It is an eye disorder that results from vitamin A deficiency.
Vitamin A is necessary to maintain specialized epithelia (as in the cornea and conjunctiva).
The precise mechanism is not yet known, but vitamin A is necessary for the maintenance of the specialized epithelial surfaces of the body.
Lack of vitamin A causes atrophic changes in the normal mucosal surface, with loss of goblet cells and replacement of normal epithelium by inappropriate keratinized stratified squamous epithelium.
In addition, the cornea’s own substance breaks down and liquefies, causing keratomalacia.
The resulting cornea becomes totally opaque, which is one of the most common reasons for blindness around the world, especially in developing countries.
Keratomalacia is an eye condition in which the cornea, the clear front part of the eye, becomes cloudy and softened. This eye disease often begins as xerophthalmia, which is severe dryness of the cornea and conjunctiva.
The conjunctiva is the thin mucous membrane that lines the inside of your eyelid and covers the front of your eyeball.
Once the conjunctiva dries, it thickens, wrinkles, and becomes cloudy, while the cornea (the clear layer that forms the front of the eyeball) softens.
If keratomalacia is not treated, the softening of your corneas can lead to infection, rupture, and tissue changes that can lead to blindness. Keratomalacia is also known as xerotic keratitis and corneal fusion.
What Causes Keratomalacia?
The human body stores vitamin A mainly in the liver. Vitamin A plays a major role in the reconstitution of a visual pigment (rhodopsin) within the retinal rods that is required for night vision.
It is also essential for the formation and maturation of epithelial cells and the proper development of bones and teeth.
Sources of vitamin A in the diet include oils from fish liver, liver, whole cow’s milk, other dairy products (eg, butter, cheese), egg yolks, green leafy vegetables, and yellow vegetables and fruits.
Keratomalacia is caused by severe vitamin A deficiency in patients with protein-calorie malnutrition.
There is no medical consensus as to whether vitamin A deficiency is due to a deficiency in the diet or a metabolic inability to absorb the vitamin.
Keratomalacia usually affects both eyes and is found more frequently in developing countries where the population has a low dietary intake of vitamin A, or a deficiency in protein and calories.
Primary vitamin A deficiency is common in certain regions where rice is a major component of the diet (eg, East and South Asia); rice does not contain beta-carotene, which the body converts into vitamin A.
It is characterized by a hazy and dry cornea. Corneal ulceration with secondary infection is common. The lacrimal glands and conjunctiva are also affected.
The lack of tears causes extreme dryness of the eyes and foamy spots appear on the temporal bulbar conjunctiva and often nasal (Bitot’s spots). Night blindness can occur.
Additionally, keratomalacia is common with certain malnutrition disorders that result from insufficient protein and energy intake (i.e., protein-calorie malnutrition, such as kwashiorkor).
In such cases, vitamin A deficiency can be the result of dietary deprivation and faulty storage and transportation of vitamin A.
Babies and children who are allergic to milk or who receive diluted formula may also be at risk for vitamin A deficiency and associated keratomalacia. Whole cow’s milk and human milk are adequate sources of vitamin A.
Vitamin A deficiency and keratomalacia can also be secondary to certain diseases or conditions characterized by insufficient conversion of beta-carotene to vitamin A or impaired storage, absorption, or transport of vitamin A (secondary vitamin A deficiency).
For example, impaired vitamin A absorption or storage may occur from chronic intestinal disorders, such as:
- Ulcerative colitis; Sprue or celiac disease; cystic fibrosis or other disorders characterized by pancreatic insufficiency and associated malabsorption; or bowel bypass surgery (duodenal bypass).
Poor storage or absorption of vitamin A can also be associated with:
- Infection of the small intestine (giardiasis); partial obstruction of the small intestine at birth; obstruction of the bile ducts; or liver disease, such as internal scarring and impaired liver function (cirrhosis).
Keratomalacia occurs more frequently in developing countries due to prolonged dietary deprivation of vitamin A or protein-calorie malnutrition.
As noted above, keratomalacia is a major cause of blindness in young children in these areas. In developed countries, vitamin A deficiency occurs most frequently when there is interference with the intake, absorption, or transport of vitamin A.
What are the symptoms?
Keratomalacia is an eye condition characterized by distinctive eye changes due to a severe vitamin A deficiency.
In some affected people, the additional effects may be the result of vitamin A deficiency, the severity of which tends to be inversely related to age.
Symptoms of keratomalacia include:
- Night blindness, or trouble adjusting your vision in dim or dark light.
- Extreme dryness of the eyes.
- Cloudiness in your corneas.
Keratomalacia is often preceded by an episode of infection – diarrhea and respiratory infection are common triggers.
Prospective studies also show that common childhood infections, including diarrhea, respiratory diseases, measles, and chickenpox, induce hypovitaminosis A.
During acute infection, not only food intake is reduced, but metabolic disturbances are also known. These include decreased absorption of vitamin A, impaired retinol transport, and increased renal excretion.
The slow normalization of these mechanisms together with a low dietary intake of vitamin A during the acute phase and recovery lead to a ventricular assist device (VAD).
Parasitic infections such as ascariasis and giardiasis also aggravate the ventricular assist device.
Intestinal worms can compete directly for vitamin A absorption, in addition to its more general impact on health by suppressing appetite.
Initial ocular findings commonly include poor fit of the eyes to vision in the dark or dim light (altered dark adaptation) and associated night blindness due to retinal dysfunction.
The retina is the light-sensitive membrane on which images are focused at the back of the eye. It contains specialized nerve cells (photoreceptors) that convert light into nerve impulses.
Photoreceptors include “rods” that are sensitive to low intensity light and therefore require night vision and “cones” that respond to high intensity light and colors.
“Dark adaptation” is the normal increase in the sensitivity of the rods to detect the light available for vision in dark or low-light areas.
Vitamin A deficiency leads to abnormalities in the structure and function of certain cells that line the surface of the eyes (i.e. epithelial cells).
Due to such epithelial changes and inadequate tear production, affected individuals develop:
Extreme dryness of the delicate membranes (i.e. conjunctiva) that cover the whites of the eyes and the inner lining of the eyelids (xerosis conjunctiva) and corneas (xerosis corneae).
The cornea is the transparent, thin-walled, “dome-shaped” region that forms the front of the eyeball; It serves as a protective covering and helps focus or bend (refract) light waves on the retina at the back of the eye.
Due to abnormal dryness of the conjunctiva and corneas (ie a condition known as ‘xerophthalmia’), there is unusual thickening and wrinkling of the conjunctiva, as well as increased cloudiness, dullness, wrinkles, and softening of the corneas.
In addition, in advanced vitamin A deficiency, silver-gray foamy patches (Bitot points) appear consisting of abnormal deposits of epithelial debris and secretions in the conjunctiva.
Evidence suggests that Bitot’s spots are more likely to develop in young children with other manifestations of vitamin A deficiency.
Without proper treatment, increased softening of all or part of the corneas (keratomalacia) can lead to chronic infection, ulceration and rupture (perforation) of the corneas, and degenerative tissue changes (such as corneal protrusion and ocular reduction [ phthisis bulbi]), resulting in blindness.
As noted above, in some affected individuals, vitamin A deficiency can have additional effects. For example, mental and physical growth retardation is a common sign in children.
Vitamin A deficiency can also be associated with:
Dryness and peeling of the skin; decreased levels of the oxygen-carrying component of red blood cells (anemia); abnormal enlargement of the liver and spleen (hepatosplenomegaly).
A greater susceptibility to certain infections, as for example, due to epithelial changes of the digestive, respiratory and urinary tracts; and / or other findings.
Evidence suggests that children with vitamin A deficiency are particularly susceptible to possible complications associated with measles.
How is it diagnosed?
Keratomalacia can be diagnosed based on a complete history of the patient; full clinical evaluation; blood studies (for example, evaluation of beta-carotene and vitamin A levels); and additional specialized tests.
The eye exam should include:
- Evaluation of the external appearance of the eyes, visual acuity, eye movements and visual fields; the use of a lighted microscope to view the conjunctiva, corneas, and other regions of the eyes (slit lamp examination).
- Dark adaptation measures to help detect night blindness; and / or additional diagnostic evaluations (for example, to exclude other possible causes of night blindness).
In addition, the evaluation may include a microscopic examination of superficial cell scrapings from the eyes.
In some cases, other diagnostic studies may also be performed to help exclude or confirm possible secondary causes of vitamin A deficiency and keratomalacia.
Furthermore, in some cases, a trial with appropriate therapeutic doses of vitamin A can confirm a diagnosis.
Electroretinography, a test that looks at light-sensitive cells in the eye, can also be used to diagnose keratomalacia.
Along with increasing vitamin A intake, people suffering from keratomalacia are usually prescribed lubricating eye drops or ointments and antibiotics.
In cases where the cornea has been sufficiently damaged, keratoplasty is recommended. Keratoplasty is a surgical corneal transplant to replace scar tissue that restricts vision.
Treatment of vitamin A deficiency and associated keratomalacia includes vitamin A supplementation, with dose levels and duration of treatment determined by the severity of the deficiency and other factors.
However, prolonged daily administration of high doses should be avoided, particularly for infants, as it can result in toxicity (i.e., hypervitaminosis A).
In infants and young children, manifestations of acute vitamin A toxicity due to large doses may include increased intracranial pressure, drowsiness, nausea, vomiting, and other abnormalities.
Chronic hypervitaminosis A, which can be the result of excessive doses over several weeks or months, can be characterized by:
Irritability, poor appetite, dry, itchy skin, hair loss, chapped lips, general weakness, swelling of the bones, increased intracranial pressure, enlarged liver, and other abnormalities.
Also, because vitamin A can cause birth defects if given in high doses during pregnancy, extreme caution should be used when treating women in their childbearing years.
Experts recommend that doses of vitamin A do not exceed twice the recommended daily allowance for women who are pregnant or breastfeeding (ie, lactating).
Furthermore, in cases where keratomalacia occurs secondary to impaired vitamin A absorption, storage, or transport, treatment also includes appropriate therapeutic measures to help control or correct the underlying disorder or condition.
In some cases, the treatment of keratomalacia may include the administration of antibiotic drops or ointments to treat secondary infections, the use of other suitable eye drops, and / or additional measures.
Another treatment for this disorder is symptomatic and supportive.
What is the difference between keratomalacia and xerophthalmia?
Keratomalacia is a progressive disease that begins as xerophthalmia. Caused by a vitamin A deficiency, xerophthalmia is an eye disease that, if left untreated, can progress to keratomalacia.
It is characterized by abnormal dryness of the eyes. The condition begins with dryness of the conjunctiva, also known as conjunctival xerosis.
It then progresses to corneal dryness or corneal xerosis. In its later stages, xerophthalmia develops into keratomalacia.
Who is at risk for keratomalacia?
Those at risk of developing keratomalacia can be divided into two main groups: people who do not get enough vitamin A in their diet, and people who cannot absorb vitamin A.
People who consume low amounts of vitamin A:
- Babies and young children living in poverty.
- People, especially children, who are malnourished.
- People, especially children, living in developing countries.
People who have trouble absorbing vitamin A:
- People who abuse alcohol.
- People with inflammatory bowel diseases (IBD).
- People with liver disease.
- People with cystic fibrosis.
If you have a risk factor, it doesn’t mean you have or develop keratomalacia. However, it is a good idea to talk to your doctor about conditions in which you are in a risk group.
Measures to prevent vitamin A deficiency and keratomalacia include ensuring adequate nutrition through a balanced diet containing adequate protein and vitamin A or carotenes.
In some cases, routine preventive (prophylactic) vitamin A supplementation may also be required, such as for people with impaired vitamin A absorption, storage, or transport.
In developing countries where keratomalacia is a major cause of blindness, regular prophylactic vitamin A supplementation is recommended in children at appropriate doses, as determined by age and other factors.
Also, babies who are allergic to milk should receive adequate vitamin A in replacement formulas.
Parents should speak with pediatricians about the proper steps to ensure that their children receive sufficient levels of vitamin A and other necessary nutrients from their diets.
Experts also advise the administration of appropriate doses of vitamin A for children who are at risk for vitamin A deficiency and who develop certain viral infections, such as measles.
What is the perspective?
Keratomalacia is not common in developed countries, such as the United States and Great Britain, where diets generally include foods rich in vitamin A.
However, if you are in a high-risk group, have extremely dry eyes, or have trouble adjusting your vision in low light, consider calling your doctor for a consultation.
It may not be an early stage keratomalacia, but noticeable physical changes are worth bringing to your doctor’s attention.