U.S. Air Force study: Balance weighs in favor of LASIK

October 1, 2008

Evaluation of low contrast sensitivity outcomes after wavefront-guided refractive surgery in U.S. Air Force aviators shows quality of vision returns much faster after LASIK compared with PRK.

Key Points

San Antonio-A study evaluating quality of vision outcomes in U.S. Air Force (USAF) aviators undergoing wavefront-guided refractive surgery suggests that LASIK provides the combat edge in vision compared with PRK.

"The findings affirm that LASIK is safe and effective in USAF aviators and suggests that the safety and efficacy of this procedure may be enhanced by flap creation with femtosecond laser technology, although this latter point is being examined by ongoing studies," said Maj. Vasudha Panday, MD, USAF Medical Corps, Wilford Hall USAF Medical Center, Lackland Air Force Base, San Antonio.

"The most interesting finding was that low contrast sensitivity recovered much quicker after custom LASIK than it did in aviators who underwent custom PRK," he continued.

"The refractive surgery community is pretty well convinced that regardless of the procedure performed, contemporary laser vision correction surgery provides excellent long-term vision outcomes," he said. "However, it was surprising to see in this study that quality of vision after custom surgery, measured by low contrast (5%) sensitivity, returned much faster after LASIK than after PRK. When rapid return of high-quality vision is important, LASIK appears hard to beat."

The study included the first 55 eyes of USAF aviators who underwent LASIK and showed excellent uncorrected visual acuity (UCVA). At 1 month after surgery, mean UCVA was about 20/16, and no significant difference was observed between preoperative and postoperative low contrast sensitivity, 20/35 versus 20/37, respectively. At 6 months, mean UCVA was unchanged, mean best spectacle-corrected visual acuity was 20/14.9, and mean low contrast sensitivity had improved slightly to 20/35.

Comparison of low contrast sensitivity in the 55 LASIK eyes with a group of 422 eyes that underwent wavefront-guided PRK showed slightly better performance in the PRK group preoperatively, which was attributable to the lower refractive error in the PRK eyes compared with the LASIK group. In the LASIK eyes, low contrast sensitivity was better than the preoperative level by 3 months after surgery, whereas it took until 6 months after surgery for the PRK eyes to reach that outcome.

The only complication recorded after LASIK was interface debris in one eye. Otherwise, no intraoperative or postoperative events were recorded, including no cases of buttonholes or free caps, microstriae, slipped or dislocated flaps, diffuse lamellar keratitis, or epithelial ingrowth.

"There also were no subjective quality-of-vision complaints, although this finding must be taken with a grain of salt because an aviator who complains about vision can be grounded from flying," noted Dr. Panday.

Each branch of the U.S. Armed Forces, he said, has its own policy regarding refractive surgery. In the USAF, the first refractive surgery vision summit was held in 1985 to review the appropriateness of radial keratotomy. The expert panel decided not to allow that incisional procedure.

The first excimer laser for refractive surgery in USAF personnel was purchased in 1996, and in 1997, the first PRK procedure was performed. The USAF PRK program was established in 2001.

"LASIK was not allowed for USAF aviators until 2005. It was restricted to those who flew at cabin altitudes below 14,000 feet. In 2007, LASIK was approved for all USAF personnel, including for aviators flying high-performance aircraft. However, all USAF pilots and boom operators can only be operated on at Wilford Hall Medical Center," Dr. Panday explained.

"The USAF was the first armed service branch to allow LASIK in high-performance aircraft pilots who operate under extreme environmental conditions. The approval was granted based on consideration of maturation of the technology; the introduction of the femtosecond laser, which was thought to be superior to mechanical microkeratomes for flap creation; and the accumulated anecdotal evidence showing pilots performed well after the surgery along with the excellent research performed by the U.S. Navy at San Diego," noted Dr. Reilly.

"We wanted to be able to offer the full range of corneal refractive surgery to our personnel. However, after lifting the ban on LASIK, we proceeded in a cautious way to implement this program for our aviators," he said.

Although use of the femtosecond laser is preferred for flap creation, Dr. Reilly said, any microkeratome is allowed. Surface treatment can be performed in any Department of Defense facility but is restricted to eyes with mean spherical equivalent less than –5.50 D. LASIK in Air Force pilots is restricted to Wilford Hall Air Force Medical Center at this time.

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