Innovations move refractive surgery along path back to the surface

As the evolution in refractive surgery continues, surgeons can expect to see the journey continuing back to the surface—aided by new strategies to improve the outcomes of sub-Bowman's keratomileusis (SBK) and PRK, said John Marshall, PhD, in his keynote address at Refractive Surgery Subspecialty Day.

SBK, involving creation of a very superficial flap using a femtosecond laser, was introduced to provide the benefits of both LASIK and PRK. Since creation of the very thin flap minimally reduces the strength of the cornea, SBK is expected to provide the biomechanical stability of PRK, but like LASIK, without the pain and haze that are sequelae of post-PRK wound healing, he said.

Looking to the future, Dr. Marshall suggested biomechanical stability after SBK can be further improved by changing the edge angle of the flap.

"Making the edge angle more oblique makes the flap stronger," said Dr. Marshall, head of the department of ophthalmology, Kings College, London.

Recognizing that wound healing is a limiting variable for PRK, Dr. Marshall suggested the surface ablation procedure will be improved by pharmacologic modulation of that process. Possible strategies include use of the simple sugar, mannose 6-phosphate, and aptamer technology.

"Studies from our group show that mannose 6-phosphate, which blocks receptor sites on keratocytes, is effective in preventing haze in animal models," Dr. Marshall said. "In addition, we have found that aptamers selectively differentiating between activated and latent keratocytes can be used for targeted wound healing control."