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Early results show favorable outcome for PRK in keratoconus suspects

PRK may be the best refractive surgical option for patients who are likely to develop keratoconus, surgeon says.

ByDaniele Cruz

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SEATTLE – Early results of PRK in eyes with high coma and trefoil are promising, according to Richard L. Lindstrom, MD.

“We know some day some of these patients may show some progression with time whether we treat them or not,” OSN Global Chief Medical Editor Dr. Lindstrom said in a presentation here. “These are high-risk patients, but we’re basically getting extremely reasonable outcomes.”

He presented the case of a 44-year-old male patient who had mild blurry vision and contact lens intolerance. His refraction was –6.25 +1.50 × 160 yielding 20/25 in the right eye and –6.25 +1.75 × 160 yielding 20/25 in his left eye. Pachymetry was 452 µm in his right eye and 448 µm in his left eye.

“This patient had surface ablation and had a good outcome, achieving 20/25 uncorrected acuity in both eyes, which has remained stable for 3 years,” Dr. Lindstrom said. “This area is difficult. Through the years we’ve done some patients with LASIK in the past, and some have done really well, but others have progressed and we have abandoned LASIK in these cases.”

The long-term outcomes are difficult to project due to potential changes in corneal curvature, Dr. Lindstrom said, and these eyes could possibly require future additional correction with excimer laser, Intacs, CK or even keratoplasty. But many of these patients are contact lens-intolerant and do poorly with glasses, so they are willing to accept an increased risk.

Favorable early outcome

Dr. Lindstrom said it is difficult to predict which patients may progress to keratoconus.

“We have some patients who didn’t have keratoconus 20 years ago, never had surgery, but have it now,” he said. “It is extremely difficult for all of us.”

During his presentation, Dr. Lindstrom also showed an analysis of a series he and colleagues are conducting.

Surgeons at Minnesota Eye Consultants performed PRK on 56 eyes with high coma or trefoil. The eyes had a mean preop spherical equivalent of –3.16 ± 1.74 D. At follow-up visits that ranged from 1 to 7 months, 55 of the eyes had a mean spherical equivalent of –0.05 ± 0.43 D.

“What I have presented here is preliminary, and we are doing further analysis to determine who the best candidates may be — for example, high coma and asymmetric bowtie, mild irregular astigmatism,” he said. “Some of them are very highly motivated to have refractive surgery. It’s always a difficult decision.”

The PRK outcomes are good so far, he said.

The results are not as good as LASIK results in normal eyes, but the results could improve with the use of iris registration technology, he said.

Panel opinion

This session at last year’s ASCRS Refractive meeting featured a panel format, and Dr. Lindstrom asked the panel members for their opinions on treating keratoconus suspects.

R. Doyle Stulting, MD, PhD, said thickness is more of a concern than topography when deciding on a treatment in such a patient.

Topography can be a significant discriminating factor when determining which patients may develop ectasia, but many patients with abnormal topographies have no problems with ectasia at all, he said.

“I think this is a patient who would be reasonable to treat with surface ablation,” Dr. Stulting said in reference to the case. “I wouldn’t do LASIK on him because of the corneal thickness alone, even if topography was normal.”

Roger F. Steinert, MD, agreed that corneal thickness is a concern, but his recommendation was more conservative.

“I would be concerned about PRK and certainly wouldn’t do LASIK,” he said. “I just can’t see the logic of taking away any tissue from this person’s cornea. It may look good for a number of years, and I know people who are doing this, but I think they’re just asking for trouble.”

For Your Information:

• Richard L. Lindstrom, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 106, Minneapolis, MN 55404-3810 U.S.A.; +1-612-813-3633; e-mail: rllindstrom@mneye.com.
• R. Doyle Stulting, MD, PhD, can be reached at the Department of Ophthalmology, Emory University, Atlanta, GA 30319 U.S.A.; +1-404-778-6166; e-mail: ophtrds@emory.edu.
• Roger F. Steinert, MD, can be reached at Eye Institute at University of California, Irvine 118 Med Surge I Zot 4375, Irvine, CA 92697-4375 U.S.A.; +1-949-824-8089; e-mail: steinert@uci.edu

• Daniele Cruz is an OSN Staff Writer who covers all aspects of ophthalmology.