Corneal blindness accounts for 0.52% of total blindness in the Indian subcontinent. The cornea can be the site of various disorders. However before discussing the common problems, which can affect the cornea, it is important to understand the structure and function of the normal eye.

The eyeball is made up of three "coats". The sclera ('white of the eye') is the protective outer coat of the eye, the front portion of which is transparent and is called the cornea. The innermost lining or coat of the eyeball is the retina, a thin light-sensitive film. Between the sclera and the retina lies the choroid, which has a chiefly nutritive function. Some distance behind the cornea is the iris, which is visible as the 'colored portion of the eye' with a central opening - the pupil. This is just like the shutter or diaphragm aperture of the camera and helps regulate the amount of light entering the eye. Behind the iris lies the transparent lens, which helps in focusing light on the retina. The space between the lens and the retina is filled with a clear jelly called the vitreous body.

The eye is like a camera in which lenses focus the picture on a light sensitive film. In the human eye, the transparent cornea and lens focus light on the retina, which changes it into electrical signals, which are then transmitted to the brain by the optic nerve to be perceived as images.

A corneal transplantation, like a cataract operation, is usually performed under local anesthesia. General anesthesia is used for children and apprehensive or nervous patients. The operation is completely painless and takes about one hour to perform. The diseased, cloudy, opaque cornea is removed from the recipient's (living patient's) eye, and re placed by a new clear cornea (graft) from the donor's (deceased person's) eye. The new cornea is then sutured or stitched into place. As few as eight and as many as 20 or more sutures may be used, according to the size of the graft, to hold the border of the graft to the border of the recipient. If the operation is successful and the graft "takes" and remains clear, the patient should see well again, provided the lens and the retina behind the cloudy cornea are normal.

The patient is usually hospitalized for one day but requires rest for the next one month although returning to light work is not a problem. However frequent follow-ups are required over the following six months to one year.

In favorable subjects the rate of success of corneal transplantation may be as high as 60%, with good final visual acuity with glasses. In unfavorable subjects, the rate of success may be around 10 to 20%. Each patient is evaluated individually before definite results can be predicted.

The most important factors in determining the final results are:

	Basic corneal disease (some types of corneal disease respond better to corneal transplantation than others).
	State of the donor's cornea.
	Surgical technique and skill.
	Healing ability of the recipient cornea.
	Sensitivity reactions between donor and recipient cornea.

A corneal transplantation will not help every blind person to see again. If a person is blinded by glaucoma, a detached retina, or degenerative change and the retina has been damaged or destroyed, nothing can restore lost sight. Corneal transplantation restores vision only in eyes that have been partially blinded by corneal disease. Some vision must be present before transplantation is even contemplated.

THE OCCURRENCE OF PAIN, REDNESS, WATERING, LIGHT-SENSITIVITY AND DIMINISHED VISION, ANY TIME (EVEN MONTHS OR YEARS) AFTER CORNEAL TRANSPLANTATION SURGERY, REQUIRES IMMEDIATE ATTENTION OF YOUR OPHTHALMOLOGIST.