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Corneal transplants and Keratoconus

 

Corneal transplants have been refined to an exceptionally high level of expertise over the years, and keratoconus is the major single indication. For other conditions, the surgeon is usually dealing with a seriously unhealthy cornea which may be opaque and vascularised. There is a tendency for the cornea to become scarred in keratoconus as well, but by how much varies from person to person. Sometimes there is hardly any after a lifetime of contact lens wear, sometimes it happens so rapidly that there is no useful vision even when there has been little or no contact lens wear. So, there is very little to gain by trying to predict how quickly such changes are likely to occur.

There is a significantly greater chance of a successful outcome for keratoconus than any other corneal condition because the cornea is ectactic (thin) and distended, but otherwise avascular and essentially healthy, at least from a metabolic point of view. However, for exactly these reasons, there is also more to lose, especially as there may be an alternative treatment option available.

Transplant outcome

For keratoconus, when the success rate is discussed, a fair and honest answer is to say that 95% survive. However, it is a really complex issue and that is a meaningless statistic on its own. For a start, there is not much information about how long they last. The known outcome is generally stated at five years post op, ie 95% are known to survive that period. People move, and some do not attend follow up.  The fact is that it is not easy to collect conclusive information. I know some centres state a higher survival rate, and I am also aware that many transplants have lasted much longer than five years. However, anecdotal data does not stand up to statistical scrutiny.

Defining success, failure and survival

Then there is the question of defining the outcome. There was a time, not that long ago, when if the graft was clear, it was successful and if it was not clear, it was unsuccessful. Nice and simple. There may have been 25.00 dioptres of astigmatism, or the eye was not used post op for some other reason, but that did not seem to be an issue. Hence the expression in the previous paragraph . survival . rather than success. In fact, I was once picked up by one of the consultants on that point when giving a presentation. I floated the success rate of 95% as a discussion point, to which the reply came, 'You mean survival'. Quite right too.

Survival is relatively easy to define, but success is a different matter. About 50% of post transplanted corneas need a contact lens for the best visual result. If the cornea is clear, the vision with a contact lens may be better than could be expected pre-op. Somewhere between a sixth and a fifth of the scleral lens wearers I know are post transplant, totalling not far off 200. Keratoconus sufferers who are fed up to the back teeth with contact lenses may not agree that still needing them post op constitutes a successful outcome.

The debate 'scleral lenses or transplant' is shaky. They have advantages and drawbacks compared to corneal RGP lenses, but the presumed progression . RGP corneal lenses,  . sclerals, then if they fail,  . a transplant, is not the right way to look at it. The reality is that modern RGP sclerals are an option for contact lens management of keratoconus at all levels. There are quite a few in the group who have worn sclerals for over fifty years. Those who started before the war would have had lenses made from glass!

15 years ago it was true that sclerals were only seriously only considered feasible in the most advanced cases, but now it is just as likely to find people switching between sclerals and corneals. Sometimes sclerals are worn for a few months or years due to intolerance to corneals, but have another try later and find them better, eg Jackie's story in the discussion page recently. If there was a competition between the two types, sclerals just went one down. More to the point is the combination of both, along with Jackie's own efforts under difficult circumstances, have kept her going for a few years, and she has avoided the operating table.

It is great to see such lively debate on the web site about the options available for treatment for keratoconus. I hope you don't mind a contribution from the 'other side'.

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Page last updated: 19 February, 2015