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Purpose: Comparative evaluation of 'flap on' and 'flap off' techniques of Epi-LASIK in low-to-moderate myopia., Methods: Sixteen eyes of eight consecutive patients with myopia < or = 6 D were selected for this prospective, randomized, comparative, interventional case series. Epi-LASIK surgery was performed in all eyes. In one eye of each patient, the epithelial flap was retained after excimer laser ablation (flap on). In the fellow eye, the epithelial flap was discarded (flap off) after ablation. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SEQ), postoperative pain score, time to epithelization, and corneal haze were recorded on postoperative visits., Results: The mean preoperative SEQ in the two groups was -3.61+/-1.32 D (flap on) and -3.49+/-1.86 D (flap off; P=0.752). The mean follow-up period was 8.5+/-4.9 months. The mean pain score was comparable on all postoperative days except the second postoperative day when the group with flap off had a lesser mean pain score (P=0.053).Time for epithelial healing was 3.63+/-0.52 days in cases with flap off and 4.13+/-0.64 days in cases with flap on (P=0.113). Eyes with flap off had a better UCVA on the first postoperative day (0.19+/-0.11 logMAR) compared with eyes with flap on (0.41+/-0.28 logMAR; P=0.032). There was no significant difference in UCVA, BSCVA, SEQ, contrast sensitivity, corneal haze, and higher order aberrations at any other postoperative visit., Conclusions: There is no difference between flap on and flap off techniques of Epi-LASIK with regards to overall outcome of surgery.

Purpose: To study the risk factors for the occurrence of cylindrical prediction error (PE) after laser in situkeratomileusis (LASIK) for myopia and myopic astigmatism., Methods: The study was a nested case-control study. Five hundred eyes of 252 consecutive patients who underwent LASIK for myopia and myopic astigmatism on the Chiron Technolas 217C laser and completed 6 months of follow-up. There were 435 controls and 65 cases based on the postoperative refractive cylindrical PE. The probable risk factors studied included preoperative sphere and cylinder, keratometry, pachymetry, suction ring used, flap thickness, hinge centeration, optic zone, ablation depth, and intraoperative complications., Results: By univariate analysis, the cylindrical PE was found to be associated with preoperative spherical equivalent higher than -6 D (chi(2)=10.83; P=0.001), preoperative sphere higher than -6 D (chi(2)=6.15, P=0.013), preoperative cylinder more than -0.75 D (chi(2)=6.61; P-value=0.010), and an optic zone less than 5.5 mm (chi(2)=19.3; P=0.001). Risk factors for postoperative astigmatism by stepwise multivariate logistic regression analysis were an optic zone of less than 5.5 mm with an odds ratio (OR) of 2.81 (95% confidence interval (CI)=1.62-4.86) and preoperative cylinder more than -0.75 D with an OR of 1.60 (95% CI=0.92-2.77)., Conclusion: Postoperative astigmatism (as indicated by the cylindrical PE) is more likely to occur with an optic zone of less than 5.5 mm and a higher preoperative cylindrical error.

Aim: To study the visual performance in eyes with interface haemorrhage during laser assisted in situ keratomileusis (LASIK)., Methods: Case records of 20 patients, who had bleeding from the limbal vessels in one eye during LASIK (group 1) and uncomplicated surgery in the fellow eye (group 2) were studied. The parameters evaluated were uncorrected visual acuity (UCVA) best corrected visual acuity (BCVA), spherical equivalent of refraction (SEQ), contrast sensitivity, and glare acuity preoperatively and at 1, 3, and 6 months postoperatively., Results: The mean preoperative SEQ in group 1 and 2 eyes was -5.79 (2.3) D and -5.27 (1.68) D, respectively. The mean decimal UCVA at 6 months after LASIK in group 1 and 2 eyes were 0.6 (0.2) and 1.0 respectively (p<0.001). The mean decimal BCVA at 1 week after LASIK in group 1 and 2 eyes were 0.89 (0.04) and 1.0 respectively (p<0.05). However, all eyes had a BCVA of 6/6 at 1, 3, and 6 months after LASIK. The mean contrast sensitivity values preoperatively in group 1 and 2 eyes were 161.3 (8.7) and 172 (68.2) respectively. There was a significant decrease in group 1 at 6 months (102 (60.5) (p<0.01)) compared to group 2. The decimal glare acuity preoperatively in group 1 and 2 eyes was 0.95 (0.11) and 0.89 (0.12), respectively. It decreased significantly in group 1 (0.7) (0.1 (p<0.01)) compared to group 2 at the 6 month follow up., Conclusion: Occurrence of intraoperative interface haemorrhage may affect the visual performance following LASIK surgery.