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A patient came in with a problem called keratoconus. That is an abnormality in the cornea in which the cornea becomes an abnormal shape. The cornea starts to herniate and bulge in an abnormal way, sort of like a tire blowing out. It starts to bulge out where the tire gets thin, and that’s sort of what happens with the cornea. The cornea becomes thin in an area, and then it allows that part of the cornea to bulge forward, which then causes your vision to blur.
Someone who has keratoconus has irregular astigmatism. Regular astigmatism means your eye is shaped sort of like a football cut in half. It’s more rounded on one side and flattened on the other, but it’s symmetrical.
When people have irregular astigmatism, that relationship is not consistent. It’s abnormal. We now have herniated or bulge in certain areas. It’s difficult for glasses to correct vision in someone like that because it’s not symmetrical astigmatism, which is what almost all cases of astigmatism are. If the irregular astigmatism gets severe enough, then glasses cannot correct the vision of a person with keratoconus.
Keratoconus is a multifactorial disease; that is, we’re not sure exactly what the cause is. There’s some evidence that some enzymes in the cornea are activating and thinning it. There is also an autosomal dominant form of inherited keratoconus. Also, there is a study Dr. Croley thinks is out of Duke University where a corneal specialist there had a clinic for all these keratoconus patients and he was noticing that they’re all sitting here rubbing their eyes severely (a knuckle on the eye and rubbing it) and he thinks that there’s some evidence that trauma, that is, chronically rubbing on the eye with your knuckle, causes the cornea to be damaged, lose its integrity, and then cause the thinning and herniation.
There are multiple factors about keratoconus and how it is caused. Usually, it’s bilateral, that is, it’s in both eyes, but Dr. Croley has seen a couple of cases where it’s only unilateral.
If someone has keratoconus at the point where the glasses won’t correct their vision anymore, what’s the next step?
Contact lenses have advanced. In the beginning, to correct irregular astigmatism, we had to fit a gas perm or hard-type lens over the cornea so that way, it would vault over that herniation, and your tears would fill in the gap, and so then it would straighten someone’s vision out. Sometimes, they get uncomfortable because the cornea gets so steep that they become difficult to wear. Now there’s a newer generation of lenses where actually there’s a soft lens on the periphery, then in the center is a gas permeable blended into that soft lens. So now you have a more comfortable soft lens on the peripheral part of your eye, and then the gas permeable in the middle to correct the vision.
A plain soft lens doesn’t correct the astigmatism from keratoconus very well because it drapes over the eye and follows the same structure or curvature of your cornea.
Now, there are toric lenses that can be used for a while in some cases with irregular astigmatism due to keratoconus, but eventually, if the keratoconus progresses, they typically don’t work.
What are the other treatments, as far as keratoconus goes? One FDA-approved treatment is cross-linking. So basically, you know, the cornea now is thin, and its structure is getting weak, and so the textile strength of the cornea is being diminished.
Cross-linking involves instilling riboflavin into the eye, then exposing the cornea to UVA light for about 30 minutes. This has been shown to strengthen the collagen in your cornea and stop the progression of keratoconus. The studies that have been done look very good, and that’s gonna be a non-surgical way of correcting or stopping the progression of keratoconus.
Then you have surgical procedures. One surgical procedure is an Intac, where a sort of splint is placed inside the cornea, strengthening it or providing support like a crutch, helping people maintain better vision.
The final thing is a corneal transplant. A tissue in the center part of the cornea is removed, and a donor cornea is placed and sutured in place. Then there are other procedures where only the superficial layers are added on, which is called DLK. There is also epikeratoplasty, where corneal tissues are put on top of the cornea, and that has had a sort of mixed success.
If you have questions about keratoconus or anything else, you can always ask us. You can contact us through the website. If not, may God bless you with healthy eyes and great vision.
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