Effect of Timolol on Refractive Outcomes in Eyes With Myopic Regression After Laser In Situ Keratomileusis: A Prospective Randomized Clinical Trial

We perused with great interest the randomized controlled trial by Shojaei and associates, which studied the effect of timolol eye drops in refractive outcomes in eyes with myopic regression after laser in situ keratomileusis (LASIK). In this trial, the authors compared the outcomes of treating patients presenting with myopic regression following LASIK with timolol eye drops instilled twice a day to treatment by instilling artificial tear drops in an identical regime as placebo. The spherical equivalent was significantly better in the timolol (treatment) arm 6 months after treatment, and also 6 months after discontinuation of treatment ( P < .001 for both comparisons). Based on these results, the authors concluded that instillation of timolol eye drops is effective for the treatment of myopic regression after LASIK and its effect seems to last for at least 6 months after discontinuation. The study design and statistical analysis were appropriate, but we do have the following observations to make.

There are some typographical errors in the article; for example, in Table 3 spherical equivalent before treatment in Placebo group should have been −1.57 ± 0.67.

In Table 5 (and also at various places in the results and discussion sections), uncorrected distance visual acuity (UDVA) in logMAR is represented in negative values. It is well known that in the logMAR system a more negative value indicates a better visual acuity. Applying this knowledge to the table in question, the visual acuity is consistently better in the placebo arm. Also, within the timolol arm the UDVA before treatment is more negative (better) than 3, 6, and 12 months after treatment.

The method of refraction has not been mentioned. It would also be pertinent to know if all the refractions were done by a single optometrist.

Though the authors have mentioned that there were no side effects observed in the study, the exclusion criteria do not account for respiratory or cardiovascular diseases, where timolol eye drops should be used with caution. The use of timolol has been associated with behavioral changes, which was not mentioned in the study.

The underlying hypothesis that myopic regression post LASIK results from forward shift of the posterior cornea should have been studied and documented by serial elevation–based corneal topography on follow-up visits. The efficacy of timolol in arresting or resolving these topographic changes and a comparative analysis of the same between the 2 arms would have added significant weight to the presented refraction data.

Some patients in either arm might have had early corneal ectasia after LASIK and could have been differentiated from regression purely on corneal topography.

Timolol has been reported to prevent the progression of post-LASIK ectasia. Therefore the fact that the best-corrected distance vision in the placebo group was less than 20/20 could be an outcome influenced by this potential confounder.

To conclude, we opine that though the study was very well designed, attention to these details would have made the results more robust.

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Jan 9, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Effect of Timolol on Refractive Outcomes in Eyes With Myopic Regression After Laser In Situ Keratomileusis: A Prospective Randomized Clinical Trial

Full access? Get Clinical Tree

Get Clinical Tree app for offline access