Laser assisted in-situ- Keratomileusis (LASIK), the most commonly performed surgery for refractive correction provides good refractive correction over a wide range of refractive errors with predictable outcomes. This is largely attributable to improvisations in ablation parameters, nomograms and sophisticated centration and eye tracking systems. But still, about 20-30 % patients experience regression or gradual loss of the refractive correction over time. Various factors such as high pre-operative spherical equivalent, thinner corneas, raised postoperative intraocular pressure, under-correction and older age of the patient have been reported to increase the risk of myopic regression. While re-surgery is an option, the authors wanted to explore other non-surgical therapeutic modalities for the same.
As intraocular pressure is a modifiable factor, it has been suggested that topical IOP lowering agents suggest as timolol maleate, a non-selective β blocker, can improve myopic regression after LASIK. The purpose of this study was to evaluate the effect of Timolol Maleate (0.5%) in the treatment of myopic regression post LASIK.
In this prospective interventional study, patients who presented with regression after undergoing uneventful myopic LASIK by a single surgeon were included . Regression was defined as uncorrected distance visual acuity (UDVA) of 20/20 at final follow-up post LASIK, but UDVA loss of two lines, correctable with residual refraction 3 months or more post-operatively. Only those patients who had finished their post-operative course of topical steroids were included in the study. Patients with history of corneal ectasia, keratoconus, glaucoma, cataract, refractive surgery re-treatment, previous ocular surgery other than LASIK, posterior segment disorders, pregnancy or breastfeeding were excluded.
The enrolled patients were prescribed Timolol Maleate (0.5%) eyedrops twice daily. They were followed up every month till 3 months on Timolol (0.5%) eyedrops and at 6 months post-treatment. UDVA, Refraction, IOP measurement, Central Corneal Thickness (CCT) measurement, Topography (Anterior and Posterior keratometry) were performed at every subsequent follow-up. The primary outcome measure was change in Mean Spherical Equivalent (SE) at 6 months after completion of treatment. Secondary outcome measures were changes in Central Corneal Thickness, IOP and Keratometry (Anterior and Posterior curvatures) at 6 months following completion of treatment.
Twenty-nine eyes of 15 patients were enrolled in the study. The results were as follows
- Mean pre-LASIK spherical equivalent (SE) was around – 7.5D
- Mean regression spherical equivalent was around -1D
- There was a significant decrease in mean SE from presentation up to 6 months follow-up
- Posterior corneal curvature changed significantly over treatment period but change in anterior corneal curvature was not significant
The study thus showed that topical Timolol maleate (0.5%) was effective in treating post LASIK regression. The keratometry findings in the study demonstrated significant changes in the curvature of the posterior surface of the cornea indicating that IOP reduction induced a backward shift and flattening of the cornea with resultant reduction of corneal refractive power.
"Topical therapy with timolol maleate (0.5%) eyedrops can be used as a treatment modality for treating regression with significant comfort, compliance and safety so that all patients presenting with regression do not need laser re- treatment which has its own pitfalls. However, further studies are necessary to evaluate whether the regression will reverse after discontinuation of the eye drops and also to decide the duration of therapy required to prevent such recurrence." conclude the authors.
For further reading, click on the link:
https://www.ijo.in/article.asp?issn=0301-4738;year=2020;volume=68;issue=12;spage=2990;epage=2994;aulast=Singh
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