Peripheral MMC application considered worthwhile

Dubai, United Arab Emirates-The use of topical peripheral annular application of mitomycin-C (MMC) 0.02% for 2 minutes is safe and effective in preventing corneal scarring after PRK with more predictable refractive outcomes. In addition, it decreases the potential for side effects, especially damage to the corneal endothelium, associated with topical MMC disc application and central corneal exposure to MMC, according to Elias F. Jarade, MD.

Despite the popularity of LASIK, PRK is still used to treat patients with thin corneas, basement membrane dystrophy, as well as those with low-to-moderate myopia, he explained. However, PRK can be associated with subepithelial haze and corneal scarring, he said.

"Reducing the development of subepithelial haze and corneal scarring associated with PRK is of great importance," said Dr. Jarade, in private practice at the International Medical Center, Dubai, United Arab Emirates. "Disc application of different concentrations of MMC to the center of the cornea was associated with reduced formation of haze and scarring."

"The safety of MMC must be addressed whenever it is applied to the center of the cornea," Dr. Jarade said.

He and his colleagues conducted a study in patients with thin corneas and low-to- moderate myopia to assess the safety and efficacy of topical peripheral annular application of MMC 0.02% on filter paper soaked with the drug to prevent scarring after PRK.

The study was prospective in nature and included 21 eyes. Twelve eyes of six patients were randomly assigned to the MMC group that underwent PRK and received topical peripheral annular application of MMC 0.02% for 2 minutes, and nine eyes of five patients were randomly assigned to the control group that underwent PRK only. Mechanical debridement of the corneal epithelium was performed with a surgical blade, and the Nidek EC-5000 excimer laser was used in all eyes.

Ring of MMC

In the MMC group, an 8-mm filter paper ring soaked with the drug was applied to the mid-peripheral cornea for 2 minutes, and the cornea was flushed thoroughly afterward with balanced salt solution. All eyes received a bandage soft contact lens and topical fluorometholone 0.1% for at least 3 days after surgery until re-epithelialization occurred and then this was replaced with topical prednisolone 1% for at least 1 month.

Preoperatively, both groups had similar mean spherical refractive errors, corneal thickness, radius of curvature, and best-corrected visual acuity (BCVA).

"Postoperatively, all 12 eyes in the MMC group were within ±0.5 D of the target refraction compared with only five of the nine eyes in the control group," Dr. Jarade said. "In addition, the postoperative uncorrected visual acuity (UCVA) was virtually the same as the preoperative BCVA in the MMC group (0.92 and 0.90, respectively) but in the control group, the postoperative UCVA and BCVA were only 0.66 and 0.77, respectively, versus preoperative BCVA of 0.91."

Epithelial regeneration was complete by the third postoperative day in all eyes. No haze developed in any eyes in the MMC group. Seven eyes in the control group developed haze; four eyes had +1 haze and three eyes +2 haze.

Superficial punctate keratitis developed in four eyes in the control group, and one eye in the MMC group developed filamentary keratopathy. One patient in the MMC group had bilateral reactivation of subepithelial infiltrates in the periphery of the cornea (old adenoviral keratoconjunctivitis), but this was managed successfully with topical steroid treatment.

Three eyes in the MMC group gained one or more lines of BCVA. Six of the nine eyes in the control group lost one or more lines of BCVA.

"The use of topical peripheral annular application of MMC 0.02% for 2 minutes was safe and effective in preventing corneal scarring after PRK with more predictable refractive outcomes," Dr. Jarade said.