The effect of Timolol 0.5% on the correction of myopic regression after LASIK

Abstract

Backgroud: Postlaser in situ keratomileusis (post-LASIK) refractive regression is defined as the gradual, partial, or total loss of initial correction that limits the predictability, efficiency, and long-term stability of LASIK. Our study assesses the effect of Timolol 0.5% on the correction of myopic regression after LASIK.

Methods: This prospective, randomized, controlled study included 62 eyes of 62 patients with myopic regression of -1.18 ± 0.86 diopters (D) after myopic LASIK. They were randomly assigned into either Group 1 who received Timolol 0.5% eye drops for 3 months or Group 2 who received artificial tears as control (during treatment). Patients were followed an additional 2 months after cessation of eye drops treatment (posttreatment).

Results: During treatment in Group 1, as the mean true intraocular pressure (IOPT) lowered significantly, regression stopped. As the mean IOPT increased significantly posttreatment and returned to its pretreatment level, regression recurred. The effective rate of Timolol therapy dropped from 62.5% during treatment to 40.6% posttreatment. On the contrary in Group 2, although the mean IOPT did not change significantly, regression continually happened as time passed. During treatment, the mean IOPT, uncorrected visual acuity, spherical equivalent (SE), and corneal refractive power showed significant difference between the 2 groups. In Group 1, the differences of effective rate of Timolol therapy between each of the 2 subgroups of age, gender, preoperative SE (PSE), or pretreatment time (how long we start treatment with Timolol post-LASIK) were not statistically significant.

Conclusion: IOP-lowering eye drop Timolol was effective for the correction of myopic regression when a 0.5-D or greater myopic shift is detected after LASIK in patients regardless of age, gender, PSE, or anytime we started the treatment only if regression happened. However, the myopic regression recurred after cessation of Timolol treatment.

Figure 1

Graph demonstrating the true intraocular pressure (IOPT) in eyes with myopic regression after laser in situ keratomileusis in the 2 treatment groups in different follow-up visits. Before treatment with eye drops (pretreatment), the difference in the mean IOPT was not statistically significant between the 2 groups (P = .715, independent samples t test). Three months after the twice-daily application of Timolol (during treatment), the mean IOPT gained 2.4-mm Hg (14.8%) reduction from the baseline (pretreatment) in Group 1 (from 16.2 pretreatment to 13.8 mm Hg during treatment, P = .000, n = 32, one-way ANOVA test) and gained 3.0 mm Hg lower than the mean IOPT in Group 2 (P = .000, independent samples t test). Two months after cessation of Timolol treatment (posttreatment), the mean IOPT in Group 1 increased significantly (from 13.80 mm Hg during treatment to 16.0 mm Hg posttreatment, P = .000, n = 32, one-way ANOVA test) and returned to its own pretreatment level (16.2 mm Hg, P = .711, n = 32, one-way ANOVA test). The difference of the mean IOPT posttreatment between the 2 groups was not statistically significant (P = .092, independent samples t test). ANOVA = analysis of variance.

Figure 2

Graph demonstrating the logarithm of the minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA) in eyes with myopic regression after laser in situ keratomileusis in the 2 treatment groups in different follow-up visits. Before treatment with eye drops (pretreatment), the difference in the mean logMAR UCVA was not statistically significant between the 2 groups (P = .667, independent samples t test). Three months after the twice-daily application of Timolol (during treatment), the mean logMAR UCVA decreased significantly in Group 1 (from 0.17 pretreatment to 0.04 during treatment, P = .000, n = 32, one-way ANOVA test) and gained 0.19 lower than the mean logMAR UCVA in Group 2 (P = .000, independent samples t test). Two months after cessation of Timolol treatment (posttreatment), the mean logMAR UCVA in Group 1 increased significantly (from 0.04 during treatment to 0.12 posttreatment, P = .016, n = 32, one-way ANOVA test) and almost returned to its own pretreatment level (0.17, P = .122, n = 32, one-way ANOVA test). But it still was significantly lower than the mean logMAR UCVA in Group 2 (P = .002, independent samples t test). ANOVA = analysis of variance, logMAR = logarithm of the minimum angle of resolution.

Figure 3

Graph demonstrating the spherical equivalent (SE) in eyes with myopic regression after laser in situ keratomileusis in the 2 treatment groups in different follow-up visits. Before treatment with eye drops (pretreatment), the difference in the mean SE was not statistically significant between the 2 groups (P = .442, independent samples t test). Three months after the twice-daily application of Timolol (during treatment), the mean SE increased significantly in Group 1 (from −1.21 D pretreatment to −0.58 D during treatment, P = .000, n = 32, one-way ANOVA test) and gained 1.04 D higher than the mean SE in Group 2 (P = .000, independent samples t test). Two months after cessation of Timolol treatment (posttreatment), the mean SE in Group 1 decreased significantly (from −0.58 D during treatment to −0.90 D posttreatment, P = .043, n = 32, one-way ANOVA test), but it still significantly was higher than its own pretreatment level (−1.21, P = .038, n = 32, one-way ANOVA test) and than the mean SE posttreatment in Group 2 (P = .000, independent samples t test). ANOVA = analysis of variance.

Figure 4

Graph demonstrating the refractive power (RP) of the cornea in eyes with myopic regression after laser in situ keratomileusis in the 2 treatment groups in different follow-up visits. Before treatment with eye drops (pretreatment), the difference in the mean RP was not statistically significant between the 2 groups (P = .913, independent samples t test). Three months after the twice-daily application of Timolol (during treatment), the mean RP decreased significantly in Group 1 (from 38.9 D pretreatment to 36.9 D during treatment, P = .018, n = 32, one-way ANOVA test) and gained 3.1 D lowered than the mean RP in Group 2 (P = .000, independent samples t test). Two months after cessation of Timolol treatment (posttreatment), the mean RP in Group 1 increased significantly (from 36.9 D during treatment to 38.7 D posttreatment, P = .036, n = 32, one-way ANOVA test) and returned to its own pretreatment level (38.9 D, P = .777, n = 32, one-way ANOVA test). The difference of the mean RP posttreatment between the 2 groups was not statistically significant (P = .069, independent samples t test). ANOVA = analysis of variance.

Figure 5

Map (Pentacam) showing the difference of corneal refractive power (RP) of an example eye in Group 1. Three months after the twice-daily application of Timolol (during treatment), the RP in the central cornea decreased (left), compared to its pretreatment level (center), 1.4 D difference of RP was observed in the central cornea (right).

Figure 6

Graph demonstrating the central corneal thickness (CCT) in eyes with myopic regression after laser in situ keratomileusis in the 2 treatment groups in different follow-up visits. Before treatment with eye drops (pretreatment), the differences in the mean CCT were not statistically significant between the 2 groups (P = .653, independent samples t test). The differences in the mean CCT ± SD among the 3 time points (pre-, during, and posttreatment) were not statistically different in each of the 2 groups (P > .05, one-way ANOVA test). ANOVA = analysis of variance.