Abstract
Abstract: :
Purpose: To investigate theoretically the influence of the relation between pupil and optical zone (OZ) diameter, referred to as pupil excess (PE), on higher order wavefront aberrations (HOA) after wavefront guided LASIK. Methods: 19 moderately myopic eyes of 14 patients (-5.25 to -6.88 D; spherical equivalent [SE] -6.31±0.48 D) which underwent uneventful wavefront-guided LASIK (Zyoptix, Bausch & Lomb) were included. The mean OZ diameter was 6.37±0.5 mm (5.7-7.1 mm). Wavefront measurements were performed with a HARTMANN-SHACK sensor in maximal mydriasis preoperatively and 12 months after LASIK. The root mean square (RMS) wavefront error was computed for total HOA (3rd to 5th order) and for spherical aberration (Z 4,0) for pupil diameters of 3, 3.5, 4, 5, 6 and 7 mm, for the individual OZ diameter and for the individual maximum (7.83±0.42 mm). A multiple regression model was applied to determine influence of different factors on changes in HOA. The impact of PE was described using curvilinear regression with a 4th order polynomial fit. Results: The difference (post- vs. preoperative) of HOA and Z 4,0 (ΔHOA and ΔZ 4,0, respectively) was correlated with PE (ΔHOA: r²=0.69, p<0.001; ΔZ 4,0: r²=0.89, p<0.001). ΔHOA and ΔZ 4,0 were correlated higher with PE than analysis diameter (r²=0.41; 0.76), SE (r²=0.00; 0.00), OZ diameter (r²=0.03; 0.00) and preoperative HOA RMS (r²=0.02; 0.03). Conclusions: Also for wavefront-guided LASIK maximal optical zone diameters should be chosen to minimize the amount of induced HOA postoperatively.
Keywords: refractive surgery: optical quality • refractive surgery: LASIK