A potential new endpoint for understanding post-LASIK outcomes

October 28, 2014

Corneal epithelial thickness has been found to remodel and change significantly after femto-LASIK, according to the findings of a prospective study conducted under the direction of A. John Kanellopoulos, MD, and colleagues.

New York-Corneal epithelial thickness has been found to remodel and change significantly after femto-LASIK, according to the findings of a prospective study conducted under the direction of A. John Kanellopoulos, MD, and colleagues.

Specifically, corneal epithelial thickness increases in the mid-periphery, just inside the ablation zone, and the magnitude of change correlates with the amount of myopic correction.

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The research was conducted jointly at the Laservision.gr Research and Clinical Institute, Athens, Greece, and the Department of Ophthalmology, NYU Langmore Medical School, New York, NY. It was published [J Refract Surg. 2014;30(3):16671] and presented by David Sackel, MD, who was senior resident, Department of Ophthalmology, NYU Langmore Medical Center.

“These findings are compelling and should be taken into account when evaluating quality of vision and mesopic and scotopic issues, as the epithelial changes may affect particularly those pupillary values,” Dr. Kanellopoulos said.

“In addition, evaluation of epithelial thickness may become an important additional measure for assessing refractive outcomes, their stability, and potential need for enhancement, particularly considering that high deviation from usual patterns in high myopic corrections that more commonly need enhancements,” Dr. Sackel said.

 

The study included 61 consecutive patients (myopia range, -8.50 to -1.00 D, cylinder range, 0.00 to -3.25 D) who underwent evaluation of 3-dimensional epithelial thickness mapping with an anterior segment, spectral-domain optical coherence tomography (OCT) platform (RtVue, Optovue) preoperatively and at 1 day, 1 week, 1 month, and 1 year after LASIK.

Mean epithelial thickness values were calculated for the central 2-mm region, mid-peripherally at the 5-mm ring area, and averaged over the central 6-mm area.

There was a mean decrease in all three epithelial thickness measurements on the first day postoperatively, but evidence of epithelial remodeling by 1 week. At 1 month, all three values had increased significantly from baseline with the change being greater in the mid-periphery than centrally. The changes from baseline were similar at 1 year.

Linear regression analysis showed a good correlation between the degree of myopic correction and increase in epithelial thickness (r = 0.831).

“Existing reports show that central epithelial thickness increased after LASIK using a mechanical microkeratome, and a lenticular shape of the change has also been shown with scanning ultrasound,” Dr. Sackel said. “We believe our study is more comprehensive and unique in many ways as it evaluates changes after femtosecond laser-assisted LASIK in a larger patient population with serial measurements during longer follow-up and using spectral domain OCT to quantitate 3-dimensional corneal epithelial thickness changes.

“Further research is needed to confirm these changes and understand their potential relevance, but we believe they may correspond with early, interim, and late acuity and quality of vision findings in patients after myopic LASIK,” he added.

 

Dr. Sackel noted that findings from another study using spectral-domain OCT showed greater epithelial thickness in eyes with dry eye compared with normal controls. Based on that information, the investigators are postulating that measurement of epithelial thickness after LASIK may be used as an objective, simple and user-friendly tool in the diagnosis and management of LASIK-related dry eye.