Corneal disease remains major cause of blindness

Washington, DC-Corneal pathology continues to be a major cause of blindness in developing countries of the world, and nearly all of the diseases and conditions leading to corneal blindness are preventable or treatable with existing knowledge and technology, said Gullapalli N. Rao, MD, at World Cornea Congress V.

At least 80% to 90% of all corneal blindness in the world could be prevented thanks to the SAFE-surgery, antibiotics, facial cleanliness, environmental improvement-strategy for trachoma; vitamin A supplementation; universal measles vaccination; prompt, appropriate trauma management; and quality ophthalmic care, Dr. Rao said. He is a distinguished chairman of eye health, L.V. Prasad Eye Institute, Hyderabad, India, as well as chairman of the board of trustees, and president, International Agency to Prevent Blindness.

Dr. Rao said the major causes of corneal blindness fall into two categories-those contributing to unilateral blindness and those resulting in loss of sight in both eyes. The most common causes of unilateral corneal blindness can be categorized as infection, injury, and iatrogenic. Conditions that fall within the bilateral classification include trachoma, vitamin A deficiency, measles, onchoceriasis, leprosy, ophthalmia neonatorum, and dystrophies.

He noted that trachoma, vitamin A deficiency, and onchoceriasis provide excellent examples of the positive impact derived from public-private partnering to improve public health. Major pharmaceutical corporations have been donating the drugs needed to eliminate each of those problems, and the collaboration between the government and the private sector has made a major difference in controlling these diseases, Dr. Rao explained.

As a result, statistics from the World Health Organization show there have been significant decreases in the number of people blind who are blind from trachoma as well as definite evidence of a decline in the number of people losing their sight due to onchoceriasis.

"This is excellent news," he said.

Data from limited epidemiologic studies on causes of blindness and from studies analyzing indications for corneal transplantation procedures highlight the magnitude of the problem of corneal blindness in developing countries and the striking geographic differences.

In one investigation examining the anatomic causes of blindness among children in schools for the blind, corneal blindness was a leading cause of blindness in India, other Asian countries, and in sub-Saharan Africa. Corneal blindness accounted for 23% to 31% of cases of blindness in those areas.

Corneal disease examined In a population-based study undertaken by Dr. Rao and colleagues examining causes of blindness in the Indian state of Andra Pradesh, corneal disease was the fifth most prevalent cause of blindness and accounted for 7.1% of blindness overall. Examining the types of disorders within the category of corneal disease pointed to vitamin A deficiency as a common underlying problem. Extrapolating their data to the whole population of India, Dr. Rao et al. estimated there would be 1.3 million Indian people blind bilaterally because of corneal disease.

In another population-based study of more than 4,000 adults of 50 years of age and older in Rajasthan, a remote area in northwest India, corneal disease was the second most common cause of blindness after cataract, and most types of corneal disease were preventable or treatable, Dr. Rao said.

Data from studies of indications for corneal transplantation show that in America and western European countries, the leading diagnoses for that procedure are pseudophakic bullous keratopathy, Fuchs' dystrophy, keratoconus, and graft failure.

In contrast, corneal scarring subsequent to infectious disease is the major indication for corneal transplantation in India.

"Pseudophakic bullous keratopathy, keratoconus, and Fuchs' dystrophy constitute the so-called excellent prognosis group for penetrating keratoplasty, where-as . . . the leading reasons for corneal transplantation in developing countries are associated with a poor prognosis," Dr. Rao said.

He said that when corneal opacity occurs and mandates penetrating keratoplasty for visual rehabilitation, there are also geographic differences in the requisites for success of the transplantation surgery that place developing countries at a disadvantage.