HEALTHWATCH
No sutures in the eye
DR. SRINIVAS K. RAO, DR. SUJATHA MOHAN, DR. MOHAN RAJAN
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A look at the changing face of corneal transplants.
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BETTER VISION: After the conventional corneal replacement
OF the five senses, sight is considered the most important by most, as it allows one to perceive the wonders of the world. Of the many parts of the eye required for clear vision, the cornea — a delicate structure in the front — is literally our "window to the world".
To keep this delicate structure clear, a layer of cells on the back of the cornea, the endothelium, work as tiny "pumps" to constantly remove fluid from the corneal layers and keep it transparent. If these cells are damaged due to disease or other causes, the pump function fails and fluid accumulates in the corneal layers. Then the patient ceases to have clear vision.
Conventional procedure
Conventionally, a corneal replacement procedure is performed to help such unfortunate patients see again. Despite its success, routine corneal transplantation does suffer from a few drawbacks.
During surgery, a circular central disc of the affected cornea is excised and is replaced by a similar disc of healthy tissue from a donor eye.
To retain the grafted tissue in place and promote healing, sutures are used. The sutures can sometimes result in an irregular corneal shape and this can limit the visual recovery in a clear graft.
Unless removed at appropriate times, these sutures can break and result in infection or promote rejection of the grafted tissue.
Finally, the scar due to surgery remains a permanent weakness in the coats of the eye and can rupture following trauma, even years later. Hence there has been a search for a procedure that can overcome these drawbacks of routine corneal transplantation.
Such a procedure is now available and is termed posterior lamellar corneal transplantation.
In this, the affected layers in the back of the cornea are selectively replaced and are held in place without sutures — hence, the term "sutureless" corneal transplantation.
In this approach, the surgeon removes the diseased endothelium in the centre of the cornea, using a small one mm incision in the periphery of the cornea.
New method
After undergoing DSEK.
Using special knives, the donor cornea is dissected to create an anterior 80 per cent and a posterior 20 per cent and, from this dissected tissue, a circular disc is punched using a trephine. The posterior 20 per cent of the donor cornea, which contains the endothelial cells, is then folded in half and carefully introduced into the eye through a small five mm incision in the sclera or white part of the eye.
Injections of saline are used to help the tissue unfold within the anterior chamber of the eye and a large air bubble is placed to support the tissue and help it adhere to the host corneal tissue.
The new procedure is termed Descemet's Stripping Endothelial Keratoplasty (DSEK) and helps reduce the duration of corneal transplant surgery. The absence of a full thickness corneal wound and the lack of sutures helps in better quality vision after surgery. The safety of the procedure is also enhanced — both during and after the surgical procedure.
This procedure shows promise for patients with corneal disease and is currently performed in a few centres in India.
However, as with all new procedures, it requires special instrumentation and training. The folding of the donor corneal tissue may induce some endothelial cell damage, if not performed carefully. With the advent of this procedure, corneal transplantation has entered a new and exciting phase.
The authors are consultant ophthalmologists based in Chennai.
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