Keratomalacia is a progressive eye disease affecting the cornea, the transparent outer layer of the eye. This condition is a medical emergency because it can advance rapidly, causing the cornea to deteriorate and cloud over. If not addressed immediately, this can lead to irreversible blindness and typically affects both eyes.
The Role of Vitamin A Deficiency
Keratomalacia is the most severe stage of xerophthalmia, a condition caused by a profound lack of vitamin A. This vitamin is necessary for maintaining the health of epithelial tissues in the cornea and the conjunctiva, the membrane covering the white of the eye. Without sufficient vitamin A, these surfaces cannot function correctly, leading to the structural failures seen in the disease.
The underlying vitamin A deficiency is either primary or secondary. Primary deficiency, the most common cause, results from an inadequate dietary intake of foods rich in vitamin A, such as liver, eggs, and orange-colored fruits and vegetables. This is prevalent in regions where staple foods, like rice, lack beta-carotene.
A secondary deficiency occurs when the body is unable to properly absorb, store, or transport vitamin A, even with sufficient dietary intake. This can result from medical conditions that interfere with fat absorption, including cystic fibrosis, celiac disease, and Crohn’s disease. Liver disorders can also contribute, as the liver is the primary storage site for vitamin A.
Signs and Progression of Symptoms
The progression of keratomalacia begins with the early stages of xerophthalmia. One of the first symptoms is night blindness (nyctalopia), a difficulty seeing in dim light. This occurs because vitamin A is a component of rhodopsin, the pigment in the retina responsible for low-light vision.
As the deficiency continues, the eyes become excessively dry, a condition known as xerosis. The conjunctiva starts to appear dull and dry, and distinctive foamy patches called Bitot’s spots may form on the whites of the eyes. These spots are accumulations of keratinized epithelial cells and are a sign of long-standing vitamin A deficiency.
The disease then advances to affect the cornea, causing corneal xerosis where the surface becomes hazy and dry. In this advanced phase, the corneal tissue begins to soften and can develop ulcers. This process, described as liquefactive necrosis or “melting,” can rapidly destroy the cornea, leading to perforation and permanent blindness.
Diagnosis and Medical Intervention
The diagnosis of keratomalacia is based on a clinical eye examination and a patient’s history, particularly in areas where malnutrition is common. An ophthalmologist will look for signs such as a hazy, dry, or ulcerated cornea. In some cases, a trial of vitamin A therapy may be used to confirm the diagnosis.
To confirm the deficiency, blood tests can measure serum retinol levels. Levels below 10 mcg/dL are associated with ocular symptoms. However, serum levels may appear normal in the early stages because the body will drain vitamin A from liver stores to maintain circulating levels.
Because keratomalacia is a medical emergency, intervention is immediate. The primary treatment involves high doses of vitamin A, given orally or by injection, to rapidly correct the deficiency. Antibiotic eye drops or ointments are also prescribed to prevent or treat secondary bacterial infections that can occur once the protective barrier of the cornea is compromised by ulceration.
Prevention and Long-Term Management
Preventing keratomalacia is centered on ensuring adequate vitamin A intake. Public health strategies in high-risk areas include food fortification and distributing high-dose vitamin A supplements, particularly for young children and pregnant women. Educating communities on the importance of a balanced diet is also a preventive measure. Good dietary sources include:
- Leafy green vegetables
- Carrots
- Sweet potatoes
- Mangoes
- Animal products like liver
- Eggs
For individuals with existing corneal damage, long-term management focuses on the consequences. Significant corneal scarring can permanently impair vision. In severe cases, a corneal transplant (keratoplasty) may be a surgical option to replace the damaged tissue and restore some sight. However, the visual outcome can be poor even with surgery.