Saturday, 18 July 2009

Eye Phase 3: the cornea

I've had two visits to the eye hospital within 7 days, not because there was anything untoward but because I had appointments with different specialisations. The first was the retinal clinic where I had various tests which showed that the swelling of the macula had 'dried out'; the oedema has gone. I don't notice much improvement because I can't see much anyway for a different reason: my compromised (it's called 'decompensated' in the jargon) cornea. So the macula appears to be normal again.

A week later, I went to see Mr Au who is the specialist in corneas and corneal transplants. The cornea is the 'front window of the eye'; the part that does most of the focusing of the image which it projects onto the retina. Mine is severely damaged from all the operations I've had and because of years of glaucoma. The endothelial cells on its inner surface, if damaged, cannot renew themselves but are vital as they pump water from the cornea. If this pump isn't working, the cornea becomes waterlogged causing the blurry vision - like looking through a ground-glass screen - that I have. The only cure is to replace the endothelial cells with a graft, a new and delicate operation called a DSEK or to replace the entire cornea (full-thickness keratopathy). In either case, the graft comes from a donor, someone who has died young and generously left their eyes to be used for helping the likes of me. I already have a piece of somebody else's eye in my eye, the result of the patch graft which Miss Fenerty placed over the tube and plate she inserted to control the glaucoma - which, I am happy to say over a year later, it does effectively. As a result of this anonymous post mortem generosity, I have registered as an organ donor; the least I could do.

I had only a short wait to see Mr Au himself. He is very brisk and efficient and pleasant with it. He did several tests on different machines to enable him to determine with precision what exactly would be the best option for my eye. For various compelling reasons to do with the geometry of my 'difficult' eye, the intra-ocular lens and pupil, he feels that the best course is for me to have a full thickness keratopathy. In this operation, he makes a circular cut - using an instrument like a cookie-cutter, though a little more refined - to actually bore out a hole in the front of my eye about 7mm in diameter. Into this, he inserts a donor 'button' - the replacement cornea - which he then sutures firmly into place using very fine radial stitches. The sutures remain in place for around 18 months and I will need steroid eye drops to prevent rejection. But the new cornea should mean that I can see clearly again. At present, the image quality is so poor that I get no image fusion, no stereoscopic vision, and can barely make out the biggest letter on the standard eye chart. If I don't have this graft, the outlook is worsening vision and pain associated with the oversaturated corneal tissue. I've already had a lot of pain with this cornea and I know how unpleasant it is. The operation is not without risk but the benefits are significant.

So the choice is easy! I'm on the waiting list for an operation in about 3 months.

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