Just commenting on the discussion re corneal scarring ...
There are several types of corneal scarring and indeed scarring is part of the conventional definition of keratoconus. Hydrops is a major cause and indeed Lea's scarring appears to be due to this.
However, Gareth also has a point about rigid lenses possibly causing scarring. It has long been debated whether rigid contact lenses themselves contribute to a) scarring and b) actively progressing KC. The long term CLEK study of KC in the US implicated rigid lenses on both counts and for quite a while, contact lenses were regularly quoted as one of the causes of KC.
The problem with this subject is that there are no definitive studies comparing contact lens wearers and non lens wearers... for fairly obvious reasons! It is almost impossible to find anyone in the US or UK who is keratoconic and who has not worn some form of contact lens correction - and most research is done in these two countries. However, I HAVE worked in a country where KC incidence is high yet a large number of keratoconics do not wear contact lenses. It was there that I noticed that such patients did not have a particular type of scarring. Yes, they had the irregular scarring typical of Hydrops or as a result of eye rubbing - but they did not have the characteristic circular "scuff" scarring so typical of KC RGP wearers I had seen in the UK - many my own patients. I tried very hard to get researchers interested in studying this population but there was absolutely no interest from the UK or US.
It was because of this issue that I looked harder at correcting KC with soft contact lenses and more lately with Silicone Hydrogel lenses. And I have found that such characteristic scarring actually reduces when patients are swapped to SiH lenses, as does photophobia and general discomfort. I have some examples on my
website.
Now of course this is an emotive issue. There is strong evidence that correctly fitting RGPs (i.e lenses that clear the cone rather than bear down on it) do not damage the cornea in this way - it is flat fitting lenses that do the most damage. So, fitters who really know what they are doing and keep a close eye on their patients rarely see the problem.
However, there is also increasing evidence (eg Klyce, 2000) that apical clearance RGPs actually cause a vacuum effect when they flex on blinking and that this can cause a steepening of the cornea. Thus a good fitting lens can become a flat fitting lens within around 6 months. Add into this mix the fact that flat fitting lenses give better vision than apical clearance ones, and you get a situation where patients "twig"that a better fitting lens means worse vision and thus they tend to avoid coming back....
Many practitioners have tacitly accepted this situation over the years because frankly, there was not much else you could do about it. Patients had to see and there were not many other options. However, this is not now so. More and more contact lens options are now available that try and avoid corneal bearing - such as the SoClear, sclerals and the new Synergeyes ClearKone. The latter says in its PR -
the design is optimized to vault the predominant irregularities of the keratoconic cornea, thus effectively restoring vision to a vast majority of irregular cornea patients, without compromising comfort or eye health, even in the most challenging cases. This is because it is designed to vault the cornea and thus not bear down on it.
I myself have decided that I will not fit any new cases of KC in rigid lenses - more fully explained in my new
blog. This is after several years of tracking corneal scars versus lens types and particularly tracking patients who do only wear a lens in one eye. Many don't wear a lens in the worst eye as they simply cannot tolerate one... and its uncanny how often the worse eye may have hydrops scars but NOT the circular on axis central scars that the RGP wearing eye has.
Obviously more research needs to be done - but its a difficult one to do in this country because, really, you would have to have controls in no lenses at all...
Lynn