Corneal Blindness – The 4th Most Common Cause of Vision Loss
Corneal blindness has a considerable health and economic burden on the community and the state exchequer especially since it affects the relatively younger population which is generally economically productive.
Unlike cataract, glaucoma and Age-Related Macular Degeneration, corneal blindness affects youth, mainly from rural areas, and especially those from a lower socio-economic background, who anyway have inadequate access to healthcare. By and large, in low and middle-income groups, infections and trauma remain the most important causes, followed by poor access to proper eye care.
Also, management of corneal blindness requires a corneal transplant, a surgery that is complex and dependent on cadaveric corneal donations and needs tremendous post-operative care and follow-up. It makes corneal blindness a unique challenge for the eye care provider.
What is the cornea?
The cornea is the outermost layer of the eye, which is clear and dome-shaped. The black part of the eye, the iris, if you observe, is covered by the transparent, dome-shaped cornea. The cornea, along with the natural lens of the eye is responsible for focusing the rays of light entering the eye, on to the retina, the light-sensitive portion of the eye.
For the cornea to function correctly, it must remain transparent and free from any surface irregularities. In scarring, which can be due to infections, inflammations, trauma, or hereditary diseases of the cornea, can result in severe loss of vision and even corneal blindness.
What is corneal blindness?
Any profound decrease in vision or blindness due to diseases of the cornea is termed corneal blindness. It is the 4th most common cause of blindness all over the world, accounting for over 5% of the total blind population. The other leading causes include cataract, glaucoma, and age-related macular degeneration.
What are the causes of corneal blindness?
- Infections and Ulcerations: Bacterial, fungal, or viral keratitis or infection of the cornea due to various microbes are the most important causes. Trachoma, an eye infection, is the leading cause of corneal scarring and has blinded as many as9 million people worldwide. Relatively rare infections like onchocerciasis and leprosy have resulted in 2.5 Lakh cases of blindness.
- Malnutrition: Vitamin A deficiency is also an important reason for childhood blindness, affecting children with malnutrition and failure to thrive.
- Trauma: Eye trauma and corneal ulcerations are the second most important disease burden, resulting in 2.0 million new cases of blindness each year.
- Congenital Diseases: Also, each year 3.5 Lakh children are affected by blindness, either due to a congenital disorder (born blind) or due to corneal infections and ulcerations in early infancy.
- Other Corneal Disorders: Certain hereditary and acquired disorders like Fuch’s Endothelial Dystrophy, Pseudophakic bullous Keratopathy, and other corneal degenerations and dystrophies can also cause a profound loss of vision.
- Lifestyle Issues: An essential consideration in this regard, especially in a developing country like India, with a rich system of traditional medicine or home remedies, is the fact that several ayurvedic drops, kajal, and surma have been traditionally used which may cause more harm than good, resulting in loss of vision. Traditional practices of using honey as an eye drop and ginger juice for eye cleansing are potentially disastrous, as is the indiscriminate use and dispensing of steroid eye drops by chemists and quacks.
What are the measures for prevention of corneal blindness?
The approach to managing corneal blindness is three-pronged: prevention, treatment, and rehabilitation.
- Provision of Clean Water: Trachoma is caused by Chlamydia trachomatis, which causes corneal blindness due to lid distortions are known as entropion and trichiasis and due to an increased probability of infections and ulcerations. Trachoma is transmitted due to poor facial and hand hygiene. In fact, since the improvement in water supply facilitates facial cleanliness, it is one of the four components of the SAFE strategy for trachoma control. The SAFE Strategy has four elements, and each one of them is as important. These include Surgery for trichiasis, Antibiotics for infection, Facial cleanliness and Environmental improvement to control transmission.
- Xerophthalmia: Xerophthalmia or eye dryness is caused by vitamin A deficiency and which can be aggravated by measles, or diarrhea or any debilitating disease in the young, malnourished population. Vitamin A deficiency is responsible for more than fifty percent of the new cases of childhood blindness each year. For prevention of vitamin A deficiency, the strategy involves Vitamin A supplementation, measles vaccination, and nutritional advice, in addition to ensuring early treatment of diarrhea.
- Onchocerciasis (River Blindness): It is caused due to an inflammation of the eye in response to the microfilaria of Onchocerca volvulus which migrates deep inside the eye, into the cornea and the retina. This results in a profound inflammatory reaction, and consequent blindness. This infection is transmitted by the Simulium fly and control measures involve promotion of hygiene, measures to control the Simulium fly and mass distribution of ivermectin, the definitive treatment for onchocerciasis.
- Trauma: Corneal injuries, especially with vegetable matter, are prevalent in the farming community, and in children. Even small corneal abrasions, if not treated properly can result in profound vision loss. Simple antibiotic eye drops, if used correctly, can help prevent a corneal infection following trauma. However, most of rural India lack access to proper healthcare facilities and is at the mercy of quacks and indigenous methods of treating injuries, which can often be detrimental to eye health.
What is the definitive cure?
Definitive treatment of corneal blindness is corneal transplantation or corneal graft. In this surgery, either part or the entire cornea is replaced by one which has been donated upon death by another person. The reason for the inordinate number of people still awaiting corneal transplants is that the number of eyes donated each year are far less than those required for the existing people with corneal blindness. Also, fresh cases of corneal blindness keep getting added, swelling the numbers on the transplant list.
The most important directive for decreasing corneal blindness, therefore, is two-fold: promoting eye donation and transplantation, while at the same time, preventing corneal blindness by improving awareness about eye diseases and promoting timely interventions.
Kindly read more about diseases and treatments related to cornea at Eye7 at this link.