Q. What is CORNEA?
A. This is a piece of transparent tissue that fits like a watch crystal (outer glass cover of the watch) over the colored part of the eye called the iris. Unlike the crystal of the clock, which is flat, the cornea is dome-shaped. The light passes through the transparent cornea, as it would through a window, to the back of the eye. Parallel rays of light that pass through the cornea bend to focus on the retina, which is the inner lining of the back of the eye, like the film in the camera.
Q. How does the cornea become cloudy?
A. The cloudiness or irregularity of the cornea can be caused by many different types of problems. When the cornea becomes cloudy, similar to the frost of the glass, the light can not pass through the eye and the vision is deficient. Some of the causes are:
· Infection and injury to the eye.
· Nutritional disorders such as vitamin A deficiency
· Reaction to drugs, eg. Stevens-Johnson syndrome
· Degenerations and corneal dystrophies (hereditary conditions that can cause cornea fogging in adult life)
· Keratoconus (an irregularity of the shape of the cornea, where there is a progressive "cone" of the cornea) In this condition, although the cornea is clear, the quality of the vision gradually deteriorates. The cloudiness only occurs in the very late stages.
· Darkening of the cornea as a complication of cataract or glaucoma surgery
Q. In such cases, how is vision restored?
A. The only way to restore vision is to replace the cornea with healthy corneal tissue donated by a surgery called a corneal transplant or keratoplasty. This involves removing a central disc from the abnormal cornea and replacing it with a normal cornea piece of similar size obtained from a donor eye. The cornea is the only part of the eye that can be transplanted.
Q. How successful is corneal transplant surgery? Is it true that most corneal transplants become opaque in a few years?
A. The cornea transplant or the cornea graft, as it is also called, is devoid of blood vessels. Therefore, of all the transplants performed on the body, such as the heart, liver, kidney, etc., it has the least possibility of rejection. I modify the previous statement: it would be in second place in terms of success rates in hair transplants! Even if a rejection occurs, in most cases it can be successfully treated with eye drops without having to resort to systemic immunosuppressive medications, as is the case of transplants rejected in other parts of the body. I have seen several grafts made 30 and 40 years ago, remaining very clear until today! Grafts made in eyes where the cornea is already vascularized naturally, have a more unfavorable long-term prognosis (expected result, in simple terms). However, in the event that a graft fails or is rejected for some reason and the rejection is not reversed with timely treatment, everything is not lost. If the rest of the eye has no other complications, it is possible to perform a new graft, that is, one more graft (naturally after removing the anterior opaque graft) and restore vision once more.
Q. When does rejection usually occur?
A. From the statistical point of view, rejection occurs more frequently in the first year after transplantation and after any major or minor surgery in the eye, that is, a corneal graft patient who is now undergoing surgery of cataracts or even the removal of sutures from the cornea (commonly one year ago). or something like that after corneal graft surgery) has a higher risk of graft rejection in the month immediately after the surgical procedure.
Q. How does the patient know that there is an early rejection and that he should go to the nearest ophthalmologist?
A. If the patient suddenly experiences an increase in redness, pain, tearing of the operated eye or a fall in vision in the same eye, you should immediately consult your nearest ophthalmologist, preferably the same day. You should avoid the temptation to take telephone advice for your symptoms. This is because these same symptoms can occur in graft rejection, as well as in graft infection. The treatment for the first is the very frequent instillation of topical corticosteroid drops, while this will worsen the condition if it is a graft infection and not a rejection.
Q. Can all opaque corneas be successfully transplanted to restore vision?
A. I mentioned a few paragraphs ago that corneas that already have blood vessels growing in them have a more unfavorable prognosis (The meaning of the prognosis was also explained in a previous answer). In addition to these, eyes that have a history of rejected anterior grafts are at greater risk of developing rejection again, since the body now knows there is an intruder and sends its defense forces (white blood "killer" cells) to destroy the invader. In addition, eyes with inadequate tear secretion or poor quality tears are not good candidates for corneal grafting. Any condition that has destroyed the "limbus", that is, the factory that constantly replenishes the cells on the surface of the cornea, which is at the junction between the black and the white of the eye, makes a corneal transplant surgery be doomed to failure. Some of these conditions are chemical burns, reactions to medications such as Stevens Johnson syndrome, which destroy stem cells in the limbus and certain congenital conditions such as Aniridia, in which, to begin with, there is a very low share of stem cells. For more information on stem cells, read the chapter on "Eye Surface Disorders."
Q. What is the "new" development in corneal transplant surgery, the "lamellar" cornea transplant or keratoplasty?
A. Most cornea transplants performed in India and even around the world are "full thickness" corneal transplants (technically called penetrating keratoplasty). The diseased cornea is removed with all its layers and replaced by a donor cornea similar or slightly larger, also of "full" thickness. However, in certain diseases, such as "keratoconus" or corneal cornea or superficial corneal scars, the innermost lining of the cornea, called the endothelium, is intact and healthy and, therefore, it is not necessary to change it. In these cases, approximately 90% of the thickness is changed, that is, the innermost layer, the endothelium is left unchanged. Since the donor endothelium is primarily responsible for the rejection response of the patient's immune system, the chances of rejection of this "lamellar" graft are drastically reduced. However, this procedure requires a bit more skill than the usual penetrating keratoplasty and has a rate of operative complications (requiring conversion to penetrating keratoplasty) of approximately 5-10% in the best of hands. In addition, DALK (deep anterior lamellar keratoplasty, as it is also called) can not be used in patients with unhealthy endothelium. Therefore, it requires careful patient selection.
Q. I have heard about another procedure called "Endothelial keratoplasty". What is this?
A. I congratulate you on your listening skills. This procedure, which is even more demanding from the technical point of view than DALK, requires special instruments and has not yet been carried out routinely. This is the transplant of only the inner lining of the cornea, the endothelium, after removing the patient's own inner lining. It is also known as DSEK and DSAEK and posterior lamellar keratoplasty. You do not need to bother your head with the complete forms of these acronyms. You will probably forget them after reading them anyway. It can be done for those whose internal lining of the cornea is only dysfunctional and the rest of the cornea is fine. In general, sutures are not required in these cases, so visual recovery is much faster and suture-related complications are eliminated.
Q. Is there any hope of restoring vision for those unfortunate patients who can not receive or not a cornea transplant but have a diseased cornea?
A. Yes, they can be equipped with an artificial cornea or keratoprosthesis, so it is recommended to read the chapter dedicated especially to the subject.
Q. What are the expenses involved in the cornea transplant?
A. These vary considerably depending on the geographic region of the country where the surgery is performed. In many parts of India, these surgeries are performed only in government, municipal or trust hospitals where there are no charges or minimal cost. In larger cities, it is also done in the private sector. Although the eyeball is donated free of charge, most eye banks perform extensive tests on the donated tissue and analyze the donor's blood to detect AIDS, hepatitis and other communicable diseases. They also employ highly qualified personnel who evaluate the eyeball to decide the suitability of its use. All this costs money, which is charged by the eye bank as "processing charges". In Mumbai, for example, this cost is around Rs.6000 / per patient at the time of writing this edition. This charge only applies to private sector patients, who make up only 30% of all patients who receive donated corneas in Mumbai. The remaining 70% of the cornea is distributed practically at no cost to the municipal and free hospitals of Mumbai.
Q. What about the surgical fees?
A. These also vary from state to state. In states where corneal graft surgeries are performed in the private sector, the professional fees charged by an eye surgeon are generally what it would charge for modern cataract surgery.
Q. Is this morally justified? After all, you are receiving an eyeball donated by the deceased donor!
A. Morality is a relative issue. No surgeon charges for the eyeball or the cornea (however, eye banks may charge a processing fee – see previous answer). However, surgeons trained in corneal graft surgery have spent a lot of money to acquire this experience. In addition, they do need good surgical microscopes, disposable trephines and other expensive tools to perform good corneal graft surgery. Most cornea surgeons would like to do just one corneal surgery to make a living. However, as the availability of tissue is low, they end up doing cataracts and other surgeries to earn their daily bread. Virtually no eye surgeon in the private sector survives only on the proceeds of corneal transplant surgery. Most eye surgeons who perform a good number of transplants use the income of patients to subsidize surgery for those who can not afford them.
Q. Can a blind person recover his sight with an "eye transplant"?
A. No, the cornea graft or corneal transplant surgery can only benefit blind people because the cornea becomes opaque. The rest of the tissues of the eye can not be transplanted. As of today, retinal transplants are being tested experimentally, but it will take many years, in any case, before this procedure can be successfully performed to restore the vision of those with diseased retinas.
Q. Can a person who has received a corneal transplant donate their cornea after death?
A. yes If the cornea is clear, it can be reused to see another blind person more corneal. It would be a truly noble gesture!
Read the full article "Everything I wanted to know about corneal transplants" that Dr. Quresh Maskati wrote on Practo.com here: https://www.practo.com/healthfeed/everything-you-wanted-to-know -about -corneal-transplants-3208 / post
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