Timolol to Treat Myopic Regression After LASIK
Timolol to Treat Myopic Regression After LASIK
Shojaei A, Eslani M, Vali Y, Mansouri M, Dadman N, Yaseri M
Am J Ophthalmol. 2012;154:790-798
Shojaei and colleagues performed a prospective, randomized, placebo-controlled, double-masked clinical trial evaluating the efficacy of timolol 0.5% drops vs artificial tears to treat regression after LASIK surgery for myopia. The LASIK was performed with a Technolas 217-Z excimer laser. The LASIK flap was fashioned with a Moria M2 mechanical microkeratome.
Each group included 51 eyes, and 45 eyes in each group completed the study. The mean preoperative spherical equivalent (SE) was approximately -8 diopters (D) in each group. Patients were entered into the study an average of 5 months after their LASIK surgery (range, 1-15 months). The mean degree of myopic regression in both groups was approximately -1.5 D.
In the timolol-treated eyes, the mean SE declined from -1.48 D to -0.88 D after 6 months of timolol. The SE remained stable at -0.86 D for 6 months after the timolol was discontinued. This reduction was statistically significant (P < .001). In the placebo-treated eyes, the mean SE became progressively more myopic from -1.57 (pretreatment) to -1.83 (6 months after treatment) to -1.91 (6 months after discontinuation of timolol; all P < .001). The effect of timolol diminished the longer after the LASIK it was started by approximately 0.25 D for every 4 months after the procedure (P < .001). The investigators concluded that topical timolol 0.05% twice daily for 6 months was effective to reverse small degrees of myopic regression after LASIK surgery, and the effect lasted for at least 6 months after the medication was stopped. The earlier after the LASIK surgery that timolol is started, the greater the effect.
Although the refractive results of LASIK surgery for myopia are generally excellent, postoperative regression can occur, especially when higher degrees of myopia are being treated. Regression is defined as myopia developing after achieving an excellent refraction soon after surgery, as opposed to undercorrection, in which full correction was never achieved. Regression is quite frustrating for patients (who initially had excellent uncorrected vision only to have it disappear) and surgeons (who now have to deal with unhappy patients). Regression is often managed with glasses or contact lenses; however, patients are often dissatisfied with these solutions.
Exactly why regression occurs is not known. One theory is that because LASIK weakens the cornea, the intraocular pressure (IOP) actually causes the anterior and posterior corneal curvatures to bulge slightly, resulting in corneal steepening and regression. If that were the case, then reducing the IOP might treat regression after LASIK. Shojaei and colleagues demonstrated that timolol 0.5% twice daily can reverse myopic regression by approximately 0.6 D, whereas in the control eyes, myopia progressed by approximately 0.3 D. The effect of the timolol was statistically significant in the low and moderate myopia groups (up to but not over -10 D). The IOP declined from 13 mm Hg to 10 mm Hg during the 6 months of timolol treatment and reverted back to 13 mm Hg after it was stopped. The IOP did not change in the control group. They also showed that the refractions remained stable for 6 months after timolol was stopped.
The investigators measured corneal thickness, which did not differ between the 2 groups at any time in the study. However, they did not measure anterior or posterior corneal curvature. Therefore, that the reduced IOP led to a change in corneal curvature and thus reduced refractive regression can only be assumed. Why didn't the refractive regression continue after the timolol was discontinued and the IOP returned to baseline? The investigators postulate that by that time corneal healing had occurred, which strengthened the cornea enough so that it didn't bulge as much from the IOP. It would be helpful to confirm this possibility with corneal curvature measurements.
How can we use the results of this study in clinical practice? We should think about using timolol in eyes with mild-to-moderate degrees of refractive regression after myopic LASIK, especially if it is discovered in the first few months of the LASIK procedure. Timolol treatment probably won't work as well in more myopic eyes with higher degrees of refractive regression. In those eyes, surgical enhancement should be considered when the refraction is stable.
This raises the question of whether other IOP-lowering medications would work as effectively as timolol, which has occasional systemic side effects, as well as whether timolol (or another IOP-lowering medication) would work for refractive regression after myopic surface ablation, such as photorefractive keratectomy or epi-LASIK. These are excellent questions for future studies.
Abstract
Effect of Timolol on Refractive Outcomes in Eyes With Myopic Regression After Laser In Situ Keratomileusis: A Prospective Randomized Clinical Trial
Shojaei A, Eslani M, Vali Y, Mansouri M, Dadman N, Yaseri M
Am J Ophthalmol. 2012;154:790-798
Study Summary
Shojaei and colleagues performed a prospective, randomized, placebo-controlled, double-masked clinical trial evaluating the efficacy of timolol 0.5% drops vs artificial tears to treat regression after LASIK surgery for myopia. The LASIK was performed with a Technolas 217-Z excimer laser. The LASIK flap was fashioned with a Moria M2 mechanical microkeratome.
Each group included 51 eyes, and 45 eyes in each group completed the study. The mean preoperative spherical equivalent (SE) was approximately -8 diopters (D) in each group. Patients were entered into the study an average of 5 months after their LASIK surgery (range, 1-15 months). The mean degree of myopic regression in both groups was approximately -1.5 D.
In the timolol-treated eyes, the mean SE declined from -1.48 D to -0.88 D after 6 months of timolol. The SE remained stable at -0.86 D for 6 months after the timolol was discontinued. This reduction was statistically significant (P < .001). In the placebo-treated eyes, the mean SE became progressively more myopic from -1.57 (pretreatment) to -1.83 (6 months after treatment) to -1.91 (6 months after discontinuation of timolol; all P < .001). The effect of timolol diminished the longer after the LASIK it was started by approximately 0.25 D for every 4 months after the procedure (P < .001). The investigators concluded that topical timolol 0.05% twice daily for 6 months was effective to reverse small degrees of myopic regression after LASIK surgery, and the effect lasted for at least 6 months after the medication was stopped. The earlier after the LASIK surgery that timolol is started, the greater the effect.
Viewpoint
Although the refractive results of LASIK surgery for myopia are generally excellent, postoperative regression can occur, especially when higher degrees of myopia are being treated. Regression is defined as myopia developing after achieving an excellent refraction soon after surgery, as opposed to undercorrection, in which full correction was never achieved. Regression is quite frustrating for patients (who initially had excellent uncorrected vision only to have it disappear) and surgeons (who now have to deal with unhappy patients). Regression is often managed with glasses or contact lenses; however, patients are often dissatisfied with these solutions.
Exactly why regression occurs is not known. One theory is that because LASIK weakens the cornea, the intraocular pressure (IOP) actually causes the anterior and posterior corneal curvatures to bulge slightly, resulting in corneal steepening and regression. If that were the case, then reducing the IOP might treat regression after LASIK. Shojaei and colleagues demonstrated that timolol 0.5% twice daily can reverse myopic regression by approximately 0.6 D, whereas in the control eyes, myopia progressed by approximately 0.3 D. The effect of the timolol was statistically significant in the low and moderate myopia groups (up to but not over -10 D). The IOP declined from 13 mm Hg to 10 mm Hg during the 6 months of timolol treatment and reverted back to 13 mm Hg after it was stopped. The IOP did not change in the control group. They also showed that the refractions remained stable for 6 months after timolol was stopped.
The investigators measured corneal thickness, which did not differ between the 2 groups at any time in the study. However, they did not measure anterior or posterior corneal curvature. Therefore, that the reduced IOP led to a change in corneal curvature and thus reduced refractive regression can only be assumed. Why didn't the refractive regression continue after the timolol was discontinued and the IOP returned to baseline? The investigators postulate that by that time corneal healing had occurred, which strengthened the cornea enough so that it didn't bulge as much from the IOP. It would be helpful to confirm this possibility with corneal curvature measurements.
How can we use the results of this study in clinical practice? We should think about using timolol in eyes with mild-to-moderate degrees of refractive regression after myopic LASIK, especially if it is discovered in the first few months of the LASIK procedure. Timolol treatment probably won't work as well in more myopic eyes with higher degrees of refractive regression. In those eyes, surgical enhancement should be considered when the refraction is stable.
This raises the question of whether other IOP-lowering medications would work as effectively as timolol, which has occasional systemic side effects, as well as whether timolol (or another IOP-lowering medication) would work for refractive regression after myopic surface ablation, such as photorefractive keratectomy or epi-LASIK. These are excellent questions for future studies.
Abstract