Laser-assisted in-situ keratomileusis with iris registration against manual limbal markings for the correction of myopic astigmatism

Purpose The aim of this study was to compare the refractive outcomes and visual acuity of laser-assisted in-situ keratomileusis (LASIK) with static preablation iris registration (IR) and LASIK with that of manual limbal markings (LM) in the management of myopic astigmatism. Setting The study was carried out at El-Safwa Laser Vision Center in Alexandria, Egypt. Patients and methods This prospective randomized clinical study was conducted on 40 eyes that were divided into two groups. Group A (IR group) was treated with LASIK procedure with preablation static IR (software of WaveLight EX500 Excimer laser) in conjunction with the Topolyzer Vario to automatically detect and adjust cyclotorsional misalignment. Group B (LM group) was treated with LASIK with the same machine without using the IR software and instead using a corneal marking pen for LM for manual cyclotorsional misalignment adjustments. Refraction and visual acuity data were compared between groups at the first, third, and sixth postoperative months. Vector analysis was performed by the Alpins method using data from the third postoperative month. Results The mean preoperative spherical error was −2.75±1.84 and −3.05±2.67 D in the IR group and the LM group, respectively (P=0.946). The mean preoperative cylindrical error was −2.65±0.81 and −2.31±0.41 D in the IR group and the LM group, respectively (P=0.170). At the sixth postoperative month, the mean spherical error of the IR group was −0.06±0.29 D, whereas that of the LM group was −0.08±0.24 D (P=0.822). The mean cylindrical error of the IR group was −0.43±0.23 D, whereas that of the LM group was −0.38±0.21 D (P=0.353). There was no statistically significant difference between the two groups regarding manifest refraction, best corrected visual acuity, uncorrected visual acuity, and safety index at all postoperative time points. There was no statistically significant difference between the two groups regarding target-induced astigmatism, difference vector, magnitude of error, angle of error, and predictability at 3 months postoperatively. However, the surgically induced astigmatism and efficacy were statistically significantly higher in the IR group at 3 months postoperatively. Conclusion Using the EX500 Excimer laser system, LASIK with IR software is as safe and predictable as LASIK with LM in the treatment of myopic astigmatism.