctival vessels, run a short distance over the cornea. These vessels and conjunctiva heap at the limbus in the form of epulit. This stage lasts for about 2 months.














Fig. 6.17 Intenstitial keratitis: Salmon patch appearance

3.Stage of regression. The acute inflammation resolves with the progressive appearance of vascular invasion. Clearing of cornea is slow and begins from periphery and advances centrally. Resolution of the lesion leaves behind some opacities and ghostvessels.This stage may last for about 1 to 2 years.
Diagnosis
The diagnosis is usually evident from the clinical profile. A positive VDRL or Treponema pallidum immobilization test confirms the diagnosis.
Treatment
The treatment should include topical treatment for keratitis and systemic treatment for syphilis.
1. Local treatment includes:
• Topical corticosteroid drops e.g., dexamethasone 0.1% drops every 2–3 hours. As the condition is allergic in origin, corneal clearing occurs with steroids if started well in time and a useful vision is obtained.
• Atropine eye ointment 1% 2–3 times a day. • Dark goggles to be used for photophobia.
• Keratoplasty is required in cases where dense corneal opacities are left.
2. Systemic treatment includes:
• Penicillin in high doses should be started to prevent development of further syphilitic lesions. However, an early treatment of congenital syphilis usually does not prevent the onset of keratitis at a later stage.
• Systemicsteroidsmay be added in refractory cases of keratitis.

Tuberculous Interstitial Keratitis
The features of tubercular interstitial keratitis are similar to syphilitic interstitial keratitis except that it is more frequently unilateral and sectorial (usually involving a lower sector of cornea).
122	Section III   Diseases of Eye


Treatment consists of systemic antitubercular drugs, topical steroids and cycloplegics.

Cogan’s Syndrome
This syndrome comprises the interstitial keratitis of unkown etiology, acute tinnitus, vertigo, and deafness. It typically occurs in middle-aged adults and is often bilateral.
Treatment consists of topical and systemic cortico-steroids. An early treatment usually prevents permanent deafness and blindness.

CORNEAL DEGENERATIONS

Corneal degenerations refers to the conditions in which the normal cells undergo some degenerative changes under the influence of age or some pathological condition.
Classification
A. Depending upon location
I. Axial corneal degenerations 1. Fatty degeneration
2. Hyaline degeneration 3. Amyloidosis
4. Calcific degeneration (Band keratopathy) 5. Salzmann’s nodular degeneration.
II. Peripheral degenerations 1. Arcus senilis
2. Vogt’s white limbal girdle 3. Hassall-Henle bodies
4. Terrien’s marginal degeneration 5. Mooren’s ulcer
6. Pellucid marginal degeneration
7. Furrow degeneration (senile marginal degen-eration).
B. Depending upon etiology
I.  Age-related degenerations. Arcus senilis, Vogt’s white limbal girdle, Hassall-Henle bodies, Mosaic degeneration.
II. Pathological degenerations. Fatty degeneration, amyloidosis, calcific degeneration, Salzmann’s nodular degeneration, Furrow degeneration, spheroidal degeneration, Pellucid marginal degeneration, Terrien’s marginal degeneration, Mooren’s ulcer.
I. AGE-RELATED CORNEAL DEGENERATIONS
Arcus Senilis
Arcus senilis refers to an annular lipid infiltration of corneal periphery. This is an age-related change occurring bilaterally in 60% of persons between 40 and 60 years of age and in nearly all individuals over

the age of 80. Sometimes, similar changes may occur in young persons (arcusjuvenilis)which may or may not be associated with hyperlipidemia.

Clinical features
• The arcus starts in the superior and inferior quadrants and then progresses circumferentially to form a ring which is about 1 mm wide. Peripheral border of this ring opacity is sharp while central border is diffuse.
• This ring of opacity is separated from the limbus by a clear zone (the lucid interval of Vogt) (Fig. 6.18).
• Sometimes there may be double ring of arcus.

Vogt’s White Limbal Girdle
It is also an age-related change seen frequently in elderly people. It appears as bilateral chalky white opacities in the interpalpebral area both nasally and temporally. There may or may not be a clear area between opacity and the limbus. The opacity is at the level of Bowman’s membrane.

Hassall-Henle Bodies
Hassall-Henle bodies are drop-like excrescences of hyaline material projecting into the anterior chamber around the corneal periphery. These arise from Descemet’s membrane. These form the commonest senile change seen in the cornea. In pathological conditions, they become larger and invade the central area and the condition is called cornea guttata.

II. PATHOLOGICAL CORNEAL DEGENERATIONS Fatty Degeneration (Lipoid Keratopathy) Fatty degeneration of cornea is characterised by whitish or yellowish deposits. The fat deposits mostly consist of cholesterol and fatty acids. Initially fat deposits are intracellular but some become extracellular with necrosis of stromal cells. Lipid keratopathy can be primary or secondary.















Fig. 6.18 Arcus senilis
Chapter 6	Diseases of Cornea	123


1. Primary lipid keratopathy is a rare condition which occurs in a cornea free of vascularization. Serum lipid levels are normal in such patients.
2. Secondarylipidkeratopathyoccurs in vascularised cornea secondary to diseases such as corneal infections, interstitial keratitis, ocular trauma, glaucoma, and chronic iridocyclitis.
Treatment is usually unsatisfactory. In some cases slow resorption of lipid infiltrate can be induced by argon laser photocoagulation of the new blood vessels.

Hyaline Degeneration
Hyaline degeneration of cornea is characterised by deposition of hyaline spherules in the superficial stroma and can be primary or secondary.
1. Primary hyaline degeneration is bilateral and noted in association with granular dystrophy.
2. Secondary hyaline degeneration is unilateral and associated with various types of corneal diseases including old keratitis, long-standing glaucoma, trachomatous pannus. It may be complicated by recurrent corneal erosions.
Treatment of the condition when it causes visual disturbance is keratoplasty.

Amyloid Degeneration
Amyloid degeneration of cornea is characterised by deposition of amyloid material underneath its epithelium. It is very rare condition and occurs in primary (in a healthy cornea) and secondary forms (in a diseased cornea).

Calcific Degeneration (Band Shape Keratopathy)
Band shape keratopathy (BSK) is essentially a degenerative change associated with deposition of calcium salts in Bowman’s membrane, most superficial part of stroma and in deeper layers of epithelium.
Etiology
• Oculardiseasescomplicated by band keratopathy include chronic uveitis in adults, children with Still’s disease, phthisis bulbi, chronic glaucoma, chronic keratitis and ocular trauma.
• Age-relatedBSK is common and affects otherwise healthy cornea.
• Primary BSK is familial.
• Metabolic conditions rarely associated with BSK include hypercalcaemia, hyperphosphataemia, hyperuricemia and chronic renal failure.
Clinical features
It typically presents as a band-shaped opacity in the interpalpebral zone with a clear interval between the ends of the band and the limbus (Fig. 6.19). The














Fig. 6.19 Band-shaped keratopathy in a patient with chronic uveitis

condition begins at the periphery and gradually progresses towards the centre. The opacity is beneath the epithelium which usually remains intact. Surface of this opaque band is stippled due to holes in the calcium plaques in the area of nerve canals of Bowman’s membrane. In later stages, transparent clefts due to cracks or tears in the calcium plaques may also be seen.
Treatment
1. Chelation, i.e., chemical removal of deposited calcium salts is an effective treatment. First of all, corneal epithelium is scraped under local anaesthesia. Then 0.01 molar solution of EDTA (chelating agent) is applied to the denuded cornea with the help of a cotton swab for about 10 minutes. This removes most of the deposited calcium. Pad and bandage is then applied for 2–3 days to allow the epithelium to regenerate.
2. Phototherapeutickeratectomy(PTK) with excimer laser is very effective in clearing the cornea.
3. Keratoplasty may be performed when the band keratopathy is obscuring useful vision.
4. Treatment of underlying causative disease.

Salzmann’s Nodular Degeneration
Etiology. This condition occurs in eyes with recurrent attacks of phlyctenular keratitis, rosacea keratitis and trachoma. The condition occurs more commonly in women and is usually unilateral.
Pathogenesis. In Salzmann’s nodular degeneration, raised hyaline plaques are deposited between epithelium and Bowman’s membrane. There is associated destruction of Bowman’s membrane and the adjacent stroma.
Clinical features. Clinically, one to ten bluish white elevations (nodules), arranged in a circular fashion,
124	Section III   Diseases of Eye
















Fig. 6.20 Salzmann’s nodular degeneration

are seen within the cornea (Fig. 6.20). Patient may experience discomfort due to loss of epithelium from the surface of nodules. Visual loss occurs when nodules impinge on the central zone.
Treatment is essentially by keratoplasty.
Furrow Degeneration (Senile Marginal Degeneration)
In this condition, thinning occurs at the periphery of cornea leading to formation of a furrow. In the presence of arcus senilis, the furrow occupies the area of lucid interval of Vogt. Thinning occurs due to fibrillar degeneration of the stroma.
Patient develops defective vision due to induced astigmatism.
Treatment is usually not necessary.
Spheroid Degeneration
(Climatic droplet keratopathy/Labrador keratopathy/ Bietti’s nodular dystrophy)/corneal elastosis). Etiology.It typically occurs in men who work outdoors, especially in hostile climates. Its occurrence has been related to exposure to ultraviolet rays and/ or ageing and/or corneal disease.
Clinical features. In this condition, amber-coloured spheroidal granules (small droplets) accumulate at the level of Bowman’s membrane and anterior stroma in the interpalpebral zone (Fig. 6.21). In marked degeneration, the vision is affected. Treatment in advanced cases is by corneal trans-plantation.
Pellucid Marginal Degeneration
It is characterised by corneal thinning involving the periphery of lower cornea. It induces marked astigmatism which is corrected by scleral type contact lenses.
Terrien’s Marginal Degeneration
Terrien’s marginal degeneration is non-ulcerative thinning of the marginal cornea.


Fig. 6.21 Spheroid corneal degeneration

Clinical features are as follows:
1. Predominantly affects males usually after 40 years of age.
2. Mostly involves superior peripheral cornea.
3. Initial lesion is asymptomatic corneal opacification separated from limbus by a clear zone.
4. The lesion progresses very slowly over many years with thinning and superficial vascularization. Dense yellowish white deposits may be seen at the sharp leading edge (Fig. 6.22). Patient experiences irritation and defective vision (due to astigmatism). Complications such as perforation (due to mild
trauma) and pseudopterygia may develop. Treatment isnon-specific. In severe thinning, a patch of corneal graft may be required.

CORNEAL DYSTROPHIES

Corneal dystrophies are inherited disorders in which the cells have some inborn defects due to which pathological changes may occur with passage of time leading to development of corneal haze in otherwise normal eyes that are free from inflammation or















Fig. 6.22 Terrien’s marginal degeneration
Chapter 6	Diseases of Cornea	125


vascularization. There is no associated systemic disease. Dystrophies occur bilaterally, manifesting occasionally at birth, but more usually during first or second decade and sometimes even later in life.
Note. Recent studies have revealed that all the above definitions are not true for every type of corneal dystrophy. However, the International Committee for Classification of Corneal Dystrophies (2008) has decided to continue with the above given customary definition of corneal dystrophies.
Classification
The International Committee for Classification of Corneal Dystrophies (IC3D) in 2008 has proposed a new classification of corneal dystrophies, which in addition to the anatomic basis (site primarily involved) also incorporates the current clinical, pathological and genetic basis. Therefore, dystrophies with a common genetic basis, i.e., TGFB1 dystrophies have been grouped together (irrespective of the primary location of the lesion). The new IC3D classification of corneal dystrophies is as below:
I.  Epithelial and subepithelial dystrophies
1. Epithelial basement membrane dystrophy (EBMD).
2. Epithelial recurrent erosion dystrophy (ERED). 3. Subepithelial mucinous corneal dystrophy
(SMCD).
4. Mutation in keratin genes: Meesmann corneal dystrophy (MECD).
5. Lisch epithelial corneal dystrophy (LECD).
6. Gelatinous drop-like corneal dystrophy (GDLD).
II. Bowman layer dystrophies
1. Reis-Bucklers corneal dystrophy (RBCD) Granular corneal dystrophy type 3.
2. Thie-Behnke corneal dystrophy (TBCD).
3. Grayson-Wilbrandt corneal dystrophy (GWCD). III. Stromal dystrophies
1. TGFb1 corneal dystrophies a. Lattice corneal dystrophy
i.  Classic lattice corneal dystrophy 1 (LCD 1) ii. Lattice corneal dystrophy, gelsolin type 2
(LCD 2)
b. Granular corneal dystrophy
i.  Granular corneal dystrophy, type 1 (classic) (GCD 1)
ii. Granular corneal dystrophy, type 2 (granular lattice) (GCD 2)
iii.Granular corneal dystrophy, type 3 (GCD 3) 2. Macular corneal dystrophy (MCD).
3. Schnyder corneal dystrophy (SCD).
4. Congenital stromal corneal dystrophy (CSCD).

5. Fleck corneal dystrophy (FCD).
6. Posterior amorphous corneal dystrophy (PACD).
7. Central cloudy dystrophy of Francois (CCDF). 8. Pre-Descemet corneal dystrophy (PDCD).
IV.Descemet membrane and endothelial dystrophies 1. Fuchs endothelial corneal dystrophy (FECD). 2. Posterior polymorphous corneal dystrophy
(PPCD).
3. Congenital hereditary endothelial dystrophy 1 (CHED 1).
4. Congenital hereditary endothelial dystrophy 2 (CHED 2).
5. X-linked endothelial corneal dystrophy (XECD).

I. EPITHELIAL AND SUBEPITHELIAL DYSTROPHIES

1. Epithelial Basement Membrane Dystrophy Epithelial basement membrane dystrophy (EBMD) is also known as map-dot-fingerprint dystrophy or Cogan microcystic epithelial dystrophy or anterior basement membrane dystrophy.
Inheritance. Most cases have no inheritance documented.
Genetic locus and gene  are 5q31 and TGFb1, respectively.
Onset, course and symptoms. Presents in adult life, rarely seen in children. Asymptomatic or recurrent erosions with pain, lacrimation and blurred vision are observed. Except for the bleb pattern, on-axis lesions may also cause blurred vision due to irregular astigmatism. Location and degree of pathology can fluctuate with time.
Signs. Typical lesions include (Fig. 6.23):
•  Maps. Irregular islands of thickened, gray, hazy epithelium with scalloped, circumscribed borders,














Fig. 6.23 Epithelial basement membrane dystrophy
126	Section III   Diseases of Eye


particularly affecting the central or paracentral cornea. Isolated or combined with other signs.
•  Dots (Cogan). Irregular round, oval or comma-shaped, non-staining, putty-gray opacities. Clustered like an archipelago in the central cornea. Typically combined with other signs, especially with maps.
•  Fingerprint lines. Parallel, curvilinear lines, usually paracentral, best seen in retroillumination. They may be isolated or combined with other signs, especially maps.
•  Bleb pattern (Bron). A subepithelial pattern like pebbled glass, best seen by retroillumination. Isolated or combined with other signs.
Note. Poor adhesion of basal epithelial cells to abnormal basal laminar material is thought predisposition to recurrent erosions.
2. Epithelial Recurrent Erosion Dystrophy Onset and course. Epithelial recurrent erosion dystrophy (ERED), also known as corneal erosions or recurring hereditary dystrophy, usually occurs in first decade of life.
Inheritance is autosomal dominant.
Genetic locus and gene involved are unknown.
Onset and course. Recurrent corneal erosions appear typically at 4–6 years of age but occasionally as early as 8 months of age. Attacks generally decline in frequency in intensity and cease by the age of 50 years. Signs include (Fig. 6.24):
• Corneal erosions are seen during the attack recurrent corneal erosions appear typically at 4–6 years of age but occasionally as early as 8 months of age. Attacks generally decline in frequency and intensity and cease by the age of 50 years.
• Subepithelial haze or blebs may be seen between the attacks.














Fig. 6.24 Lattice corneal dystrophy


• Central subepithelial corneal opacities, may appear as early as 7 years of age. These vary from subepithelial fibrosis to protruding keloid-like nodules.
Symptoms are precipitated by minimal trauma or occur spontaneously and are in the form of attacks of redness, photophobia, epiphora and ocular pain. Treatment. About 25% of the patients may eventually need corneal grafts at the mean age of 45 years.

3. Subepithelial Mucinous Corneal Dystrophy
Inheritance is autosomal dominant. Genetic locus and gene is unknown.
Onset and course. Onset is in the first decade of life and progressive loss of vision occurs in adole-scence.
Signs include bilateral subepithelial opacities and haze, most dense centrally, involving the entire cornea. Symptoms include painful episodes of recurrent corneal erosions, which decrease during adolescence.
4. Mutations in Keratin Genes: Meesmann Corneal Dystrophy
Onset and course. Meesmann corneal dystrophy (MECD) also known as juvenile hereditary epithelial dystrophy occurs in early childhood and the condition is slowly progressive. Its variant is Stocker-Holt dystrophy.
Inheritance is autosomal dominant.
Genetic loci are 12q13 (KRT3) and 17q12 (KRT 12) for Stocker-Holt variant .
Genes involved are Keratin K3 (KRT3) and Keratin K12 (KRT12) for Stocker-Holt variant.
Signs. Characteristic lesions include:
• Multiple,tinyepithelialvesicleswhich extend to the limbus and are most numerous in the interpalpebral area with clear surrounding epithelium.
• Whorled and wedge-shaped epithelial patterns have also been reported.
• Corneal thinning and reduction in corneal sensation may be noted.
• In Stocker-Holt variant, the entire cornea demonstrates fine, grayish punctate epithelial opacities that stain with fluorescein and fine linear opacities that may appear in a whorl pattern.
Symptoms. Patients are typically asymptomatic or may have mild visual reduction, although some patients complain of glare and light sensitivity. Recurrent painful punctiform epithelial erosions may occur. Rarely, blurred vision results from corneal irregularity and scarring.
Chapter 6	Diseases of Cornea	127


5. Lisch Epithelial Corneal Dystrophy
Onset and course. Lisch epithelial corneal dystrophy (LECD) also known as band-shaped and whorled microcystic dystrophy of the corneal epithelium occurs in childhood and there occurs slow progression of opacities with possible deterioration in vision. Inheritance is X-chromosomal dominant.
Signs are as below.
• Direct illumination shows localized gray opacities in different patterns: whorl-like, radial, band-shaped, flame/feathery shaped, and club shaped.
• Indirect illumination demonstrates multiple, densely crowded clear cysts with clear surrounding epithelium.
Symptoms. The condition is asymptomatic, blurring of vision occurs if the pupillary zone is involved.
6. Gelatinous Drop-Like Corneal Dystrophy (GDLD)
Onset and course. Gelatinous drop-like corneal dystrophy (GDLD) also known as subepithelial amyloidosis or primary familial amyloidosis (Grayson) occurs in the first decade of life and the condition is progressive.
Genetic locus is 1p32 and gene involved is tumour-associated calcium signal transducer 2 (TACSTD2) Inheritance is autosomal recessive.
Signs include:
• Subepithelial lesions which appear initially may be similar to band-shaped keratopathy or there may be groups of small multiple nodules, that is, mulberry configuration.
• Superficial vascularization is frequently seen.
• Stromalopacificationor larger nodular lesions, that is, kumquat-like lesions may appear in later life. Symptoms include significant decrease in vision,
photophobia, irritation, redness, and tearing.

II. BOWMAN LAYER DYSTROPHIES
1. Reis-Bucklers Corneal Dystrophy
Onset and course. Reis-Bucklers corneal dystrophy (RBCD) also known as corneal dystrophy of Bowman layer, type I (CDB I) or geographic corneal dystrophy (Weidle), occurs in childhood and causes slowly progressive deterioration of vision.
Genetic locus is 5q31 and the gene involved is TGFBI. Inheritance is autosomal dominant.
Signs include confluent irregular and coarse geographic-like opacities with varying densities


which develop at the level of Bowman layer and superficial stroma, initially separated from one another. Opacities may extend to the limbus and deeper stroma with time.
Symptoms. Vision is impaired from childhood. Recurrent corneal erosions cause ocular discomfort and pain in the first decade but may become less severe from the end of the second decade.
2. Thiel-Behnke Corneal Dystrophy
Onset and course. Thiel-Behnke corneal dystrophy (TBCD) also known as corneal dystrophy of Bowman layer, type II (CDB2) or honeycomb-shaped corneal dystrophy occurs in childhood and causes slowly progressive deterioration of vision.
Genetic locus is 5q31 and the gene involved is TGFB1. Inheritance is autosomal dominant.
Onset and course. Occurs in childhood and there occurs slowly progressive deterioration of vision from increasing corneal opacification.
Signs include symmetrical subepithelial reticular (honeycomb) opacities with peripheral cornea typically uninvolved, which can progress to deep stromal layers and corneal periphery.
Symptoms. Recurrent corneal erosions cause ocular discomfort and pain in the first and second decade. Gradual visual impairment develops later.
3. Grayson-Wilbrandt Corneal Dystrophy (GWCD)
Onset and Course. Occurs during first to second decade of life and the condition is progressive. Inheritance is autosomal dominant.
Signs. Bowman layer demonstrates variable patterns of opacification from diffuse mottling to diffuse gray-white opacities, which extend anteriorly into the epithelium. The cornea between the deposits is clear. Refractile bodies are described in corneal stroma.
Symptoms. Decreased to normal visual acuity. Recurrent corneal erosions may cause ocular discomfort and pain.
III. STROMAL CORNEAL DYSTROPHIES
1. TGFB1 Corneal Dystrophies These include:
A. Lattice corneal dystrophy, which is of two types: i.  Classic lattice corneal dystrophy (LCD1)
ii. Lattice corneal dystrophy, gelsolin type (LCD2) B. Granularcornealdystrophy, which is of three types: i.  Granular corneal dystrophy, type 1 (classic)
(GCD1)
128	Section III   Diseases of Eye


ii. Granular corneal dystrophy, type 2 (granular lattice) (GCD2)
iii.Granular corneal dystrophy, type 3 (GCD3).

A. Lattice corneal dystrophy
i.  Classical lattice corneal dystrophy:
Classic lattice corneal dystrophy (LCD1) is also known as Biber-Haab-Dimmer dystrophy.
Genetic locus is 5q31 and the gene involved is TGFB1. Inheritance is autosomal dominant.
Onset, symptoms and course. It appears at the age of 2 years and the condition is progressive. Recurrent erosions are frequent and ocular discomfort and pain occurs sometimes starting as early as in the first decade of life. Progressive clouding of central cornea is apparent by the age of 20 years. Soon, visual acuity is impaired. Usually penetrating keratoplasty is required by the age of 30–40 years.
Signs. The disease is characterised by branching spider-like amyloid deposits forming an irregular lattice work in the corneal stroma, sparing the periphery (Fig. 6.24). The number of lattice lines may differ between the 2 eyes and the dystrophy may be difficult to diagnose in some younger patients.
ii.  Lattice corneal dystrophy, Gelsolin Type (LCD2) Lattice corneal dystrophy, Gelsolin type is also known as Familial amyloidosis of Finnish (FAF) or Meretoja syndrome.
Genetic locus is 9q34 and the geneinvolved is Gelsolin GSN.
Inheritance is autosomal dominant.
Onset and course. Onset occurs in third to fourth decade of life, the condition is slowly progressive and the majority of patients are in good health even in the seventh decade.
Signs include:
• Lattice lines appear in the corneal stroma (spreading centripetally from the limbus) which are more peripheral and less numerous than those of lattice dystrophy, type 1. The central cornea is relatively spared.
• Corneal sensitivity is reduced or absent.
Symptoms include:
• Dry eye symptoms are frequent, and corneal erosions may occur late in life.
• Visual acuity is usually normal until the sixth decade because the dystrophy progresses from the peripheral to central cornea.
B. Granular dystrophy
i. Granular corneal dystrophy, Type 1 (Classic) (GCDl) Onset and course. Granular corneal dystrophy, Type 1 (Classic) (GCD 1), also known Corneal dystrophy

Groenouw type 1 occurs in childhood, may be seen as early as 2 years of age. As the condition progresses, the opacities become more confiuent in the superficial cornea.
Genetic locus is5q31 and thegene involved is TGFB1. Inheritance is autosomal dominant.
Signs. The condition is characterised by (Fig. 6.25) milky granular hyaline deposits in anterior stroma. Intervening stroma is clear. Opacities do not extend to the limbus. In children, there may be a vortex pattern of brownish granules superficial to Bowman layer. In later life, granules may extend into the deeper stroma down to Descemet membrane. Symptoms include:
• Glare and photophobia are early symptoms.
• Recurrenterosionsoccur frequently causing ocular discomfort, pain and watering.
• Visualacuitydecreases as opacification progresses with age.
ii.  Granular corneal dystrophy, Type 2 (Granular-
Lattice) (GCD2)
Onset and course. Granular corneal dystrophy, Type 2 (Granular-Lattice) (GCD2) also known as combined granular-lattice corneal dystrophy or Avellino corneal dystrophy, occurs in first decade, may be as early as 3 years of age and the condition is generally progressive. Genetic locus is 5q31 and gene involved is TGFB1. Inheritance is autosomal dominant.
Signs include:
• Subtle superficial stromal tiny whitish dots are initial lesions.
• Ringsorstellate-shapedsnowflakestromalopacities appearing between the superficial stroma and the mid stroma are next lesions.
• Latticelinesin deeper cornea may be seen in some patients. Typically, these lines are located deeper than the snowflake stromal opacity.













Fig. 6.25 Granular corneal dystrophy type 1
Chapter 6	Diseases of Cornea	129


• Superficial, translucent flattened breadcrumb opacities are seen in the final stages, which may coalesce in the anterior stroma.
Symptoms include:
• Visiondecreases with age as the central visual axis becomes affected.
• Pain and ocular discomfort may accompany mild corneal erosions.

2. Macular Corneal Dystrophy
Onset and course. Macular corneal dystrophy (MCD), also known as Groenouw corneal dystrophy type II or Fehr spotted dystrophy, occurs in childhood and is slowly progressive.
Genetic locus is 16q22 and gene involved is carbohydrate sulfotransferase 6 gene—CHST6. Inheritance is autosomal recessive.
Signs include:
• Diffusestromalhazeextending to the limbus is the initial lesion.
• Macules,i.e., superficial, central, elevated, irregular whitish opacities develop later and give the condition its name (Fig. 6.26).
• Posterior peripheral white lesions are also seen. • Corneal sensitivity is reduced.
Symptoms include:
• Recurrent corneal erosions cause photophobia and pain.
• Visualimpairment,usually severe, occurs between 10 and 30 years of age.

3. Schnyder Corneal Dystrophy
Schnyder corneal dystrophy (SCD) is also known as hereditary crystalline stromal dystrophy of Schnyder. Affected patients and non-affected members of the pedigrees may have hyperlipoproteinemia. Genetic locus is 1 p36 and the gene involved is UbiA prenyltransferase domain containing 1—UBIAD1.













Fig. 6.26 Macular corneal dystrophy

Inheritance is autosomal dominant.
Onset and course. The dystrophy appears in early infancy or at birth or sometimes in the first decade of life. It is slowly progressive and usually asymptomatic. Signs include:
• Round ring-shaped central corneal stromal opacities due to deposition of fine needle-like cholesterol crystals, which may be white to yellow or polychromatic in colour are characteristic lesions.
• Corneal sensations decrease with age.
Symptoms include:
• Visual acuity progressively decreases with age. Although scotopic vision may be remarkably good, photopic vision may be disproportionately decreased.
• Glare which increase with age.
4. Congenital Stromal Corneal Dystrophy Onset and course. Congenital stromal corneal dystrophy (CSCD), also known as congenital hereditary stromal dystrophy occurs congenitally and is a nonprogressive or slowly progressive condition. Genetic locus is 12q2l.33 and the gene involved is decorin—DCN.
Inheritance is autosomal dominant.
Signs and symptoms. The characteristic lesions are diffuse, bilateral, corneal clouding with flake-like, whitish stromal opacities throughout the stroma, causing moderate to severe visual loss.
5. Fleck Corneal Dystrophy
Onset and course. Fleck corneal dystrophy (FCD) also known as Francois-Neetens speckled corneal dystrophy occurs congenitally and is a non-progressive condition.
Gene locus is 2q35 and the gene involved is phosphatidylinositol-3-phosphate/phospha-tidylinositol 5-Kinase type III—PIP5K3.
Inheritance is autosomal dominant.
Signs and symptoms. The condition is asymptomatic characterized by small, translucent, discoid opacities or discrete, flat, gray-white, dandruff-like (sometimes ring-shaped) opacities scattered sparsely throughout any level of the otherwise clear stroma.
6. Posterior Amorphous Corneal Dystrophy Onset and course. Posterior amorphous corneal dystrophy (PACD), also known as Posterior amorphous stromal dystrophy, often occurs in the first decade of life. It has been noted as early as 16 weeks, suggesting a congenital nature. The condition is non or slowly progressive.
130	Section III   Diseases of Eye


Inheritance is autosomal dominant.
Signs and symptoms. It presents as diffuse gray-white, sheet-like opacities that can involve any layer of the stroma but are most prominent posteriorly. The condition is largely asymptomatic except for mild decrease in visual acuity (usually better than 6/12).
7. Central Cloudy Dystrophy of Francois Onset and course. Central cloudy dystrophy of Francois (CCDF) occurs in first decade and is non-progressive.
Inheritance is unknown.
Signs and symptoms. The condition is mostly asymptomatic and is characterized by cloudy central polygonal or rounded stromal opacities that fade anteriorly and peripherally and are surrounded by clear tissue.
8. Pre-Descemet Corneal Dystrophy
Onset and course. Onset usually occurs after 30 years of age but has been found in children as young as 3 years. The condition is usually non-progressive, some conditions may show progression. Inheritance is unknown.
Signs and symptoms. The condition is usually asymptomatic and is characterized by focal, fine, gray opacities in the deep stroma immediately anterior to Descemet membrane with a variety of shapes.
IV. DESCEMET MEMBRANE AND ENDOTHELIAL CORNEAL DYSTROPHIES

1.  Fuchs Endothelial Corneal Dystrophy Onset and course. Fuchs endothelial corneal dystrophy (FECD), also known as endoepithelial corneal dystrophy, is frequently seen as a slowly progressive bilateral condition affecting females more than males (F:M::4:1), usually between fifth and seventh decade of life. Primary open angle glaucoma is its common association.
Inheritance. It may be autosomal dominant or sporadic (more common) in nature.
Genetic locus is 13p. No gene has been associated. Clinical features can be divided into following four stages:
1. Stage of cornea guttata. It is characterised by the presence of Hassall-Henle type of excrescenses in the central part of cornea. A gradual increase of central guttae with peripheral spread and confluence gives rise to the so called ‘beaten-metal’appearance. This stage is asymptomatic.
2.  Oedematous  stage  or  stage  of  endothelial decompensation (Fig. 6.27) is characterised by the














Fig. 6.27 Fuch’s endothelial corneal dystrophy

occurrence of early stromal oedema and epithelial dystrophy. Patients complaint of blurring vision.
3. Stageofbullouskeratopathy.This stage follows long-standing stromal oedema and is characterised by marked epithelial oedema with formation of bullae, when rupture cause pain, discomfort and irritation with associated decreased visual acuity.
4. Stage of scarring. In this stage, epithelial bullae are replaced by scar tissue and cornea becomes opaque and vascularized. The condition may sometimes be complicated by occurrence of secondary infection or glaucoma.
Specular microscopy reveals decreased endothelial cell count, increased average cell diameter, decreased hexagons and increased variation in cell size.
Treatment is as follows:
1. Hypertonic saline: (5% sodium chloride) may be of some use in early oedematous stage.
2. Warmairblown on the eyes (e.g. hair dryer) helps in reducing oedema.
3. Intraocular pressure lowering drugs e.g. 0.5% timolol or others should be used to treat associated ocular hypertension.
4. Bandagesoftcontactlensesprovide some relief from disturbing symptoms in bullous keratopathy stage.
5. Penetratingkeratoplastyis the treatment of choice when the visual acuity is reduced markedly.
2.  Posterior Polymorphous Corneal Dystrophy (PPCD)
Onset and course. Posterior polymorphous corneal dystrophy (PPCD) also known as Schlichting dystrophy occurs in early childhood and is very slowly progressive.
Inheritance is autosomal dominant.
Genetic Loci are PPCD 1—20p 1–1.2q 1–1.2; PPCD 2— 1 p34.3—p32.3; PPCD 3—10p 1–1.2.
Chapter 6	Diseases of Cornea	131


Genes involved are: PPCD 1—unknown; PPCD 2— collagen type VIII alpha 2, COL8A2 and PPCD 3— two- handed zinc-finger homeodomain transcription factor 8—ZEB 1.
Signs and symptoms.  The condition is often asymptomatic. The signs include:
• Deep corneal lesions of various shapes including nodular, vesicular (isolated, in clusters, or confluent) and blister-like lesions.
• Railroad tracks appearance lesions (multiple and isolated) (Fig. 6.28).
• Varying gray tissue at the level of Descemet membrane.

3. Congenital Hereditary Endothelial Dystrophy 1
Onset and course. Congenital hereditary endothelial dystrophy 1 (CHED 1 ) occurs in first or second year of life, occasionally congenital. Progression of corneal clouding occurs over 1–10 years.
Genetic Locus is 20p 1 1.2 q 1–1.2 (pericentromeric region) and gene is unknown.
Inheritance is autosomal dominant. Signs and symptoms include:
• Endothelial changes in form of moon crater-like appearance and peau d’orange texture may be seen (Such patients are asymptomatic).
• Corneal clouding ranging from a diffuse haze to a ground-glass, milky appearance with occasional focal gray spots causing blurred vision associated with photophobia and watering. Vision is characteristically worse in the morning.
• Thickening of the cornea, can be 2–3 times of normal thickness.
• Subepithelial band keratopathy may be seen occasionally.
• IOP may be elevated rarely.














Fig. 6.28 Posterior polymorphous corneal dystrophy

4. Congenital Hereditary Endothelial Dystrophy 2
Onset and course. Congenital hereditary endothelial dystrophy 2 (CHED2) also called as Maumenee corneal dystrophy occurs congenitally and is a relatively stationary condition.
Genetic locus is 20p 13 (telomeric portion) and the gene involved is solute carrier family 4, sodium borate transporter, member 11—SLC4A 11. Inheritance is autosomal recessive.
Signs and symptoms are similar to CHED 1 except:
• The condition is more common and severe than CHED 1.
• Nystagmus is often associated.

5. X-linked Endothelial Corneal Dystrophy Onset and course. X-linked endothelial corneal dystrophy (XECD) occurs congenitally and is a progressive condition in males and non-progressive in females.
Genetic locus is Xq25 and the gene involved is unknown.
Inheritance is X-chromosomal dominant. Signs and symptoms are as below:
Malepatientshave blurring of vision associated with: • Cornealcloudingsince birth ranging from a diffuse
haze to a ground-glass, milky appearance. • Moon crater-like endothelial changes.
• Subepithelial band keratopathy combined with moon crater-like endothelial changes.
• Nystagmus may be associated. Femalepatientsare asymptomatic having only moon crater-like endothelial changes.

ECTATIC CONDITIONS OF CORNEA

KERATOCONUS
Keratoconus (conical cornea) (Fig. 6.29A to C) is a non-inflammatory bilateral (85%) ectatic condition of cornea in its axial part. It usually starts at puberty and progresses slowly.
Etiopathogenesis. It is still not clear. Various theories proposed so far label it as developmental condition,degenerative condition, hereditary dystrophy and endocrine anomaly.
Essential pathological changes are progressive thinning and ectasia which occur as a result of defective synthesis of mucopolysaccharide and collagen tissue. Clinical features. Symptoms. Patient presents with a defective vision due to progressive myopia and irregular astigmatism, which does not improve fully despite full correction with glasses.
132	Section III   Diseases of Eye












A






B












C
Fig. 6.29 Keratoconus showing: A, Diagrammatic depiction of configuration of cone-shaped cornea; B, Irregular circles on Placido disc examination; C, Clinical photograph (note Munson’s sign)
Signs. Following signs may be elicited: 1. Window reflex is distorted.
2. Placidodiscexaminationshows irregularity of the circles (Fig. 6.29B).
3. Slit-lamp examination may show thinning and ectasia of central cornea, opacity at the apex and Fleischer’s ring at the base of cone, folds in Descemet’s and Bowman’s membranes. Very fine, vertical, deep stromal striae (Vogt lines) which disappear with external pressure on the globe are peculiar feature.
4. On retinoscopy a yawning reflex (scissor reflex) and high oblique or irregular astigmatism is obtained.
5. Ondistantdirectophthalmoscopyan annular dark shadow (due to total internal reflection of light) is seen which separates the central and peripheral areas of cornea (oil droplet reflex).

6. Munson’ssign,i.e., localised bulging of lower lid when patient looks down is positive in late stages (Fig. 6.29C).
7. Keratometry.Normal average keratometric values are 45 D. In keratoconus keratometric values are increased and based on it the severity of keratoconus is graded as: mild (< 48 D), moderate (48–54 D), and severe (>54 D).
8. Cornealtopography,i.e., study of shape of corneal surface, is the most sensitive method for detecting early keratoconus, Forme fruste refers to the earliest subclinical form of keratoconus detected on topography.
Morphological classification. Depending upon the size and shape of the cone, the keratoconus is of three types:
• Nipple cone has a small size (<5 mm) and steep curvature.
• Ovalconeis larger (5–6 mm) and ellipsoid in shape. • Globus cone is very large (>6 mm) and globe like. Complications. Keratoconus may be complicated by development of acute hydrops due to rupture of Descemet’s membrane. The condition is characterized by sudden development of corneal oedema associated with marked defective vision, pain, photophobia and lacrimation.
Associations. Keratoconus may be associated with: • Ocular conditions e.g., ectopia lentis, congenital
cataract, aniridia, retinitis pigmentosa, and vernal keratoconjunctivitis (VKC).
• Systemicconditionse.g., Marfan’s syndrome, atopy, Down’s syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta and mitral valve prolapse.
Treatment modalities include:
1. Spectacle correction may improve vision in early cases. However, later in the course of disease the falling vision may not be corrected by glasses due to irregular astigmatism.
2. Contact lenses (rigid gas permeable) usually improve the vision in early cases. In early to moderate cases a specially designed scleral contact lens (Rose-K) may be useful.
3. Intacs, the intracorneal ring segments, are reported to be useful in early to moderate cases.
4. Cornealcollagencrosslinkingwith riboflavin (CXL or C3R) and UV-A rays may slow the progression of disease.
5. Keratoplasty may be required in later stages. Deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK) may be performed.
KERATOGLOBUS
It is a familial and hereditary bilateral congenital disorder characterised by thinning and hemispherical
Chapter 6	Diseases of Cornea	133















Fig. 6.30 Keratoglobus
protrusion of the entire cornea (Fig. 6.30). It is non-progressive and inherited as an autosomal recessive trait. It must be differentiated from congenital buphthalmos, where increased corneal size is associated with raised intraocular pressure, angle anomaly and/or cupping of optic disc.
KERATOCONUS POSTERIOR
In this extremely rare condition there is slight cone-like bulging of the posterior surface of the cornea. It is non-progressive.

ABNORMALITIES OF CORNEAL TRANSPARENCY
Normal cornea is a transparent structure. Any condition which upsets its anatomy or physiology causes loss of its transparency to some degree.
Common causes of loss of corneal transparency are: • Corneal oedema
• Drying of cornea
• Depositions on cornea
• Inflammations of cornea • Corneal degenerations
• Dystrophies of cornea
• Vascularization of cornea
• Scarring of cornea (corneal opacities).
Most of the conditions responsible for decreased transparency of cornea have been described earlier.
However, some important symptomaticconditions ofthecorneasuch as corneal oedema, corneal opacity and vascularization of cornea are described here.
CORNEAL OEDEMA
The water content of normal cornea is 78%. It is kept constant by a balance of factors which draw water in the cornea (e.g., intraocular pressure and swelling pressure of the stromal matrix = 60 mm of Hg) and the factors which draw water out of cornea (viz. the active pumping action of corneal endothelium, and

the mechanical barrier action of epithelium and endothelium).
Disturbance of any of the above factors leads to corneal oedema, wherein its hydration becomes above 78%, central thickness increases and transparency reduces.
Causes of corneal oedema
1. Raised intraocular pressure 2. Endothelial damage
• Due to injuries, such as birth trauma (forceps delivery), surgical trauma during intraocular operation, contusion injuries and penetrating injuries.
• Endothelial damage associated with corneal dystrophies such as, Fuchs dystrophy, congenital hereditary endothelial dystrophy and posterior polymorphous dystrophy.
• Endothelial damage secondary to inflammations such as uveitis, endophthalmitis and corneal graft infection.
3. Epithelial damage due to: • mechanical injuries,
• chemical burns,
• radiational injuries, • thermal injuries,
• inflammation and infections.

Clinical features
Initially there occurs stromal haze with reduced vision. In long-standing cases with chronic endothelial failure (e.g., in Fuch’s dystrophy) there occurs permanent oedema with epithelial vesicles and bullae formation (bullouskeratopathy).This is associated with marked loss of vision, pain, discomfort and photophobia, due to periodic rupture of bullae.
Treatment
1. Treatthecausewherever possible, e.g., raised IOP and ocular inflammations.
2. Dehydration of cornea may be tried by use of:
• Hypertonic agents e.g., 5% sodium chloride drops or ointments or anhydrous glycerine may provide sufficient dehydrating effect.
• Hot forced air from hair dryer may be useful.
3. Therapeutic soft contact lenses may be used to get relief from discomfort of bullous keratopathy.
4. Penetrating keratoplasty is required for long-standing cases of corneal oedema, non-responsive to conservative therapy.
CORNEAL OPACITY
The word ‘corneal opacification’ literally means loss of normal transparency of cornea, which can
134	Section III   Diseases of Eye


occur in many conditions. Therefore, the term ‘corneal opacity’ is used particularly for the loss of transparency of cornea due to scarring.
Causes
1. Congenital opacities may occur as developmental anomalies or following birth trauma.
2. Healed corneal wounds. 3. Healed corneal ulcers.
Clinical features
Corneal opacity may produce loss of vision (when dense opacity covers the pupillary area) or blurred vision (due to astigmatic effect).
Types of corneal opacity
Depending on the density, corneal opacity is graded as nebula, macula and leucoma.
1. Nebular corneal opacity. It is a faint opacity which results due to superficial scars involving Bowman’s layer and superficial stroma (Figs. 6.31A and 6.32A). A thin, diffuse nebula covering the pupillary area interferes more with vision than the localised leucoma away from pupillary area. Further, the nebula produces more discomfort to patient due to blurred image owing to irregular astigmatism than the leucoma which completely cuts off the light rays.













A












C











Fig. 6.31 Diagrammatic depiction of corneal opacity: A, Nebular; B, Macular: C, Leucomatous; D, Adherent leucoma


2. Macular corneal opacity. It is a semi-dense opacity produced when scarring involves about half the corneal stroma (Figs. 6.31B and 6.32B).
3. Leucomatous corneal opacity (leucoma simplex). It is a dense white opacity which results due to scarring of more than half of the stroma (Figs. 6.31C and 6.32C). 4. Adherent leucoma. It results when healing occurs after perforation of cornea with incarceration of iris (Figs. 6.31D and 6.32D).
5. Corneal facet. Sometimes, the corneal surface is depressed at the site of healing (due to less fibrous tissue); such a scar is called facet.













B












D

Fig. 6.32 Clinical photographs of corneal opacity: A, Nebular; B, Macular; C, Leucomatous; D, Adherent leucoma
Chapter 6	Diseases of Cornea	135


6. Kerectasia. In this condition, corneal curvature is increased at the site of opacity (bulge due to weak scar).
7. Anterior staphyloma. An ectasia of pseudocornea (the scar formed from organised exudates and fibrous tissue covered with epithelium) which results after total sloughing of cornea, with iris plastered behind it is called anterior staphyloma (Figs. 6.33A and B).
Secondary changes in corneal opacity  which may be seen in long-standing cases include: hyaline degeneration, calcareous degeneration, pigmentation and atheromatous ulceration.
Treatment
1. Optical iridectomy. It may be performed in cases with central macular or leucomatous corneal opacities, provided vision improves with pupillary dilatation.


















A












B

Fig. 6.33 Anterior staphyloma: A, Diagrammatic cross-section; B, Clinical photograph

2. Phototherapeutic keratectomy (PTK) performed with excimer laser is useful in superficial (nebular) corneal opacities.
3. Keratoplasty provides good visual results in uncomplicated cases with corneal opacities, where optical iridectomy is not of much use.
4. Cosmetic coloured contact lens gives very good cosmetic appearance in an eye with ugly scar having no potential for vision. Presently, this is considered the best option, even over and above the tattooing for cosmetic purpose.
5. Tattooing of scar. It was performed for cosmetic purposes in the past. It is suitable only for firm scars in a quiet eye without useful vision. For tattooing Indian black ink, gold or platinum may be used. To perform tattooing, first of all, the epithelium covering the opacity is removed under topical anaesthesia (2% or 4% xylocaine). Then a piece of blotting paper of same size and shape, soaked in 4% gold chloride (for brown colour) or 2% platinum chloride (for dark colour) is applied over it. After 2–3 minutes, the piece of filter paper is removed and a few drops of freshly prepared 2% hydrazine hydrate solution are poured over it. Lastly, eye is irrigated with normal saline and patched after instilling antibiotic and atropine eye ointment. Epithelium grows over the pigmented area.
CORNEAL VASCULARIZATION
Normal cornea is avascular except for small capillary loops which are present in the periphery for about 1 mm. In pathological states, it can be invaded by vessels as a defence mechanism against the disease or injury. However, vascularization interferes with corneal transparency and occasionally may be a source of irritation.
Pathogenesis
Pathogenesis of corneal vascularization is still not clear. It is presumed that mechanical and chemical factors play a role.
Vascularization is normally prevented by the compactness of corneal tissue. Probably, due to some vasoformative stimulus (chemical factor) released during pathological states, there occurs proliferation of vessels which invade from the limbus; when compactness of corneal tissue is loosened (mechanicalfactor) due to oedema (which may be traumatic, inflammatory, nutritional, allergic or idiopathic in nature).
Clinico-etiological features
Clinically, corneal vascularization may be superficial or deep.
1.  Superficial corneal vascularization. In it vessels are arranged usually in an arborising pattern,
136	Section III   Diseases of Eye


present below the epithelial layer and their continuity can be traced with the conjunctival vessels (Fig. 6.34A).
■Common causes of superficial corneal vascula-rization are: trachoma, phlyctenular kerato-conjunctivitis, superficial corneal ulcers and rosacea keratitis.
■Pannus. When extensive superficial vascularization is associated with white cuff of cellular infiltration, it is termed as pannus.In progressive pannus, corneal infiltration is ahead of vessels while in regressive pannus it lags behind.
2. Deep vascularization. In this vessels are generally derived from anterior ciliary arteries and lie in the corneal stroma. These vessels are usually straight, not anastomosing and their continuity cannot be traced beyond the limbus. Deep vessels may be arranged as terminal loops (Fig. 6.34B), brush (Fig. 6.34C), parasol, umbel (Fig. 6.34D), network or interstitial arcade. ■Common causes of deep vascularization are: interstitial keratitis, disciform keratitis, deep corneal ulcer, chemical burns, sclerosing keratitis and corneal grafts.
Treatment
Treatment of corneal vascularization is usually unsatisfactory. Vascularization may be prevented by timely and adequate treatment of the causative conditions.
• Corticosteroids may have vasoconstrictive and suppressive effect on permeability of capillaries.




















Fig. 6.34 Corneal vascularization : A, Superficial; B, Terminal loop type; C, Brush type; D, Umbel type

• Application of irradiation is more useful in superficial than the deep vascularization.
• Surgicaltreatmentin the form of peritomy may be employed for superficial vascularization.

CORNEAL SURGERY

KERATOPLASTY
Keratoplasty, also called corneal grafting or corneal transplantation, is an operation in which the patient’s diseased cornea is replaced by the healthy clear cornea.
Types
A. Autokeratoplasty, which can be:
1. Rotational keratoplasty, in which patient’s own cornea is trephined and rotated to transfer the pupillary area having a small corneal opacity to the periphery.
2. Contralateral keratoplasty. It is indicated when cornea of one eye of the patient is opaque and the other eye is blind due to posterior segment disease (e.g., optic atrophy and retinal detachment, etc.) with clear cornea. In contralateral autokeratoplasty cornea of the two eyes are exchanged with each other.
B. Allografting or Allo-keratoplasty. In it, patient’s diseased cornea is replaced by the donor’s healthy cornea. It can be of following types:
1. Penetrating Keratoplasty (PK) (full-thickness-grafting)
2. LamellarKeratoplasty(partial-thickness grafting) which may be:
• Deep anterior lamellar keratoplasty (DALK). It is performed when endothelium and Descemet’s membrane are normal e.g. keratoconus.
• Descemet’s stripping endothelial keratoplasty (DSEK). It is performed when only endothelium is defective e.g. after the surgical trauma during phacoemulsification.
3. Small patch graft (for small defects), which may be full thickness or partial thickness.
Indications
1. Optical, i.e., to improve vision. Important indications are: corneal opacity, bullous keratopathy, corneal dystrophies, advanced keratoconus.
2. Therapeutic, i.e., to replace inflamed cornea not responding to conventional therapy.
3. Tectonicgrqft,i.e., to restore integrity of eyeball e.g. after corneal perforation and in marked corneal thinning.
4. Cosmetic, i.e., to improve the appearance of the eye.
Chapter 6	Diseases of Cornea	137


Donor tissue
The donor eye should be removed as early as possible (within 6 hours of death). It should be stored under sterile conditions.
Evaluation of donor cornea.  Biomicroscopic examination of the whole globe, before processing the tissue for media storage, is very important. The donor corneal tissue is graded into excellent, very good, good, fair, and poor depending upon the condition of corneal epithelium, stroma, Descemet’s membrane and endothelium (Table 6.1).
Methods of corneal preservation
1. Short-term storage (up to 48 hours). The whole globe is preserved at 4° C in a moist chamber.
2. Intermediate storage (up to 2 weeks) of donor cornea can be done in McCarey-Kaufman (MK) medium and various chondroitin sulfate enriched media such as optisol medium.
3. Long-termstorageup to 35 days is done by organ culture method or by cryopreservation at –70°C.

Surgical technique of penetrating keratoplasty
1. Excision of donor corneal button. The donor corneal button should be cut 0.25 mm larger than the recipient, taking care not to damage the endothelium. Donor cornea is placed in a tephlon block and the button is cut with the help of a trephine from the endothelial side (Fig. 6.35A).
2. Excisionofrecipientcornealbutton.With the help of a corneal trephine (7.5 mm to 8 mm in size) a partial thickness incision is made in the host cornea (Fig. 6.35B). Then, anterior chamber is


entered with the help of a razor blade knife and excision is completed using corneoscleral scissors (Fig. 6.35C).
3. Suturing of corneal graft into the host bed (Fig. 6.35D) is done with either continuous (Fig. 6.35E) or interrupted (Fig. 6.35F) 10–0 nylon sutures.
Complications
1. Early complications. These include flat anterior chamber, iris prolapse, infection, secondary glaucoma, epithelial defects and primary graft failure.
2. Latecomplications.These include graft rejection, recurrence of disease and astigmatism.
Graft rejection
It refers to the immunological response of the host to the donor corneal tissue. It can occur as early as 2 weeks and upto several years after grafting. Graft rejection is classically believed to be a delayed type of hypersensitivity response.
Risk factorsinclude younger age of recipient, previous graft failure, corneal vascularization, larger graft size, donor epithelium and massive blood transfusion. Clinical presentations include:
■Epithelial rejection characterized by an elevated epithelial rejection line which stains with fluorescein. ■Subepithelial infiltrates known as Kayes dots. ■Stromalrejectionis characterized by sudden onset of full thickness stromal haze in a previously clear graft.
■Endothelial rejection may present as:
• Khodadaust line demarcating healthy and damaged endothelium.
• Diffuse endothelial rejection with lot of Keratic precipitates.



Table 6.1 Grading of donor cornea on slit-lamp biomicroscopic examination

Grade of donor corneal tissue

Parameter

Epithelial defects and haze
Corneal stromal clarity
Arcus senilis

Descemet’s membrane
Endothelium

Grade I (Excellent)
None


Crystal clear

None

No folds

No defect

Grade II (Very good)
Slight epithelial haze or defects

Clear

Slight

Few shallow folds

No defect

Grade III (Good)
Obvious moderate epithelial defects
Slight cloudiness

Moderate (<2.5 mm)
Numerous shallow folds
Few vacuolated cells

Grade IV (Fair)



Moderate cloudiness
Heavy
(>2.5 mm – 4 mm)
Numerous deep folds
Moderate guttate

Grade V (Poor)



Marked cloudiness
Very heavy (>4 mm)
Marked deep folds
Marked guttate
138	Section III   Diseases of Eye

























Fig. 6.35 Technique of keratoplasty: A, Excision of donor corneal button; B & C, Excision of recipient corneal button; D, Suturing of donor button into recipient’s bed; E, Showing pattern of continuous sutures in keratoplasty; F, Clinical photograph of a patient with interrupted sutures in keratoplasty



REFRACTIVE CORNEAL SURGERY Refractive corneal surgery includes:
• Radial Keratotomy (RK),
• Astigmatic Keratotomy (AK),
• Photorefractive Keratotomy (PRK),
• Laser assisted in situ Keratomileusis (LASIK) and its varieties,
• Thermal Laser Keratoplasty (TLK), • Conductive Keratoplasty (CK),
• Orthokeratoplasty, and
• Intracorneal Ring (ICR) implants (For details see page 52 to 55).

PHOTOTHERAPEUTIC KERATECTOMY Phototherapeutic Keratectomy (PTK) refers to the ablation of superficial corneal lesion with the help of excimer laser (198 nm).
Indications include:
• Superficial corneal scars,
• Corneal degenerations, e.g. band-shaped Keratopathy, Salzman nodular degeneration and oil droplet keratopathy,


• Epithelial  dystrophies  (e.g.  Reis-Buckler dystrophy), and
• Recurrent corneal erosions.
Procedure. The modern excimer laser machines have two modes for PTK:
• Spot mode, where a small spot (<1 mm) can be ablated, and
• Shappingmode,which allows uniform removal of corneal tissue from a large zone.
Contraindications include: • Excessive thin corneas,
• Moderate to severe dry eye, and • Deep corneal lesions.
Complications. Faint corneal haze is a usual end result of the PTK. Other complications include:
• Secondary infections,
• Induced hypermetropia, and • Secondary keractesia.
KERATOPROSTHESIS
Keratoprosthesis refers to an artificial corneal device used in patients unsuitable for keratoplasty.
Chapter 6	Diseases of Cornea	139


Types. Keratoprosthesis basically consists of a central optical cylindrical part made of poly-methylmethaacrylate (PMMA). Based on the surrounding fixation device, the commonly used keratoprosthesis of various designs are as below:
• Boston keratoprosthesis (6.36A) consists two plates and one cylinder. It is fixed using the donor cornea.
• Alfa cor keratoprosthesis (6.36B) consists of an outer porous skirt made up of high water content PHEMA and a transparent central optic made from low water content PHEMA. An interpenetrating polymer network (IPN), which is a junction zone between the skirt and central optic and serve as a permanent bond. It has a refractive power close to that of human cornea.
• Osteo-odonto-keratoprosthesis (Fig. 6.36C) is fixed with the help of patients own tooth root and alveolar bone.
• Chondro-keratoprosthesis is fixed with patients own cartilage.
• Onycho-keratoprosthesis is fixed with patient’s nails.
• Stanford keratoprosthesis is a recently introduced device which incorporates the grafting of bio-active factors with a change in the bulk material design.
• Singh and Worst collar-stud keratoprosthesis is fixed with stainless steel sutures.
Indications. Prerequisites for keratoprosthesis include bilateral blindness due to corneal diseases (not suitable for keratoplasty) with accurate perception of light, normal electrophysiological tests and absence of gross posterior segment disorders on ultrasonography, e.g:
• Stevens-Johnson syndrome, • Chemical burns,
• Ocular cicatricial pemphigoid, • Severe trachoma
• Multiple previous failed corneal grafts. Complications include:
• Extrusion of prosthesis,












A










B










C

Fig. 6.36 Keratoprosthesis: A, Boston; B, Alfa cor; C, Osteo-odonto


• Intractable glaucoma,
• Retroprosthetic membrane formation, • Uveitis, and
• Retinal detachment.
7

Diseases of Sclera



Chapter Outline


APPLIED ANATOMY Thickness Apertures
Microscopic structure INFLAMMATIONS
•
•
•
•
•
Episcleritis Scleritis



APPLIED ANATOMY

Sclera forms the posterior five-sixth opaque part of the external fibrous tunic of the eyeball. Its whole outer surface is covered by Tenon’s capsule. In the anterior part it is also covered by bulbar conjunctiva. Its inner surface lies in contact with choroid with a potential suprachoroidal space in between. In its anterior most part near the limbus there is a furrow which encloses the canal of Schlemm.
Thickness of sclera varies considerably in different individuals and with the age of the person. It is generally thinner in children than the adults and in females than the males. Sclera is thickest posteriorly (1 mm) and gradually becomes thin when traced anteriorly. It is thinnest at the insertion of extraocular muscles (0.3 mm). Lamina cribrosa is a sieve-like sclera from which fibres of optic nerve pass. Apertures. Sclera is pierced by three sets of apertures (Fig. 7.1).
1. Posterior apertures are situated around the optic nerve and transmit long and short ciliary nerves and vessels.
2. Middle apertures (four in number) are situated slightly posterior to the equator; through these pass the four vortex veins (vena verticosae).
3. Anterior apertures are situated 3 to 4 mm away from the limbus. Anterior ciliary vessels and branches from long ciliary nerves pass through these apertures.

BLuE ScLErA
STAPHYLOMAS
• Anterior staphyloma Intercalary staphyloma Ciliary staphyloma Equatorial staphyloma Posterior staphyloma
•
•
•
•



Microscopic structure. Histologically, sclera consists of following three layers:
1. Episcleral tissue. It is a thin, dense vascularised layer of connective tissue which covers the sclera proper. Fine fibroblasts, macrophages and lymphocytes are also present in this layer.
2. Sclera proper. It is an avascular structure which consists of dense bundles of collagen fibres. The bands of collagen tissue cross each other in all directions.

















Fig. 7.1 Apertures in the sclera. (posterior view): SCN, short ciliary nerve; SPCA, short posterior ciliary artery; LPCA, long posterior ciliary artery; VC, vena verticosa
Chapter 7	Diseases of Sclera	141

3. Lamina fusca. It is the innermost part of sclera which blends with suprachoroidal and supraciliary laminae of the uveal tract. It is brownish in colour owing to the presence of pigmented cells.
Nerve supply. Sclera is supplied by branches from the long ciliary nerves which pierce it 2–4 mm from the limbus to form a plexus.

INFLAMMATIONS OF SCLERA


EpisclEritis
Episcleritis is benign recurrent inflammation of the episclera, involving the overlying Tenon’s capsule but not the underlying sclera. It typically affects young adults, being twice as common in women than men.
Etiology
1. Idiopathic. Exact etiology is not known in many cases.
2. Systemic diseases associated with episcleritis, include gout, rosacea, psoriasis and connective tissue diseases.
3. Hypersensitivity  reaction to endogenous tubercular or streptococcal toxins is also reported.
4. Infectious episcleritis may be caused by herpes zoster virus, syphillis, Lyme disease and tuberculosis.
pathology



A












B
Fig. 7.2 Episcleritis: A, Diffuse; B, Nodular



Histologically, there occurs localised lymphocytic infiltration of episcleral tissue associated with oedema and congestion of overlying Tenon’s capsule and conjunctiva.
clinical features
Symptoms. Episcleritis is characterised by redness, mild ocular discomfort described as gritty, burning or foreign body sensation. Many a time it may not be accompanied by any discomfort at all. Rarely, mild photophobia and lacrimation may occur.
Signs.  On examination two clinical types of episcleritis, simple and nodular may be recognised. Episclera is seen acutely inflamed in the involved area.
• Simple episcleritis is characterised by sectorial (occasionally diffuse) inflammation of episclera. The engorged episcleral vessels are large and run in radial direction beneath the conjunctiva (Fig. 7.2A).
• Nodular episcleritis is characterised by a pink or purple flat nodule surrounded by injection, usually situated 2–3 mm away from the limbus (Fig. 7.2B). The nodule is firm, tender, can be


moved separately from the sclera and the overlying conjunctiva also moves freely.
Clinical course. Episcleritis runs a limited course of 10 days to 3 weeks and resolves spontaneously. However, recurrences are common and tend to occur in bouts. Rarely, a fleeting type of disease (episcleritis periodica) may occur.
Differential diagnosis
• Simple episcleritis may be confused rarely with conjunctivitis.
• Nodular episcleritis may be confused with inflamed pinguecula, swelling and congestion due to foreign body lodged in bulbar conjunctiva and, very rarely with scleritis.
treatment
1. Topical NSAIDs,e.g., ketorolac 0.3% may be useful. 2. Topical mild corticosteroid eyedrops e.g., fluorometholone or loteprednol instilled 2–3 hourly, render the eye more comfortable and
resolve the episcleritis within a few days.
3. Topical artificial tears e.g., 0.5% carboxy methyl cellulose have soothing effect.
142	Section iii   Diseases of Eye


4. Cold compresses applied to the closed lids may offer symptomatic relief from ocular discomfort.
5. Systemic nonsteroidal anti-inflammatory drugs (NSAIDs) such as flurbiprofen (300 mg OD), indomethacin (25 mg three times a day), or oxyphenbutazone may be required in recurrent cases.
sclEritis
Scleritis refers to a inflammation of the sclera proper. It is a comparatively serious disease which may cause visual impairment and even loss of the eye if treated inadequately. Fortunately, its incidence is much less than that of episcleritis. It usually occurs in elderly patients (40-70 years) involving females more than the males.
Etiology
Overall about 50% cases of scleritis are associated with some systemic diseases, most common being connective tissue diseases.
common conditions are as follows:
1. Autoimmune collagen disorders, especially rheumatoid arthritis, is the most common association. About 0.5% of patients (1 in 200) suffering from seropositive rheumatoid arthritis develop scleritis. Other associated collagen disorders are Wegener’s granulomatosis, polyarteritis nodosa (PAN), systemic lupus erythematosus (SLE) and ankylosing spondylitis.
2. Metabolic disorders like gout and thyrotoxicosis have also been reported to be associated with scleritis.
3. Some infections, particularly herpes zoster ophthalmicus, chronic staphylococcal and streptococcal infection have also been known to cause infectious scleritis.
4. Granulomatous diseases like tuberculosis, syphilis, sarcoidosis, leprosy can also cause scleritis.
5. Miscellaneous conditions like irradiation, chemical burns, Vogt-Koyanagi-Harada syndrome, Behcet’s disease and rosacea are also implicated in the etiology.
6. Surgically induced scleritis (SIS) is a rare complication of ocular surgery. It occurs within 6 months postoperatively. Exact mechanism not known, may be precipitation of underlying systemic cause.
7. Idiopathic. In many cases of scleritis, cause is unknown.
pathology
Histopathological changes are that of a chronic granulomatous disorder characterised by fibrinoid necrosis, destruction of collagen together with infiltration by polymorphonuclear cells, lymphocytes, plasma cells and macrophages. The granuloma is

surrounded by multinucleated epithelioid giant cells and old and new vessels, some of which may show evidence of vasculitis.
classification
Scleritis can be classified as follows: A. Non-infectious scleritis
I. Anterior scleritis (98%)
a. Non-necrotizing scleritis (85%) 1. Diffuse
2. Nodular
b. Necrotizing scleritis (13%) 1. with inflammation
2. without inflammation (scleromalacia perforans)
II. Posterior scleritis (2%) B. Infectious scleritis
clinical features Symptoms
■Pain: Patients complain of moderate to severe pain which is deep and boring in character and often wakes the patient early in the morning. Ocular pain radiates to the jaw and temple.
■Redness may be localized or diffuse. ■Photophobia and lacrimation may be mild to
moderate.
■Diminution of vision may occur occasionally.
Signs

A. Non-infectious scleritis
Salient features of different clinical types of non-infectious scleritis are as below:
I. Anterior scleritis
a. Non–necrotizing anterior scleritis
1. Non-necrotizing anterior diffuse scleritis. It is the commonest variety, characterised by widespread inflammation involving a quadrant or more of the anterior sclera. The involved area is raised and salmon pink to purple in colour (Fig. 7.3).














Fig. 7.3 Non-necrotizing anterior diffuse scleritis
Chapter 7	Diseases of Sclera	143


2. Non-necrotizing anterior nodular scleritis. It is characterised by one or two hard, purplish elevated immovable scleral nodules, usually situated near the limbus (Fig. 7.4). Sometimes, the nodules are arranged in a ring around the limbus (annular scleritis).
b. Necrotizing anterior scleritis
1. Anterior necrotizing scleritis with inflammation. It is an acute severe form of scleritis characterised by intense localised inflammation associated with areas of infarction due to vasculitis (Fig. 7.5). The affected necrosed area is thinned out and sclera becomes transparent and ectatic with uveal tissue shining through it. It is usually associated with anterior uveitis. 2. Anterior necrotizing scleritis without inflammation (scleromalacia perforans). This specific entity typically occurs in elderly females usually suffering from long-standing rheumatoid arthritis. It is characterised by development of yellowish patch of melting sclera (due to obliteration of arterial supply); which often together with the overlying episclera and conjunctiva completely separates from the surrounding normal sclera. This sequestrum of sclera becomes dead white













Fig. 7.4 Non-necrotizing anterior nodular scleritis















Fig. 7.5 Anterior necrotizing scleritis with inflammation

in colour, which eventually absorbs leaving behind it a large punched out area of thin sclera through which the uveal tissue shines (Fig. 7.6). Spontaneous perforation is extremely rare.

II. Posterior scleritis.
It is an inflammation involving the sclera behind the equator. The condition is frequently misdiagnosed. It is characterised by features of associated inflammation of adjacent structures, which include: exudative retinal detachment, macular oedema, proptosis and limitation of ocular movements.

B. Infectious scleritis
• Infectious scleritis accounts for 5–10% of all cases. • In the early stage diagnosis becomes difficult as
presentation is similar to as non-infectious scleritis. • Scleritis with purulent exudates (Fig. 7.7) or
infiltrates should raise the suspicion of an infectious etiology.
• Formation of fistulae, painful nodules, conjunctival and scleral ulcers are usually the   signs of infectious scleritis.













Fig. 7.6 Anterior necrotizing scleritis without inflammation (Scleromalacia perforans)














Fig. 7.7 Infectious scleritis
144	Section iii   Diseases of Eye


complications
These are quite common with necrotizing scleritis and include sclerosing keratitis, keratolysis, complicated cataract and secondary glaucoma.

investigations
Following laboratory studies may be helpful in identifying associated systemic diseases or in establishing the nature of immunologic reaction:
1. TLc, DLc and ESR.
2. Serum levels of complement (c3), immune complexes, rheumatoid factor, antinuclear antibodies and L.E cells for an immunological survey.
3. FTA–ABS, VDRL for syphilis. 4. Serum uric acid for gout.
5. Urine analysis. 6. Mantoux test.
7. X-rays of chest, paranasal sinuses, sacroiliac joint and orbit (to rule out foreign body especially in patients with nodular scleritis).
treatment
A. Non-infectious scleritis
I. Non-necrotizing scleritis. It is treated by: • Topical steroid eyedrops
• Systemic indomethacin 75 mg twice a day until inflammation resolves.
II. Necrotizing scleritis. It is treated by: • Topical steroids
• Oral steroids on heavy doses, tapered slowly.
• Immunosuppressive agents like methotrexate or cyclophosphamide may be required in non-responsive cases.
• Subconjunctival steroids are contraindicated because they may lead to scleral thinning and perforation.
• Surgical treatment, in the form of scleral patch graft may be required to preserve integrity of the globe in extensive scleral melt and thinning.
B. Infectious scleritis
• Most of the time diagnosis is delayed and patients are put on topical and oral steroids which worsen the infective scleritis.
• Antimicrobial therapy, both with topical and oral agents is required in an aggressive manner.
• Surgical debridementis found useful by debulking the infected scleral tissue and also facilitating the effect of antibiotics.

BluE sclErA
It is an asymptomatic condition characterised by marked, generalised blue discoloration of sclera due to thinning (Fig. 7.8). It is typically associated















Fig. 7.8 Blue sclera

with osteogenesis imperfecta. Its other causes are Marfan’s syndrome, Ehlers-Danlos syndrome, pseudoxanthoma elasticum, buphthalmos, high myopia and healed scleritis.

STAPHYLOMAS

Staphyloma refers to a localised bulging of weak and thin outer tunic of the eyeball (cornea or sclera), lined by uveal tissue which shines through the thinned out fibrous coat.
types
Anatomically, it can be divided into anterior, intercalary, ciliary, equatorial and posterior staphyloma (Fig. 7.9). 1. Anterior staphyloma (see page 135).
2. Intercalary staphyloma. It is the name given to the localised bulge in limbal area lined by root of iris (Figs. 7.9A and 7.10).
• It results due to ectasia of weak scar tissue formed at the limbus, following healing of a perforating injury or a peripheral corneal ulcer.
• Secondary angle closure glaucoma, may cause progression of bulge if not treated.
• Defective vision occurs due to marked corneal astigmatism.
Treatment consists of localised staphylectomy under heavy doses of oral steroids.
3. Ciliary staphyloma. As the name implies, it is the bulge of weak sclera lined by ciliary body. It occurs about 2–3 mm away from the limbus (Figs. 7.9B and 7.11). Its common causes are thinning of sclera following perforating injury, scleritis and absolute glaucoma.
4. Equatorial staphyloma. It results due to bulge of sclera lined by the choroid in the equatorial region (Fig. 7.9c). Its causes are scleritis and degeneration of sclera in pathological myopia. It occurs more
Chapter 7	Diseases of Sclera	145
















A





Fig. 7.9 Staphylomas (diagrammatic depiction) A, Intercalary; B, Ciliary; C, Equatorial; D, Posterior









B
Fig. 7.12  Fundus photograph (A) and diagrammatic depiction (B) of excavation of retinal tissue and blood vessels in posterior staphyloma

Fig. 7.10 Intercalary staphyloma


commonly at the regions of sclera which are perforated by vortex veins.
5. Posterior staphyloma. It refers to bulge of weak sclera lined by the choroid behind the equator (Fig. 7.9D). Here again the common causes are pathological myopia, posterior scleritis and perforating injuries. It is diagnosed on ophthalmoscopy. The area is excavated with retinal vessels dipping in it (just like marked cupping of optic disc in glaucoma) (Fig. 7.12). Its floor is focussed with minus lenses in ophthalmoscope as compared to its margins.
Fig. 7.11 Ciliary staphyloma
8

Diseases of Uveal Tract



CHAPTER OUTLINE

APPLIED ANATOMY Iris
Ciliary body Choroid
•
•
•
•
Blood supply of uveal tract
CONGENITAL ANOMALIES OF UVEAL TRACT Heterochromia of iris
•
•
•
Corectopia
Congenital coloboma of uveal tract
UVEITIS
General considerations Definition Classification
•
•
•
Etiology



APPLIED ANATOMY

Uveal tissue constitutes the middle vascular coat of the eyeball. From anterior to posterior, it can be divided into three parts, namely, iris, ciliary body and choroid. However, the entire uveal tract is developmentally, structurally and functionally one indivisible structure.
THE IRIS
Iris is the anterior most part of the uveal tract. It is a thin circular disc corresponding to the diaphragm of a camera. In its centre is an aperture of about 4 mm diameter called pupil which regulates the amount of light reaching the retina. At periphery, the iris is attached to the middle of anterior surface of the ciliary body. It divides the space between the cornea and lens into anterior and posterior chambers.
Macroscopic appearance
Anterior surface of the iris can be divided into a ciliary zone and a pupillary zone by a zigzag line called collarette (Fig. 8.1).
1. Ciliary zone. It presents series of radial streaks due to underlying radial blood vessels and crypts

• Pathology
Non-suppurative uveitis Anterior uveitis (Iridocyclitis) Intermediate uveitis Posterior uveitis
•
•
•
•
Specific clinico-etiological types of non-suppurative uveitis Purulent uveitis
•
•
Endophthalmitis Panophthalmitis
DEGENERATIVE CONDITIONS Degenerations of the Iris
•
•
Degenerations and dystrophies of the choroid TUMOURS
•
•
•
Of choroid
Of ciliary body Of iris



which are depressions where superficial layer of iris is missing. Crypts are arranged in two rows—the peripheral present near the iris root and the central present near the collarette.
2. Pupillary zone. This part of the iris lies between the collarette and pigmented pupillary frill and is relatively smooth and flat.















Fig. 8.1  Macroscopic appearance of anterior surface of iris
Chapter 8	Diseases of Uveal Tract	147