PRK with MMC effective for treating hyperopia after RK

Wavefront-guided PRK with mitomycin C (MMC) performed to enhance eyes that had undergone previous RK seems to be a safe and effective procedure, although there is a risk of moderate haze developing, said Douglas Koch, MD.

He drew his conclusions from a four-center study in which custom laser vision correction (CustomVue, Advanced Medical Optics) was used to perform enhancements in all eyes.

"We know that hyperopic shift is a common problem after RK, that is, 43% of eyes have a shift of 1 D or more," said Dr. Koch, of the Department of Ophthalmology, Baylor College of Medicine, Houston. "LASIK procedures carry the risk of separation of the incision, and PRK is associated with the development of haze. We investigated the use of MMC with PRK."

Hyperopia in the 28 study patients ranged from +1.79 to +4 D; 13 of the patients were followed for 12 months (mean, 11 months) after enhancement.

"Regarding efficacy, the postoperative visual acuity over the preoperative visual acuity, was 0.87," he said. "At the 6-month examination, 44% of the eyes had 20/20 vision, and at the 12-month examination, 62% of the eyes achieved that level of vision. This is fairly good. All eyes achieved 20/40 or better."

When the results were compared with conventional LASIK, Dr. Koch found that the data were below the target for normal eyes that had not had a prior surgery, that is, 70% of eyes that underwent conventional LASIK achieved 20/20 compared with 44% for the procedure under discussion.

Dr. Koch also indicated that the safety index was good, with a few patients having lost a line of vision and some patients gained a line or two of vision. The predictability of the procedure also was good, but not as good as what can be achieved with a standard ablation. The procedure was very stable at 12 months.

Haze is the big concern with this procedure, according to Dr. Koch.

Haze, the only complication, developed in six of the 28 eyes ranging from trace to 1 to 2+. The haze was not related to the amount of correction, but may be related to the length of the application of MMC, he said. MMC was applied for 15 seconds in five of the six eyes with haze and in one eye for 30 seconds.

"The preliminary data suggest that application of MMC for 15 seconds may not be adequate, and perhaps it should be longer," Dr. Koch said. "A study with more eyes and longer follow-up is needed."