Keratomalacia

Synonym - Xerotic Keratitis

Xerophthalmia is the term used for deficient tear production leading to dry eye (particularly affecting the cornea) associated with vitamin A (retinol) deficiency. There may be insufficient absorbtion or poor metabolism of the vitamin. If left untreated, xerophthalmia progresses to keratomalacia: the cornea becomes thin and soft, eventually ulcerating. At worst, there may be perforation with secondary extrusion of the globe contents but other sequelae include corneal scarring, a permanent fibrotic deformity of the eye ball (phthisis bulbi) and blindness.

• It is the commonest cause of acquired paediatric blindness worldwide, accounting for 0.5 million cases worldwide.¹
• In western societies, it can occur among those with a poor nutritional status due to a variety of factors (see below).

Risk factors

• Primary vitamin A deficiency is prevalent in much of the developing world, particularly 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.
• It may be precipitated by a systemic illness such as measles ("measles blindness"),² pneumonia or diarrhoea.
• In the west, it is more likely to present in the context of alcoholism,³ severe mental illness⁴ or eating disorder⁵ or malabsorption of fat soluble vitamins (for example, cystic fibrosis, pancreatic disorders, inflammatory bowel disease, liver disease, intestinal bypass surgery).
• Old age can also put people at greater risk of vitamin A deficiency.⁶

• Night blindness (nyctalopia or poor dark adaptation) tends to be the earliest ocular symptom of Vitamin A deficiency.
• Eyes become dry (cornea, lacrimal glands and conjunctiva all affected), known as xerosis.
• Keratomalacia presents with bilateral central grey, indolent corneal ulcers surrounded by a dull, hazy cornea, sometimes with photophobia.
• The cornea becomes soft and necrotic, usually progressing to perforation.
• Bitot's spots⁷ are areas of abnormal squamous cell proliferation and keratinisation of the conjunctiva which look like foamy, wedge-shaped areas in the conjunctiva. They are usually temporal 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.

Addressing the ocular problems

• Treatment will be on the aggressive end of the treatment spectrum of dry eye with intensive lubrication ± a bandage contact lens, depending on how far the condition has progressed.
• Topical antibiotics will be required to prevent secondary keratitis.
• Once the acute situation has settled, there will inevitably be some degree of corneal scarring. Depending on the extent and the individual's circumstances, keratoplasty may be considered. Success of this procedure for this condition has been limited⁸ but there are occasional case studies suggesting that this line of treatment may have a future as techniques improve.⁹

Addressing the systemic problems

• Dietary issues need to be formally assessed by a dietician who can advise on a vitamin A and protein-rich diet. (Some high risk individuals may benefit from vitamin A or beta carotene supplements but this should be avoided in pregnant women where there is a risk of vitamin A embryopathy).
• Underlying problems need to be addressed e.g. alcohol abuse, eating disorder, inflammatory bowel disease.

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 deficiency.¹⁰

• 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.