challenging refractive cases
Exploring the limits of LASIK

Meeting calls new attention to LASIK research directions

Femtosecond laser corneal flap with a roster pattern to create a superior hinge
Source: Dimitri Azar, M.D.


Intra-op image of corneal stroma during excimer laser treatment after flap lift
Source : Dimitri Azar, M.D.


Laser ablation with the Allegretto and flap creation with the IntraLase
Source: Daniel S. Durrie, M.D

The Food and Drug Administration (FDA) Ophthalmic Devices Advisory Panel meeting regarding LASIK in April thrust the popular surgical procedure into the spotlight.
Although numerous studies have proven LASIK to be safe and effective, many believe it still can benefit from further research to bolster the procedure,
Previous studies have enabled surgeons to reduce night-vision problems such as glare and haloes, said Daniel S. Durrie, M.D., clinical professor of ophthalmology, University of Kansas, Overland Park. Research also has led to increased use of wavefront technology, making LASIK even more personalized to the patient’s visual needs.
Now, clinicians can turn their attention to issues such as managing dry eye, reducing ectasia, and testing LASIK’s limits in unique population groups, surgeons said.

Dry eye and LASIK

“The LASIK population by nature is drier because they can’t wear contacts,” Dr. Durrie said—but this is why they opted for surgery in place of contact lenses in the first place. “This is an area where we need to continue to evaluate patients pre-operatively with technology today and continue to develop better technology.”
Even though Dr. Durrie said not all surgeons believe that LASIK itself causes dry eye, many agree that the procedure can aggravate the ocular surface. As awareness of dry eye grows, research on the best ways to test patients for dry eye before surgery and a comparison of regimens that treat dry eye pre-op or post-op would benefit the field, surgeons said.
“There are a significant number of patients dissatisfied with dry-eye symptoms that don’t always show up on clinical tests. We’re learning to focus on this more,” said Richard L. Lindstrom, M.D., adjunct professor emeritus, University of Minnesota, Minneapolis.
Studies that demonstrate the value of using a medication like cyclosporine (ophthalmic emulsion, Restasis, Allergan, Irvine, Calif.) before and after surgery in all patients would assist in the goal to return patients back to normal visual function as soon as possible, said David Tanzer, M.D., director of the Navy refractive surgery program, San Diego.
Studies of pre-op treatment with omega-3 oils and better lid hygiene for better blepharitis patients would also expand the dry-eye/LASIK research arena, Dr. Durrie added.

Ectasia

The occurrence of post-LASIK ectasia deserves further study, Dr. Durrie believes. This research could cover patient screening and whether or not it is indeed ectasia that occurs after LASIK and not something else.
“”I think these [post-LASIK ectasia cases] are all keratoconus,” Dr. Durrie said. “I think it’s exceedingly rare that you would cause a normal cornea to get ectatic. I don’t think there’s evidence that we’re creating that, but I do think we’re not doing a good enough job to continue to screen for keratoconus patients and do good informed consent.”
This is where recent reports of corneal cross-linking, which stiffens the cornea, could help, Dr. Durrie said.
The development of genetic tests that would help determine patients at risk for keratoconus also could help steer suspect patients away from LASIK, he said.
Better ways to determine patients’ risk for post-op ectasia is an area ripe for future research, Dr. Durrie said. Although some recent studies in this area helped to generate thinking on this topic, Dr. Durrie would like to see more work.

LASIK in unique populations

The safety and efficacy of LASIK in a number of unique patient groups is another area that needs exploration, believes Steven C. Schallhorn, M.D., San Diego, and chief medical director, Optical Express, London. This includes both patient groups that were always assumed to be poor candidates for LASIK as well as groups that may have had trouble with LASIK originally but now may benefit from the surgery’s evolution.
Anecdotal evidence and smaller studies are showing that patients with certain stable disease conditions such as diabetes or well-controlled autoimmune conditions like rheumatoid arthritis and systemic lupus may be adequate LASIK candidates, Dr. Schallhorn said. However, because these patients generally have not been included in the FDA trials for the lasers, these conditions are listed as relative or absolute contraindications for LASIK.
“Maybe this contraindication isn’t a contraindication. Further study would be useful,” he said. “This is a group of patients who may benefit from LASIK but who are turned away.”
Other patients who deserve special study are quadriplegic and paraplegic patients who cannot wear contact lenses and need assistance wearing glasses, Dr. Schallhorn said. “We had a program in the Navy for patients with significant injuries to the arms and legs. LASIK can have a very positive impact on their quality of life,” he said.
Continuing study of LASIK in military patients, such as fighter pilots, will continue to show the procedure’s limits, said Drs. Schallhorn and Tanzer. “War fighters go into austere environments and hot, dirty places. We’re conscious of that and seek the most safe and effective procedure in the safest manner possible,” Dr. Tanzer said.
Dr. Tanzer reported at the FDA meeting some results from LASIK studies conducted in the Navy. For example, he said, of 250,000 procedures to date, to his knowledge, all but one patient were able to return to full-duty status. Some may say that LASIK has such stunning results in the military because patients tend to be younger; however, with an average surgical age of 32 in the Navy compared with 36 for the general population, the difference is not all that vast, Dr. Tanzer said.
Patients with extreme hyperopia and myopia are generally excluded from LASIK because of poor results—that said, the end visual results in these patients continues to be an area of interest. “Although these areas are understudied, you’d have to have new techniques and technology to make them viable for LASIK,” Dr. Schallhorn said. “The extreme levels have not been well studied. Given the small number of studies and outcomes, a lot of surgeons are not opting to do LASIK anymore in extreme patients.”
Dr. Lindstrom echoed those thoughts. “I almost never do +4 [in hyperopes] and in myopes, I rarely do over –10,” he said. His parameters are more conservative than what many lasers are approved for. In cases where patients want to take the surgical risk, he’ll operate on only one eye at a time to make sure patients are satisfied with the results.
More often, Dr. Lindstrom steers extreme myopes toward a phakic IOL and extreme hyperopes toward refractive lens exchange to ensure better results and higher patient satisfaction.
That said, some recent research is further exploring LASIK in extreme groups. In a study published this year in the Journal of Cataract & Refractive Surgery, Dimitri T. Azar, M.D., field chair of ophthalmologic research and head, Department of Ophthalmology and Visual Sciences, and professor, University of Illinois Eye and Ear Infirmary, Chicago, found that LASIK in patients with –6 to –10 D of myopia was safe, although efficacy and predictability were slightly lower.
Dr. Azar said that he continues to analyze and report LASIK results in unique patient groups, including another recently published study regarding LASIK in patients between the ages of 40 and 69. These kinds of studies help offer patients solid pre-op predictions about surgical outcomes, Dr. Azar said.
Technology, a speedy visual recovery
Naturally, surgeons want to know that new technology and techniques—be it wavefront-guided LASIK or an approach such as sub-Bowman’s keratomileusis (SBK)—are safe and equally, if not more, effective compared with their original procedure. This is an area that will always merit further research, Dr. Schallhorn said.
For example, studies of ultra-thin flaps such as those made during SBK may attract special attention in the future. “For most folks with the femtosecond laser, the average flap is 100 microns, but can we do 80 microns? Right now, we really can’t. As the technology improves, can we make an 80-micron flap, and does it result in better outcomes? We’ll need to look at the implications of that,” he said.
Improved contrast sensitivity and the unintentional creation of higher-order aberrations are two other technology-related areas that surgeons would like to see explored.
Some ophthalmologists also would like the procedure to have an even faster visual recovery—so fast, perhaps, that one might liken it to a dentist appointment, Dr. Durrie said. “We need to look at getting vision to 20/20 in an hour. It’s possible with the phakic IOLs,” he said.
Studies related to visual recovery could help determine whether military patients such as aviators can return to their work after one or two weeks instead of the current one-month wait, Dr. Schallhorn said.
Ultimately, the results from safety and efficacy studies should boost patient satisfaction with the procedure and give surgeons better information to present to patients during pre-op discussions, Dr. Lindstrom said.

Editors’ note: Dr. Durrie has financial interests with Advanced Medical Optics (AMO, Santa Ana, Calif.) and Alcon (Fort Worth, Texas), among other ophthalmic companies. Dr. Lindstrom has financial interests with AMO, Alcon, and Bausch & Lomb (Rochester, N.Y.), among other ophthalmic companies. Dr. Schallhorn has financial interests with AMO. Drs. Azar and Tanzer have no financial interest related to their comments.

Contact Information

Azar: 312-996-6590, dazar@uic.edu
Durrie: 913-491-3330, ddurrie@durrievision.com
Lindstrom: 612-813-3633, rllindstrom@mneye.com
Schallhorn: 619-920-9031, scschallhorn@yahoo.com
Tanzer: David.Tanzer@med.navy.mil