thin corneas monovision intralase

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thin corneas monovision intralase

Postby GeneralPatientInquiry » Sat Jun 03, 2006 9:36 pm

I am 56 years of age and have thin corneas, R=454, L=460. Myopia/astigmatism R -5.75 +0.50 x135 and L -5.00 +0.50 x135. Pupil size 6mm both eyes.

I was told I am a candidate for LASIK. Right eye using Visx Star S4 Customview, using intralase to make the flap and Left traditional LASIK with intralase because I decided on monovision and Customview not FDA approved for monovision. I was told the computer would determine the ablation and transition zone at time of surgery, but estimated 13-15 microns of tissue removal per diopter of myopia. Traditional method removing less.

The group of doctors I am seeing is supposed to be the best in my area. The Lasik coordinator did seem surprised at my questions, told me that computer would not do the LASIK if my numbers were not acceptable and they did do an additional test because of my thin corneas (cornial cell count).

I still have concerns and would appreciate your opinion and any additional information you can provide.

This post is a reprint of a previously requested inquiry received by via email.
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Postby LasikExpert » Sat Jun 03, 2006 9:40 pm

Your concerns are valid, but some may have been accommodated by the doctor's selection of technology and technique.

If you have read our article about Lasik Pupil Size then you understand the importance of pupil size when compared to the size of the optical ablation zone. The Visx S4 has the ability to correct both your myopia (nearsighted) and astigmatism with an optical ablation zone that is equal to your 6.0mm pupil size. The Visx laser in conventional mode (Visx S3) MAY not be able to accommodate your myopia and your astigmatism within the desired 6.0mm.

The reason the Visx S3/conventional may not be able to accommodate your 6.0mm pupils is because the Visx S3 makes an elliptical ablation to correct astigmatism. The narrow width of this elliptical treatment zone is smaller than the width of the ablation zone for myopia. So it is possible that the optical ablation zone for myopia on your left eye will be 6.0mm, but the ablation zone for correcting your astigmatism would be 5.5mm X 6.0mm. Remember that optical ablation zone does not include any transition or "blend" zone.

Depending upon your doctor's planned treatment, this may or may not be an issue. All you need to ask is if the smallest size of the smallest width of the smallest optical ablation zone to correct your myopia AND your astigmatism will be equal to or larger than your naturally dilated pupil.

The use of the femtosecond laser to create the flap is wise, if LASIK will be performed. Intralase creates a flap with more accuracy than a mechanical microkeratome and a thinner flap can be created. This will help accommodate your somewhat thin corneas.

My question to you and your doctor is why you are not selecting a surface ablation technique such as PRK or its cousins LASEK and Epi-LASIK? Surface ablation eliminates the flap altogether (and the possibility of any flap related complication), would increase the amount of untouched cornea by at least 100 microns, and may provide a better long-term result than LASIK. There is a longer recovery time and more discomfort, but your situation seems appropriate to consider surface ablation.
Glenn Hagele
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