LASIK with IntraLase now being studied in aviators

After studies confirm the procedure’s safety, efficacy, and recovery time, aviators have now been treated with LASIK instead of PRK

Marine Capt. Michael Oginsky was the first Naval aviator to undergo wavefront guided LASIK with the femtosecond laser.


Dr. Schallhorn examines Capt. Oginsky’s eyes before he undergoes LASIK.

Source: Steve Schallhorn, M.D.

Late last year, aviators became the last group of Department of Defense employees to be eligible for and undergo LASIK surgery. Until November, aviators in the U.S. Navy received only PRK, but a new Bureau of Naval Medicine project is underway after numerous clinical trials on non-aviation personnel. According to Capt. Steven Schallhorn, M.D., director of cornea and refractive surgery, Naval Medical Center, San Diego, aviators will be studied who have corrective surgery with CustomVue (Advanced Medical Optics, AMO, Santa Ana, Calif.) and IntraLase (now part of AMO), what he calls the “best of the best.”
Currently, the Naval Medical Center in San Diego is the only DoD facility to offer LASIK with IntraLase, but the IntraLase is expected to become available to other Navy refractive surgery centers shortly, Dr. Schallhorn said, who performed the first aviator surgery in November.
“This procedure on an aviator is a milestone for refractive surgery, both for the military and the community in general,” Dr. Schallhorn said. Surface ablation (PRK, LASEK, epi-LASIK) is performed much more often than LASIK on military personnel, but Dr. Schallhorn often prefers LASIK.
“I’d say that the optimal mix in the military will eventually be 20%/80%, PRK/LASIK,” he said. Dr. Schallhorn has been involved in many clinical trials evaluating LASIK on military personnel.
“We’ve performed LASIK on thousands of patients. About seven years ago, we did a large LASIK study comparing four different excimer lasers,” he said.
Two primary reasons have prevented LASIK from being performed on aviators until this point—concerns about the flap stability and the quality of vision with conventional (standard) LASIK.
“For instance,” he said. “An ejection from a high speed aircraft is going to subject the aviator to a significant wind blast.”
Other issues present for aviators include “dry air conditions” in the cockpit, hypobaria, and particulate matter in the air, he said.
“Over the past eight years, we’ve analyzed many flap concerns from an aeromedical standpoint,” Dr. Schallhorn said. “We studied the effect of wind blast on the stability of the LASIK flap and many other environmental issues. The conclusion is that there are no ‘show stoppers’ related to aviation specific environmental issues. The LASIK flap should be no more prone to problems than with other military occupations.”
He added other studies found no changes occurred in visual acuity or contrast sensitivity in LASIK-induced flaps when compared to normal controls after being exposed to environmental conditions an aviator might find.

Quality of vision

The second major concern before moving forward with LASIK in aviators was the quality of vision from the procedure itself, Dr. Schallhorn said.
“We looked at quality of vision issues for all types of refractive surgery; it has been one of our primary objectives over the past 12 years,” he said.
In 2002, the Navy was close to evaluating LASIK in aviators because most environmental concerns of the flap had been addressed, Dr. Schallhorn said.
“The aviator is a high-valued asset and represents a significant investment to train properly. We need to exercise a high level of due diligence and careful analysis to uncover potential disabling complications unique to this group,” Dr. Schallhorn said.
In 2002, the military undertook a large retrospective analysis to compare the quality of vision in “thousands of eyes” of non-aviators who had undergone conventional LASIK or conventional PRK.
“The comparison showed that conventional LASIK had an average loss of contrast acuity after surgery which did not resolve over time. This was unlike conventional PRK which had a mean loss in the early postop time period but returned to preoperative levels by 3 months. The difference in quality of vision was also apparent in subjective symptoms of glare and halos after surgery. PRK patients tended to have less symptoms.”
As a result, PRK remained the procedure of choice in aviators, “but it did accelerate our interest in ways to improve overall quality of vision with LASIK,” he said, which led to “many studies” to look at issues such as flap creation and wavefront-guided technology.
One such study, a randomized, prospective study spearheaded by David Tanzer, M.D., Naval Medical Center, San Diego, compared mechanical microkeratomes with femtosecond laser flap creation in almost 800 eyes. Another series of studies evaluated wavefront-guided technology.
“We first used aberrometers to study higher order aberrations in 1999,” Dr. Schallhorn said. With it, the researchers discovered the types of aberrations that were typically induced by LASIK or PRK. During one study, the researchers took the aberrometer up to Pikes Peak (14,000 ft. peak in Colorado) to compare sea level results with high altitude results. Later studies of wavefront-guided LASIK determined that the technology overcame the shortcomings of conventional surgery, namely that the quality of vision was significantly better with wavefront guided surgery than with conventional LASIK.
Studies also concluded that a femtosecond laser was “better than a mechanical microkeratome,” Dr. Schallhorn said. “The femtosecond flap is more consistent then mechanical microkeratomes. Femtosecond lasers also afford the patient significantly faster visual recovery.”
In terms of quality of vision, the femtosecond laser had improved contrast sensitivity compared to mechanical microkeratomes. “The mechanical microkeratomes were closing the difference between the two technologies at the three-month follow-up, but the femtosecond laser still offered significantly better quality of vision,” Dr. Schallhorn said.
The results were a “big nod for the femtosecond laser. The safety profile was better as well,” he said. “Not that it’s risk-free, but the femtosecond laser results were consistently better than a mechanical microkeratome.”
Implications
Downsides to the femtosecond laser include its price, but once lost workdays in the aviation community were factored, the femtosecond laser still appeared to be the better technology.
“Our conclusion was that there were no ‘show stopper’ aeronautical issues related to the femtosecond flap. The best flap technique is to use the femtosecond laser and the best ablation profile is wavefront-guided technology,” Dr. Schallhorn said.
“In 10 years, we’ll look back and see that it was an easy decision to utilize the femtosecond laser,” he said.
The Navy is in the midst of another study, comparing surface ablation to wavefront-guided LASIK with the IntraLase femtosecond laser. Results are not yet complete, but early data suggests the two procedures are essentially equivalent, with LASIK providing a much faster visual recovery, Dr. Schallhorn said.
For aviators, the faster visual recovery times are key, Dr. Schallhorn said. With a surface procedure, the aviator has to wait three months before returning to the cockpit. With wavefront-guided LASIK, it is currently one month.
“With the additional technology of the IntraLase, visual recovery may be as short as one week post-op, but we’re confident it will be no longer than four weeks,” he said.
To date, pilots are still not eligible for LASIK.
“We won’t be doing LASIK on pilots for a while, not until additional studies are completed. LASIK was performed on a small number of non-pilot aircrew as part of an initial trial series,” Dr. Schallhorn said, who added that currently he and Dr. Tanzer were the two surgeons in this series.
“We want to offer military personnel the best. The best costs more, and we have decided to embrace the technology and offer the best currently available. Over 90% of the armed forces are not aviators, and they too would be eligible for the wavefront-guided LASIK with IntraLase,” Dr. Schallhorn said.
Finding an acceptable candidate for the first group required specific criteria to be met, Dr. Schallhorn said. Aside from the medical requirements (refractive error within the approved treatment range), militarily the requirement mandated a flight officer who could be on the ‘reserve’ list for 30 days with no impact on his/her squadron. Marine Capt. Michael Oginsky fit both requirement parameters, and underwent bilateral LASIK in November 2006.
“I was definitely seeing better right away, and within four hours my vision was 20/20,” Mr. Oginsky said. After 24 hours, his vision improved beyond 20/20. Additionally, at the one-week follow-up, the surgical flaps had sealed.

Editors’ note: Dr. Schallhorn has no financial interests related to his comments.

Contact Information
Schallhorn: 619-920-9031, scschallhorn@yahoo.com