| Abstract (english) | Purpose: To calculate the surgically induced astigmatism (SIA) following LASIK and identify any association between SIA and the target induced astigmatism (TIA) at 1 year postoperatively. Methods: The SIA was calculated using the TIA and residual astigmatism values for [A] myopic astigmatism and [B] mixed astigmatism treated with either the [I] WaveLight Allegretto EyeQ 400-Hz (Alcon Laboratories, Inc. Fort Worth, TX) or [II] Schwind Amaris 750S (Schwind eye-tech-solutions, Kleinostheim, ... More Germany) platforms. The TIA and corresponding SIA results were analyzed using various techniques. Results: Key findings were the negative SIA power (y1) was significantly correlated with negative TIA power (x1) and sine of the TIA axis (x2) as follows: [A] I, y1= 0.829x1-0.403x2-0.325 (F = 87.76, r = 0.804, P < .001, n = 127) ; II, y1= 0.891x1-0.037x2-0.192 (F = 240.06, r = 0.901, P < .001, n = 119) and [B] I, y1= 1.063x1+0.233x2+0.411 (F = 990.99, r = 0.881, P < .001, n = 61) ; II, y1= 1.029x1-0.115x2+0.322 (F = 270.12, r = 0.908, P < 0.001, n = 111). The sine of negative SIA axis (y2) was significantly correlated with negative TIA power (x1) and TIA axis (x2) as follows: [A] I, y2 = 0.951x2- 0.007x1+0.008 (F = 446.58, r = 0.950, P < .001, n = 127) ; II, y2 = 0.856x2+0.007x1+0.105 (F = 277.18, r = 0.912, P< .001, n = 119) and [B] I, y2 = 0.953x2+0.009x1+0.075 (F = 362.6, r = 0.963, P < .001, n = 61) ; II, y2 = 0.977x2-0.004x1+0.002 (F = 2910.9, r = 0.990, P < .001, n = 111). Conclusions: The predicted SIA power was up to 12% less than expected in cases of -6.00 diopters cylinder treated for myopic astigmatism using the Allegretto platform. The mean predicted angle of error (the angle between the SIA and TIA axes) was less than 4°, increasing to 12° for against-the- rule astigmatism. The Allegretto platform tended toward a clockwise axis rotational error, whereas the Amaris platform tended toward the opposite. [J Refract Surg. 2017 ; 33(2):104-109.]. Less |
