February 2009

 

REFRACTIVE SURGERY

 

SBK over PRK?


by Matt Young EyeWorld Contributing Editor

   
CK template Seen here, CK template; CK enhances the ophthalmologist’s refractive choices, but it isn’t nearly as popular as LASIK Source: James J. Salz, M.D.

Today, refractive surgeons have a wide range of options to treat potential patients, but what actually is popular and what isn’t? Durrie Vision, Overland Park, Kan., recently evaluated procedure choices in a scientific study. “We performed a retrospective case review of 200 consecutive refractive patients to quantify the refractive surgery trends taking place in our practice,” according to the researchers, who included George O. Waring IV, M.D., and Daniel S. Durrie, M.D., clinical professor of ophthalmology, University of Kansas, Overland Park, Kan. Their study was published in the April 2008 supplement of the Journal of Refractive Surgery. While clearly each surgical center will have its own preferences, this study may help yield insights into why certain methods have become more popular than others. If your own surgery center operates completely differently, it may also be worth asking yourself: why?

Popularity contest results

In their analysis of 200 consecutive refractive patients, researchers went through all the typical motions, checking age, manifest refraction spherical equivalent (MRSE), pachymetry, topographic symmetry patterns, and other measures. Patients were offered one of the following procedures: sub-Bowman’s keratomileusis (SBK), PRK, CK, phakic IOLs, or refractive lens exchange (RLE). Corneal refractive surgery was performed with either the wavefront-optimized Allegretto WaveLight laser (Alcon, Fort Worth, Texas) or wavefront-guided LADARVision 4000 laser (Alcon). SBK flaps were created with the 60-kHz IntraLase femtosecond laser (Advanced Medical Optics, Santa Ana, Calif.). Of the patients analyzed, 69% were advised to undergo SBK; 16% were recommended RLE; 6% PRK; 5% CK; and 4% phakic IOLs. Each patient was treated with the same surgical modality in all cases. It also was interesting to note the ages of patients that were recommended each type of procedure. The mean age overall was 44 years. For corneal excimer procedures, the mean age was 42. It was 57 for RLE, 52 for CK, and 37 for phakic IOL. The mean MRSE, overall, was –2.78 D. It was –2.97 for corneal excimer procedures, –0.54 for RLE, –0.09 for CK, and –9.54 for phakic IOL. Of all patients, 75% were deemed to be candidates for corneal excimer procedures. Clearly, the excimer laser plays a big role in surgery. Among those receiving excimer laser treatment (151 patients), 88% were scheduled for wavefront-optimized treatment and 12% for wavefront-guided. “A wavefront-optimized ablation was recommended in 90% of SBK patients because of minimal preoperative asymmetry and irregular astigmatism,” researchers noted. “Wavefront-guided ablation was recommended for the 10% of patients with higher preoperative aberrations.” Interestingly, more eyes in the PRK group had asymmetric topographic patterns than in the SBK group, which also appears to have led to more widespread use of wavefront-guided surgery for the PRK group. In the SBK group, 55% had symmetric topographic patterns, 33% were borderline, and 12% were asymmetric. In the PRK group, 48% of eyes had asymmetric patterns, 17% were borderline, and 35% were asymmetric. For PRK patients, wavefront-optimized was still recommended in 64%—but a percentage that clearly was lower than in the SBK group. Wavefront-guided was recommended in 36% of PRK patients.

The winning rationale

SBK clearly is the dominant procedure at Durrie Vision, so much so that PRK looks like it has little use. Why? “We have demonstrated in a multicenter prospective, contralateral study that patients who receive SBK benefit from the quick visual recovery of LASIK, and biomechanical outcomes equivalent to PRK, within the limits of current evaluation,” the researchers reported. “As a result, we are performing an increasing number of SBK procedures on borderline cases that we may have previously suggested a surface procedure, prior to the advent of SBK.” If a patient has a single borderline risk factor, the researchers noted they would consider SBK with informed consent. They still liked PRK for anterior basement membrane dystrophy. The researchers suggested that they had seen the mean age for RLE decrease over the years and expected it to decrease more from the 57-year mean in this study. CK was recommended for “plano or near plano … presbyopes,” the researchers reported. Phakic IOLs were recommended for patients with moderate to severe myopia “who are not otherwise structurally or optically candidates for corneal refractive surgery.”

William Trattler, M.D., director, Cornea, Center for Excellence in Eye Care, Miami, said that his practice is also favoring SBK over other procedures. “It’s very safe with good results. We’re nearly 70% SBK,” he said, suggesting a rate very similar to Durrie Vision. One of the differences with his clinic, however, is that it provides wavefront-guided treatments in 80% to 90% of cases.

“Our PRK numbers probably are a little higher, too,” he said. “A couple of our doctors perform a lot of PRK. We’re probably closer to about 12% to 15% PRK.” His clinic’s CK and phakic IOL numbers come in lower than at Durrie Vision, each at about 1% or less of procedures. Dr. Trattler suggested that ophthalmologists originally had higher hopes for both phakic IOLs and CK. In the case of phakic IOLs, expense has been prohibitive as it is not covered by insurance. In CK, there can be regression and finding the right patients who are near plano and at the right age is important, he said.

Editors’ note: Dr. Waring has no financial interests related to this study. Dr. Durrie has financial interests with Alcon (Fort Worth, Texas). Dr. Trattler has no financial interests related to his comments.

Contact information

Durrie: 913-491-3330, ddurrie@durrievision.com
Trattler: 305-598-2020, wtrattler@earthlink.net

SBK over PRK? SBK over PRK?
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