Wavefront-optimized PRK successful in Air Force personnel
Speed, accuracy and efficacy are three reasons why the wavefront-optimized laser is a solid performer.
Refractive surgery is not cosmetic surgery, although the desire to be rid of spectacles and contact lenses may play a part in patient motivation. In the military, refractive surgery is limited to PRK and LASIK. We are not allowed to perform phakic IOL implantation, clear lens exchange or conductive keratoplasty on active duty Air Force personnel.
The Air Force allows LASIK in high-G-force aircraft personnel, including fighter pilots. Service members looking to undergo the procedure must first obtain clearance from their commanding officer and be prepared to be nondeployable for 1 month after LASIK and 4 months after PRK. These limitations can affect which type of refractive procedure the patient prefers. Also unique to the Air Force is a limit on the upper levels of hyperopia.
Eighty-two percent of Air Force personnel opt to undergo PRK. PRK has a long track record in the military, so most personnel request the procedure by name, and the successful outcomes we have had in the past with PRK are likely why it is still the most requested procedure.
Wilford Hall Medical Center at Lackland Air Force Base in Texas is one of seven Air Force centers in the U.S. We received a wavefront-optimized laser about 18 months ago and began using this platform to perform PRK on our Air Force personnel. This is an off-label use of the laser platform. To date, I have used it on 1,500 eyes and have 6 months of follow-up data on 838 eyes of 419 patients. We also recently began using the wavefront-guided platform on this laser but only have preliminary results out to about 1 month.
In both LASIK and PRK, we have found that the wavefront versions performed better than standard ablations. There are several improvements with the wavefront-optimized platform, not the least of which is the speed of the platform, enabling a very short actual treatment time averaging about 5 to 20 seconds. Beyond that, the ability to personalize a treatment to a particular patients corneal curvature cannot be underestimated. That is one aspect of the wavefront-optimized laser I have thoroughly enjoyed.
A secondary point is the systems ability to let me plan a treatment on the laptop and then connect the laptop directly to the laser. As busy as we are in our daily clinical routines, the ability to plan a treatment strategy in the comfort and quiet of my own office has been an unexpected bonus.
We have data on 838 eyes with 6 months of follow-up. We accepted patients with refractive errors between 8.75 D and +4 D, with cylinder up to 3.75 D. All patients had opted to undergo PRK, and the ages ranged from 21 years to 60 years. In my hands, there is no nomogram adjustment needed for those with less than 4 D and under 2 D cylinder. We determined the optimal treatment method based on preop refraction and wavefront higher-order aberration root-mean-square to determine whether a wavefront-optimized or -guided ablation would be best.
As with most refractive surgery, patient selection is important. We typically find that those with 0.3 root-mean-square or higher would benefit more from wavefront-guided treatments. Under 0.3 root-mean-square, the wavefront-optimized treatment seems to provide great outcomes.
For military personnel, when talking about postop quality of life, low-contrast vision is evaluated (think of a gray airplane flying in a gray sky). Previous wavefront-guided outcomes showed low-contrast vision improving over time, and the same thing is found with the wavefront-optimized laser.
Images: Reilly C
When we evaluated the percentage of eyes obtaining 20/20 vision, 93% of those who had PRK achieved 20/20 by 6 months. We know from our data that PRK tends to improve over time, so I expect those visual results to continue improving. We are still comparing and contrasting the outcomes of wavefront-optimized and -guided PRK, but there does not seem to be any difference between the two groups in terms of speed of recovery. The Air Forces results with wavefront-guided PRK prove the technique to be a solid performer. Although my personal experience with wavefront-guided PRK on the optimized laser system is encouraging, it is too early for any of the patients to have achieved refractive stability.
For our military personnel, when we talk about postop quality of life, we evaluate low-contrast vision (think of a gray airplane flying in a gray sky; see photos). We know our previous wavefront-guided outcomes showed low-contrast vision improving over time, and we are now finding the same thing with the wavefront-optimized laser. The last thing we want is to give someone 20/20 vision but have their contrast sensitivity negatively impacted.
None of our patients lost more than two lines, which is within the realm of standard PRK. For those with follow-up out to 1 year, we have no reports of corneal haze with this laser platform. We do not use prophylactic mitomycin C, so to have no haze at this point has been reassuring. Historically, the Air Force has had low levels of reported corneal haze, so we do not feel it is necessary to use prophylactic MMC.
By 6 months, we have found our visual outcomes are basically the same, regardless of whether we perform LASIK or PRK on the wavefront-optimized laser platforms. We have been pleased with our outcomes with wavefront PRK so far, although we recognize LASIK does offer a faster speed of visual recovery. With more than 1 year of follow-up on a majority of our patients, we have not had to perform any enhancements on those who underwent PRK on the wavefront-optimized laser. Not everyone is at 20/15, but no one has asked for an enhancement. About 50% of our patients have achieved 20/15 at the 1-year mark.
One aspect to consider when planning surgical treatments on the wavefront-optimized laser is that the platform requires a lot fewer data points than does wavefront-guided PRK. In my opinion, the time it takes to develop a surgical plan is also condensed. Having a slit lamp on the device itself can be a useful tool when your visualization is hampered.
Results achieved in military personnel may be unique. Our average age for PRK is 32 years, so it may be unfair to compare our exemplary results to those of physicians serving nonmilitary patients.
Our outcomes with wavefront-optimized PRK really are the perfect storm of great technology in great hands with great patients. With almost 30% of all treatments today being PRK, we are working toward ensuring that the U.S. Food and Drug Administration approves this technology for surface ablation.
Disclosure: The opinions stated in this article do not necessarily reflect those of the Department of Defense or of the United States Air Force.
- Charles Chaz Reilly, Lt. Col., USAF, MC, FS, is the chair of the Department of Ophthalmology and consultant to the Air Force Surgeon General for refractive surgery at Lackland Air Force Base, Texas. He can be reached at firstname.lastname@example.org.