ABSTRACT
Background Refractive regression is a common complication of high myopia after laser in situ keratomileusis (LASIK),and it affects the stability of surgery.Objective This study was to observe the preventive effect of timolol on refractive regression in high myopia after LASIK.Methods A perspective randomized controlled trial was performed under the approval of Affiliated Hospital of Zunyi Medical College and the informed consent of the patients.Sixty eyes of 60 patients with high myopia (-7.16±0.95) D for LASIK were randomized into experimental group and control group.Regular eye drops were topically administered in the patients after LASIK in both groups,and timolol 0.5 ％ was added topically from 1 day after LASIK.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA),spherical equivalent (SE),corneal anterior surface curvature,intraocular pressure (IOP),central corneal thickness (CCT) were measured before LASIK,1 week,1 month,3 months and 6 months after LASIK,respectively.Residual stromal bed thickness was calculated before LASIK.The differences of above-mentioned indexes were analyzed and compared between the two groups and among the various time points using repetitive measurements analysis of variance,independent simple t test and Bonferroni test.Results No significant differences were found in the demography between the experimental group and the control group,including age,UCVA,BCVA,SE,IOP,corneal anterior surface curvature,CCT and residual stromal bed thickness (all at P＞0.05).UCVA was significantly different between the two groups among various time points (Fgroup =3.91,P＜0.05 ; Ftime =3.80,P＜0.05),and the UCVA was significantly higher in the experimental group than the control group 6 months after LASIK (t=2.97,P＜0.05),and UCVA was gradually increased as the lapse of postoperative time with the significant difference between 7 days and 6 months after LASIK in the experimental group (P＜0.05).No significant difference was seen in the BCVA between the two groups at various postoperative time points (Fgroup =2.44,P＞0.05;Ftime =2.31,P＞0.05).SE refraction in both groups were significantly reduced from 7 days through 6 months after LASIK,showing significant difference between the groups at various time points after LASIK(Fgroup =11.52,P＜0.05;Ftime =22.06,P＜0.05).The SE refraction was higher in the experimental group than that in the control group 6 months after LASIK (t =2.47,P＜0.05).Corrected IOP in the experimental group was lower than that of the control group at 7 days,1 month and 3 months after LASIK,respectively (Fgroup =14.83,P＜0.05).The change of CCT was not statistically different between the control group and the experimental group (Fgroup =0.04,P＞0.05).The anterior corneal surface curvature was steady in the experimental group during the following-up duration after LASIK,while the control group was growing gradually (Ftime =18.73,P＜0.05).Conclusions The study data show that topical administration of 0.5％ timolol early in high myopia following LASIK is effective for the reduction of the refractive regression.It is suggested that 0.5％ timolol can prevent cornea ectasia by lowering IOP.Reduction of the IOP may contribute to improving the regression after keratorefractive surgery in high myopic eyes.