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R. Solomon, E. Donnenfeld, A. Nattis, G. Fishman, J. Roth, J. Stein, M. McDonald; The Effect of Cyclotorsion and Pupil Centroid Shift on Excimer Laser Photoablation: Analysis of 1000 Patients. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2362.
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To evaluate the magnitude and importance of cyclotorsional registration and pupil centroid shift compensation on excimer laser photoablation.
Cyclotorsion, pupil centroid shift, and pupil size changes were measured in 1193 consecutive eyes undergoing LASIK with the VISX S4 IR between their wavefront capture and at the time of surgery. The LASIK flaps were created with the Amadeus II microkeratome or the IntraLase femtosecond laser and the data were retrospectively gathered from a chart review.
Iris registration was achieved in 93% (83/1193) of eyes. There was no statistical difference between registration achieved with the Amadeus II microkeratome 94.6% (581/614) and the IntraLase femtosecond laser 91.4 % (529/579). Mean cyclotorsion between wavefront capture and ablation was 3.21 +/- 2.1 degrees with a range of 0-9.7 degrees. Mean X and Y axis pupil centroid shift was 0.26 +/- .13 and 0.13 +/- .08 microns with a range of 0-0.5 microns. Mean wavefront pupil size was 6.63 +/- .86 mm and mean treatment pupil size under minimal illumination was 3.56 +/- .66 mm.
Wavefront data must be centered on a fixed eye structure rather than the pupil center and cyclotorsion must be accounted for to ensure that wavefront data captured is appropriately matched to the pupil at the time of surgery. Otherwise, clinically significant decentration of the wavefront between capture and excimer laser application is possible.
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