Advances in corneal and refractive surgery have helped optimize LASIK and transplantation procedures.
Keratomileusis, meaning to carve the cornea, was the precursor to LASIK. During keratomileusis, cryolathing was performed. A microkeratome was used to cut a cap that ranged in thickness from 320 to more than 420 µm, much thicker than in LASIK. Jose Barraquer, MD, did calculations by hand to determine the cryolathe settings. This calculation, designed to prevent tissue loss, was difficult because during the procedure, both the cutting tool and the head that the cornea was on were shrinking as they cooled, which required perfect timing, according to Dr. Price, who is in private practice in Indianapolis.
LASIK, the new method of "carving" the cornea, is much more precise and allows very accurate refractions, he noted. The sculpting is done in the bed and not the flap, no sutures are used, and the procedure is done using topical anesthesia.
Optimizing LASIK safety
LASIK has become safer over the years in flap creation and in prevention of dry eye and glare and halos postoperatively.
"The flaps were the biggest safety problem associated with the early LASIK cases," Dr. Price said.
Since 1995, LASIK flaps have more consistent depths and safety profiles because of the use of newer microkeratomes and the femtosecond laser. The femtosecond laser allows creation of reverse side cuts that might make the wound more stable and the flaps stick more tightly compared with flaps created with microkeratomes, according to Dr. Price.
LASIK surgeons are more aware now of the effects of LASIK regarding development of dry eye. The condition is now treated more aggressively with topical cyclosporine (Restasis, Allergan), dietary supplements, and addressing blepharitis.
Glare and halos are now rather uncommon complaints after LASIK, Dr. Price noted.
"This has resulted from better treatment profiles," he said, noting the progression from wider treatment zones to blended zones, and on to wavefront-guided and wavefront-optimized treatments.
Dr. Price mentioned research by Steven Schallhorn, MD, that showed that the development of glare and halos is not associated with pupil size, even out to 9 mm, or with spherical or astigmatic correction.
"The development of glare and halos was correlated only with uncorrected visual acuity," Dr. Price said. "To reduce glare and halos further, we must provide patients with the best, most natural vision."