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Post Info TOPIC: LASIK and the Thin Cornea


Executive

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Date: Sun Nov 27 8:34 AM, 2005
LASIK and the Thin Cornea
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The following is an interesting article regarding surgery on thin corneas... I have recently been reading more and more that the tradional approuch... ie: Kc corneal thinness procludes surgery... Is now being amended (in some places)... it seems that there is much more to evaluate and that surgery can be successful in certain instances (mini ark being but one example)... this article is of interest as it talks about the strength of corneal tissue as apposed to its thickness.
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LASIK and the Thin Cornea

CRST June 2005
By Lee T. Nordan, MD
The crux of the matter is to decide whether a 500-µm thick cornea without overt corneal irregular astigmatism is normal or abnormal. Experience reveals that many high myopes have a normal cornea of 510µm. I would submit, however, that a corneal thickness of 500µm is more than three standard deviations from the norm. By definition, it is an abnormal cornea. The standard deviation to the thick side is much greater than to the thin side. For example, if the average cornea is 520µm, the standard deviation to the thick side might be 20µm but only 7µm to the thin side (virtually all corneas that are 490µm thick have keratoconus, but those that are 600µm thick are normal). I believe that my clinical experience supports this concept.Clinically, there can be no doubt that a cornea with a central thickness of 500µm has a much greater chance of developing irregular astigmatism (mild ectasia) after LASIK compared to a cornea with a preoperative central thickness of at least 515µm. The problem occurs because the cornea is not of normal strength preoperatively and cannot resist the IOP and retain the proper shape after LASIK. If the cornea is 500µm thick and of normal strength, then LASIK will be successful in the long term. Unfortunately, it is not possible to distinguish preoperatively between the strong (normal) or weak (keratoconic) cornea.About 20 years ago during the keratomileusis era, I discussed this issue with Richard Troutman, MD, and we referred to it as 20/20 keratoconus. The patient has 20/20 vision without irregular astigmatism but has hidden collagen weakness. The lamellar procedure weakens the cornea enough to allow for ectasia. We made several attempts to judge the strength of patients’ collagen by methods such as a skin biopsy and skin laxity over the proximal knuckle of the third finger. None of these attempts produced any worthwhile information.If mild irregular astigmatism is present preoperatively, then a diagnosis of keratoconus is easy. Very often, mild irregular astigmatism is more easily observed with a manual keratometer than with an automated topographer.HOW TO PROCEEDIn my opinion, it is prudent to perform a surface laser procedure on “normal” corneas that have a central corneal thickness of 505µm or less. This strategy will probably avoid unexpected ectasia. Whether the percentage of thin corneas that have a hidden collagen defect is 5% or 50%, LASIK is too risky.This question of LASIK and the thin cornea points out that a true refractive surgeon must perform the procedure that is most appropriate for a given case. An ophthalmologist who performs only LASIK is not a comprehensive refractive surgeon but merely a LASIK surgeon. Quality refractive surgery demands that the surgeon’s ego or quest for the wow factor not be the dominant force in selecting the procedure. Rather, ophthalmologists should make a prudent decision as to the refractive procedure of choice, which entails the least risk and the likelihood of an excellent result.

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Anonymous

Date: Mon Dec 5 7:39 AM, 2005
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hmmm "20-20 keratoconus"... they say... that makes kc not rare at all in my books... a ticking time bomb?... as it could advance at any time?


...and on a another note... some of my close buddy knows what i'm talking about with regards to some-one who was refused lasik due to there kc... and then after mini-ark... they where deemed as getting enough corneal thickness back due to mini-ark, to have lasik, to correct their long sightness after their kc has been sorted out (kc causes short-sightedness... the guy had kc and long-sightness as an additional problem... about 10% of kcers are long sighted also apparently) So the guy went "full circle" and has had lasik and is very happy with his out come .... Just Amazing! ...please note it took him five visits to Rome and a lot of dedication on his part ...which is not for the faint hearted amoung us! (He said that he will post his story, soon hopfully)



-- Edited by QuintriX at 00:13, 2005-12-07

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Senior Member

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Date: Fri Dec 9 4:01 AM, 2005
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20-20 Keratoconus. An eye allergy, a lot of eye rubbing and hey presto you now have 20/80 keratoconus.



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Senior Member

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Posts: 121
Date: Thu Dec 22 8:12 PM, 2005
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I keep asking my father (a Retinal Opthal) why not a LASIK for my KP poor vision left eye ? Graft is clear & thick, hence again why not? replies ' very risky, not at all advised '

-- Edited by Eapen at 05:05, 2005-12-29

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Senior Member

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Posts: 139
Date: Mon May 14 4:44 PM, 2007
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I was debating saving up for lasik for my graft eye...part of me wanted to look into it and part of me felt guilty..[for being so vain and that i was being disrectful to my graft doner]

Anyway I recently got cataract so will go blinder than ever..[though that could be 50 years] so i doubht lasik is an option now...

I would love to see people on kc boards who have had lasik after a graft to see how they did after it..


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Veteran Member

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Date: Mon Aug 8 7:00 PM, 2016
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If you are showing symptoms of cataracts, be aware that the visual degradation sneaks up on you as the progression is gradual. I went in for a checkup because I thought my KC was getting worse only to be told the issue was cataracts. They weren't even mentioned by my optometrist at my checkup less than a year earlier, although they had been observed a few years before that. When they operated, the surgeon commented that the cataract was worse than he was expecting.

If you have only normal visual acuity issues with your graft, then there is a good chance that they can implant an "advanced IOL" when the time comes for cataract surgery and provide you with excellent vision. Following my cataract surgery they were able to give me better than 20/30 vision in the eye with mild KC. They were way off in the other eye though, so I wear one contact lens to correct KC, hyperopia, and anisometropia. On a positive note, I have no trouble qualifying for medically necessary contact lenses!

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