Q. How does the patient know that there is early rejection and he should rush to the nearest eye doctor?
A. If the patient suddenly experiences increase in redness, pain, watering of the operated eye or a drop in vision in the same eye, he should immediately see his nearest eye doctor, preferably on the same day. He should avoid the temptation of taking telephonic advice for his symptoms. This is because these same symptoms can occur in graft rejection as well as in graft infection. The treatment for the former is very frequent instillation of topical corticosteroid drops while this will make the condition worse if it is a graft infection and not a rejection.
Q. Can all opaque corneas be successfully transplanted to restore vision?
A. I did mention a few paragraphs ago that those corneas already having blood vessels growing into them have a poorer prognosis. (Meaning of Prognosis also explained in a previous answer). Besides these, eyes which have a history of previous grafts rejected are more at risk to develop rejection again as the body now knows that there is an intruder and sends its defence forces (white blood ‘killer’ cells) to destroy the invader! Besides, eyes with an inadequate tear secretion or with poor quality tears are not good candidates for corneal grafting. Any condition that has destroyed the “limbus” i.e. the factory that constantly replenishes the cells on the surface of the cornea, which is situated at the junction between the black and the white of the eye, makes a corneal transplant surgery doomed to failure. Some of these conditions are chemical burn injuries, drug reactions such as Stevens Johnson syndrome, which destroy the stem cells at the limbus and certain congenital conditions such as Aniridia in which there is a very poor quota of stem cells to begin with. For more information on stem cells, read the chapter on “Ocular Surface disorders”.
Q. What is the ‘new’ development in cornea transplant surgery – the ‘lamellar’ corneal transplant or keratoplasty?
A. Most corneal transplants done in India and even the world over are ‘full thickness’ corneal transplants (technically called penetrating keratoplasty). The diseased cornea is removed with all its layers and replaced by a similar or slightly larger sized, donor cornea also of ‘full’ thickness. However, in certain diseases, such as ‘Keratoconus’ or conical cornea or in superficial corneal scars, the innermost lining of the cornea, called the endothelium is intact and healthy and therefore need not be changed. In these cases, approximately 90% of the thickness is changed, i.e. the innermost layer, the endothelium is left unchanged. Since it is the donor endothelium which is chiefly responsible for the rejection response by the patient’s immune system, the chances of rejection of this ‘lamellar’ graft are reduced dramatically. However, this procedure requires a little more skill than the usual penetrating keratoplasty and has a rate of operative complications (necessitating conversion to penetrating keratoplasty) of about 5-10% in the best of hands. Also, DALK (deep anterior lamellar keratoplasty as it is also called) cannot be used in patients who have unhealthy endothelium. It therefore requires careful patient selection.
Q. I have heard of another procedure called “Endothelial Keratoplasty”. What is this?
A. I congratulate you for your hearing abilities. This procedure, which is even more technically demanding than DALK, requires special instruments and is still not routinely done. This is transplantation of only the inner lining of the cornea –the endothelium, after stripping off the patient’s own inner lining. It is also known as DSEK and DSAEK and posterior lamellar keratoplasty. You need not bother your head with the full forms of these acronyms. You probably will forget them after reading them anyway. It can be done for those whose corneal inner lining only is dysfunctional and the rest of the cornea is OK. Sutures are generally not required in such cases, so visual recovery is much faster and suture related complications are eliminated.