Epi-LASIK yields similar outcomes with or without flap

December 15, 2008

Epi-LASIK is a laser vision correction procedure that is a variation of PRK. Both surgeries are considered "surface" ablation procedures because the excimer laser treatment takes place near the surface of the cornea. No LASIK-style flap containing both the superficial corneal layer (the epithelium) and deeper corneal tissue (the stroma) is involved.

But in epi-LASIK, rather than destroying a central zone of epithelium to prepare the eye for excimer laser treatment, an attempt is made to preserve it — both to relieve early post-operative discomfort and to speed healing (re-epithelialization) of the cornea after surgery.

The epithelial "flap"

In the first step of epi-LASIK, a hand-held surgical tool called an epithelial separator is used to remove a thin sheet of epithelial cells from the surface of the eye. Because this "flap" of epithelium is so thin (less than 100 microns), maintaining its integrity and repositioning it intact on the eye after laser treatment is highly challenging.

In many cases, the epithelium cannot be successfully replaced (or the surgeon chooses not to replace it) and it is discarded. In such instances, the post-operative epi-LASIK eye resembles a post-op PRK eye — the residual stromal bed of the cornea is completely exposed after the excimer laser treatment.

Flap on, flap off: Does it matter? In a study published in the December 2008 issue of Ophthalmology, researchers investigated whether a difference exists in corneal healing or visual outcomes when the epithelial sheet created in epi-LASIK surgery is repositioned or discarded.

The study included 112 eyes of 56 patients. All eyes had low to moderate myopia (nearsightedness). The average age of patients in the study was 26.6 years.

Standard epi-LASIK (epithelium sheet repositioned) was performed on one eye of each patient and "off-flap" epi-LASIK (epithelium discarded) was performed on the other eye. Epithelial healing time, visual acuity and refractive endpoints were measured in follow-up visits for 12 months.

Epi-LASIK study: Results

Among the results of the study:

Average epithelial healing time was essentially the same for the two groups (4.76 days for the standard epi-LASIK procedure, 4.54 days for the off-flap procedure).
At one month after surgery, 21 percent of the standard epi-LASIK eyes and 20 percent of the off-flap eyes had gained one or two lines of best-corrected visual acuity (BCVA), compared to their vision with glasses or contact lenses prior to surgery.
At one month post-op, 25 percent of the standard epi-LASIK eyes and 20 percent of the off-flap eyes had lost one or two lines of BCVA. (But BCVA in both groups improved over time.)
At one year after surgery, 90 percent of both the standard epi-LASIK eyes and the off-flap eyes were within +/- 0.50 diopters (D) of the targeted refraction.
At one year post-op, 100 percent of the standard epi-LASIK eyes and 95 percent of the off-flap eyes were within +/- 1.00 D of the intended refraction.
Throughout the 12-month follow-up period, there were no significant differences in higher-order aberrations among the two groups.

Epi-LASIK study: Conclusions

Based on these findings, the study authors concluded, "Epi-LASIK and off-flap epi-LASIK had equal refractive and visual results, and they did not differ regarding their early post-operative course."