CORNEAL DISORDERS

Congenital abnormalities of cornea, include:

Megalocornea, i.e. a corneal size of gt;12 mm, may be an isolated defect or associated with Marfan syndrome, craniosynostosis and osteogenesis imperfecta.

Microcornea, i.e. a corneal size of lt;6 mm or smaller than opposite side, is an indicator of intrauterine infections, e.g. congenital rubella syndrome or chromosomal disorders, though some cases may be familial. It is rarely an isolated defect, often associated with microphthalmia, cataracts and retinal abnormalities.

Keratoconus, i.e. cone-shaped cornea with central thinning may be post-traumatic or associated with congenital anomalies, e.g. Down syndrome, Marfan syndrome and osteogenesis imperfecta. High myopia is common in these cases, due to increased anteriorposterior distance of visual axis.

Keratitis/corneal ulcer is a potential vision-threatening inflammation of cornea, more common and often recurrent in children with: (a) pre-existing corneal pathology, e.g. vitamin A deficiency, (b) reduced corneal sensations, e.g. Riley-Day syndrome, and (c) prolonged eye-exposure, e.g. proptosis.

Etiologically, foreign body injuries are commonest cause of keratitis in children, followed by spread from other ocular infections and vitamin A deficiency (Table 26.5).

TABLE 26.5: Causes of keratitis/corneal ulcer

1. Ocular trauma with/without secondary infection

2. Nutritional: Vitamin A deficiency

3. Local infections: Conjunctivitis, orbital cellulitis

4. Systemic infections:

Viral : Measles, HSV (Dendritic ulcer), VCZ

Bacterial : Tuberculosis (Phylectenules) Spirochetal : Syphilis

5. Developmental corneal defects/degenerations

TABLE 26.6: Causes of corneal opacities

TABLE 26.7: Common causes of uveitis

Acquired

• Vitamin A deficiency

• Traumatic: Ocular injuries, exposure keratopathy

• Inflammatory: Infective keratitis

• Glaucoma

Congenital (or since early life)

• Intrauterine infections, e.g. congenital rubella

• Perinatal eye injury (birth trauma)

• Inborn errors of metabolism, e.g.

• Others: Sclerocornea, hereditary keratopathies

MPS: Mucopolysaccharoidosis; GSD: Glycogen storage disorders.

Clinically, these cases present with photophobia, epiphora, ocular pain, circumciliary congestion and focal/diffuse corneal haze.

Diagnosis is based on slit-lamp visualization of lesion, before and after fluorescein staining and microbiological studies on corneal scrapping.

Management includes intensive topical therapy with antimicrobials and cycloplegic agents (to prevent synechiae formation), systemic antibiotics and surgical debridement in non-healing cases. Drug of choice for dendritic corneal ulcers due to HSV infection is topical 5-iodo-2-deoxyuridine (IDU).

Complications of keratitis/corneal ulcers include: (a) hypopyon, i.e. pus in anterior chamber, (b) corneal perforation and opacities, (c) posterior synechiae with secondary glaucoma, and (d) spread of infection to deeper structures, e.g. uveitis or panophthalmitis.

Corneal opacities may be congenital or acquired and focal or diffuse. In Indian children, Vitamin A deficiency and corneal injuries are two most common causes of corneal opacities (Table 26.6).

Sclerocornea is an important cause of congenital and familial corneal opacity, characterized by replacement of transparent cornea by a sclera-like tissue, specially in peripheries. Except sclerocornea and congenital rubella, other congenital keratopathies usually do not manifest at birth and develop over a period of time.

Prompt detection and treatment (keratoplasty, corneal transplant) is essential in childhood corneal opacities, to prevent development of amblyopia.

Corneal pigmentation usually indicate a metabolic disorder, e.g. presence of Kayser-Fleischer ring a golden- brown ring near the limbus in Wilson disease, refractile crystals in cystinosis and golden-brown deposits in alkaptonuria.

26.2.7