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From the Chief Medical Editor

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Can Someone Please Explain Wavefront?

Paul S. Koch, M.D.

So, this girl goes to this guy's house and one thing leads to another and she decides to spend the night. His mother comes in and says, "I have a lovely guest room for you, dear," which is not what the kids wanted to hear. Only thing is the guest room has a bed with 25 mattresses piled on top of each other. Just to make things interesting, the mother secretly puts a pea between two of the lower mattresses. The next morning the girl whines that she had trouble sleeping because she could feel the pea. The mother says, "Ohmygawd, you're a princess!" And thusly are princesses discovered about 2 million times a year in the United States alone.

No wait, not that kind of princess. The other kind. Oh, never mind, but the point of the tale is that mere mortals could never notice such a subtle variation hidden well under the surface.

Which brings us to this issue focusing on refractive surgery and my need to learn this wavefront LASIK thing.

I'm still trying to figure out how it works. Like any LASIK, you begin with making a thick mattress of tissue with a microkeratome, and then you do your ablation. With wavefront LASIK, the laser also makes very subtle additional changes — so subtle you need a special machine to measure the need for them in the first place. We're talking really subtle — fractions of a micron.

Next, you put the mattress on top, a relatively thick mattress, perhaps 160 μm thick. Then I am supposed to believe that this thick flap will somehow contour itself to the very subtle submicron undulations carved into the stromal bed. Is that possible? Wouldn't the thick flap just fall down flat over the ablation, leaving small spaces between itself and the ablation contour that will eventually fill in?

But OK, let's suppose that somehow the flap manages to mold into that contour. Wouldn't its thickness mask the subtle changes so that they would be nearly uniform by the time they reach the epithelium? If the subtle changes reach the surface, wouldn't the epithelium hyperplase to make the surface smooth all over?

An Open Invitation for Answers

Wavefront laser treatments have been very successful and, as a result, the technology has amassed many devoted fans. However, if the skeptics could get clear and concise answers to the questions I have posed, many concerns about wavefront's practicality would be alleviated and these treatments would achieve a higher rate of acceptance across the ophthalmic community.