Wednesday, April 23, 2008

Custom LASIK Answers Part 2

In a previous post I posed a question about why EyeCareOne did my exam and did their laser vision correction procedure on a dilated vs. "relaxed" eye. Last week I went back to the Laser vision correction center and was re-evaluated and I asked them this question: Why do LASIK on a dilated eye while other centers say they perform the procedure on a "relaxed" eye?

1. Their laser has a gaze-tracking feature that works better with a dilated verses the relaxed eye.

2. Have you ever seen those infomercials about a program which promises to improve your vision without the need for glasses in just minutes a day? That product is actually based on a physiologic principle called accommodation. Accommodation is the ability for the lens to change shape making images crisper and sharper. It's kind of like a fine focus which is especially important as an object in focus draws nearer to us. So, the glasses-free program sells information about using a system of "pencil pushups" and other eye exercises to help develop your ability to accommodate. This ability is usually lost or decreased in later life.

So, during my second exam, the optometrist was measuring my spherical and cylindrical correction and she had me read the eye chart after the measurement and commented, "wow, you shouldn't be able to read the chart that well." Well, one reason I was reading the chart better than predicted may have been lucky guessing but the other reason was my ability to accommodate. I guess you could say its a special talent of mine. You see, I have needed glasses since I was 5 years old, but since then, I have never consistently worn them for one reason or another. Consequently, my lens has learned to adapt and compensate or accommodate in this case.

[I wonder if I could use my new-found ability to save the world, or at least make some money?]

In any event, I quickly was convinced of how significant this phenomenon was to my vision. The optometrist proceeded to apply eye drops which dilated my pupils and paralyzed the muscles attached to my lenses. Then she had me read the eye chart again. I couldn't read it at all. Not even the big letters.

I find it curious that the other laser correction centers claim that doing LASIK on a "relaxed," non-dilated eye is better. For one thing, calling a non-dilated eye "relaxed" is a misnomer. The dilated eye is the one that is relaxed. But I think it would have been better to say "natural" because saying "relaxed" is misleading. It is misleading because had I had LASIK done based on a non-dilated exam, I would have been under-corrected. In some cases, patients can be over-corrected. However, by getting correction measurements on a dilated eye, lens accommodation is taken out of the equation as a potential confounding variable which may lead to deterioration of vision later when the ability to accommodate is lost.

If accommodation is such an significant factor in vision, I wonder why other centers ignore it. I can only speculate that it is for convenience.