Sunday, February 3, 2008

7.16 Organ donors

(A post-op transplanted cornea - the zig-zag lines are the sutures)

Organ donation remains a voluntary act, at least in the US. The way it must be. Usually, at driver's license renewal, a question on whether you are willing to donate your organs is put forth. You can answer either yes or no and your wish is honored. Or you can carry a donor card with you (see picture below). In the hospitals, it is often a difficult task for physicians to request organ donation of a deceased from the grieving family; although who almost always give their consents.
Organ donation actually cuts through social, cultural and religious boundaries. It is a universal human act of giving and care.

Donated organs that can benefit many others include: Kidneys, heart, liver, pancreas, intestines, lungs; skin; bone and bone marrow; and the cornea. To keep these organs/tissues safe, both the FDA and the Health Resources and Services Administration (part of the HHS) have issued rules and guidelines - necessary for avoiding life-threatening infectious agents. Unfortunately, there are also unscrupulous operators who provide contaminated or cancerous organs that result in the death/injury of the recipients.

Here, we will touch upon the corneal issue. You can elect to donate only your corneas (see donor card above). They are a true gift of sight. The Sri Lanka Eye Donation Society is known to have collected tens of thousands of corneas, made available not only to Sri Lankans but also to numerous patients in other countries. These and all other donors deserve our special gratitude and respect.

It is estimated that in the US, between 30-50,000 corneal transplants are performed each year. And the reason for such an operation is to restore vision to patients with the following problems:

Keratoconus (cone-shaped cornea, see illustration below) and thinning of the cornea
Cornea scarring and ulcers (caused by, e.g., infection or injury)
Corneal opacities or severe edema

(Keratoconus - from
Eye banks are now responsible for retrieving and preserving the donor eyes which are then provided to corneal surgeons. Since the eyes have limited "shelf life", unused (plus those deemed unsuitable) eyes can also be used for lab research. Essentially, there is no such thing as a wasted donor eye.

So can the donor corneas be preserved for as long as possible without losing their viability? In the olden days, the whole eyes were simply stored in a refrigerator and the corneas used within 2 days. Now, the excised corneas are placed in culture media such as Optisol GS or Eusol-C, which can preserve the cornea for up to 2 weeks (at 0-4°C). Other MEM-based modified culture media may also be used if needed. The corneas are inspected for the shape and count of the endothelial cells. The more cell loss the less viable/successful after transplantation.

Technically, there are three corneal transplant procedures. The most common is Penetrating Keratoplasty, in which the whole damaged cornea is replaced with the donor cornea. A trephine (similar to a miniature cookie cutter) is used to cut the donor and recipient corneal buttons, so the sizes match. Unexpectedly, the recent popularity of LASIK has actually reduced the donor cornea availability because the cornea now maybe too thin for penetrating keratoplasty. The alternative is to use only the endothelium, which is untouched by the LASIK procedure, for Deep Lamellar Transplant. Yet another procedure is the Surface Lamellar Transplant, in which, only the superficial layers of the cornea, in toto, are replaced. The corneal surgeon of course is the one who can decide which procedure works the best for you.

Corneal transplants have the usual surgical complications such as infection, bleeding, inflammation, and the occasional rejection (rare because the cornea is not a vascularized tissue). However, the success rate is quite high, e.g., 98% in keratoconus repair and more than 90% overall. We have just seen a case of of keratoconus that recurred after the transplant. This has been reported by others, in 11.7% of post-op cases. The causative factor is, however, still unknown.

By and large, corneal transplant, as cataract extraction, is a very safe way of replacing damaged corneas.

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