Keratomalacia

Synonym - Xerotic Keratitis

Xerophthalmia - a dry cornea - progresses to keratomalacia if left untreated. Keratomalacia occurs where the cornea becomes thin and soft and then ulcerates. This may be complicated by corneal scarring, perforation (with secondary extrusion of the eye contents), permanent deformity of the eye ball (phthisis bulbi) and blindness.
Usually occurs as a result of primary Vitamin A deficiency or defects in Vitamin A absorption or metabolism. In developed countries, may be a consequence of poor nutrition due to alcoholism¹, severe mental illness or eating disorder²or malabsorption of fat soluble vitamins (for example, cystic fibrosis, pancreatic disorders, inflammatory bowel disease, liver disease, intestinal bypass surgery).

Commonest cause of acquired paediatric blindness worldwide - accounts for 0.5 million cases worldwide³.

Risk factors:

• Primary Vitamin A deficiency - prevalent in much of the developing world. Endemic in South and East Asia where rice is the staple food.
• Protein-energy malnutrition is associated with keratomalacia - the diet is likely to be deficient in Vitamin A due to reduced intake but starvation also affects the metabolism of Vitamin A.
• May be precipitated by a systemic illness such as measles ("measles blindness" - 15,000-60,000 cases per annum⁴), pneumonia or diarrhoea.

• Night blindness (poor dark adaptation) tends to be the earliest ocular symptom of Vitamin A deficiency.
• Eyes become dry (cornea, lacrimal glands and conjunctiva all affected).
• Keratomalacia presents with bilateral central grey, indolent corneal ulcers surrounded by dull, hazy cornea, sometimes with photophobia.
• The cornea becomes soft and necrotic, usually progressing to perforation.
• Bitot's spots (foamy, wedge-shaped areas in the conjunctiva, usually temporal)⁵ are formed by epithelial debris and secretions and are strongly associated with Vitamin A deficiency especially in young children.

Plasma retinol and retinol binding proteins are suppressed in advanced Vitamin A deficiency.

• Diet: Correction of any Vitamin A deficiency with oral supplementation and diet modification.
• Surgery: Keratoplasty - limited in success.⁶

Xerophthalmia and keratomalacia are associated with increased mortality in children.
An Indonesian study showed mortality rates increased with night blindness (x 2.7), Bitot's spots (x 6.6) and both features(x 8.6) reflecting the severity of the underlying Vitamin A deficiency⁷.

• High dose oral Vitamin A supplementation for children with measles in developing countries and high measles immunisation coverage.
• Prophylactic oral Vitamin A (100, 000 IU for under 1 year olds and 200, 000 IU for 1-4 year olds) every 3-6 months in areas of high risk.