[Preliminary study on preventive effects of timolol on myopic regression after laser in situ keratomileusis]

To assess the preventive effects of early timolol eye drops application in patients after laser in situ keratomileusis (LASIK).

Sixty patients (60 eyes) were randomly assigned to the treatment group and the control group. Timolol was administered topically twice per day to the treatment group from the second week through the end of the first month. We observed the changes of intraocular pressure (IOP), spherical equivalent correction (SE), stimulated curvature (Simk), anterior chamber depth (ACD) and different value (Diff) both preoperatively and postoperatively, i.e. before and 1 week after LASIK, 1 month and 3 months after LASIK, respectively. All examinations were completed in person. Independent-samples T test, repeated-measures ANOVA, one-way ANOVA were used for statistical comparisons. Significance level was set to α = 0.05.

The manifest refraction of treatment group was (-0.07 ± 0.25) D, (0.04 ± 0.21) D and (-0.05 ± 0.12) D, respectively, while the control group was (-0.08 ± 0.22) D, (-0.15 ± 0.17) D and (-0.14 ± 0.18) D, respectively, at 1 week, 1 and 3 months postoperatively. The difference between the two groups was significant (F = 5.68, P < 0.05) regardless of time. The IOP of treatment group was (12.63 ± 2.56) mm Hg (1 mm Hg = 0.133 kPa), (9.70 ± 1.88) mm Hg and (11.41 ± 1.22) mm Hg, respectively, at 1 week, 1 and 3 months postoperatively. The control group did not change significantly throughout follow-period. The changes of treatment group was significant in different periods (F = 34.62, P < 0.01). After surgery, the posterior corneal surface of the treatment group displayed mean forward shift of (35.73 ± 14.55) µm and the control group did (45.80 ± 19.86) µm (t = 2.83, P < 0.05). The stimulated curvature (Simk) and anterior chamber depth (ACD) was not significantly different between the two groups at any postoperative visit.

Our prospective study demonstrates that timolol is effective to stabilize the refraction after LASIK. Reduction of IOP and corneal ectasia may play a significant role in preventing myopic regression.