Eyeworld

N by Maxine Lipner EyeWorld Senior Contributing Writer APRIL 2019 | EYEWORLD | 37 Contact information Doane: jdoane@discovervision.com Myopic view of pigment dispersion syndrome continued on page 39 RESEARCH HIGHLIGHT A mong myopes, the prevalence of pig- ment dispersion syndrome is approxi- mately 26%, according to results of a new study 1 by John Doane, MD, and J. Quintin Tuckfield. The condition is particularly common among myopic patients with blue eyes, with a preva- lence of 35.8%, Dr. Doane said. Studying myopic LASIK practice Dr. Doane, who only performs myopic LASIK, began noticing that many of these patients had Krukenberg spindles and transillumination de- fects associated with pigment dispersion syn- drome. Soon every time a patient came to him for laser vision correction, as part of the preoperative exam, he started looking for transillumination defects and Krukenberg spindles. After collecting data on 637 eyes, investiga- tors decided that it was time to crunch the num- bers. "We were surprised to find that the preva- lence that we had far outranked what you see in the normal literature," Dr. Doane said, adding that most of this involves the general population instead of just the myopic one. He found that of 165 eyes diagnosed with pigment dispersion syndrome 92.7% had iris transillumination defects, 28% had Krukenberg spindles, and 23% had both. Dr. Doane pointed out that a 2003 study 2 showed similar results with iris transillumination defects occurring in 86% of patients. The con- dition is more likely to occur in those with blue eyes, Dr. Doane noted. "In our study, we found a much higher inci- dence of transillumination defects in blue eyes," he said. "The reason it's more common in blue eyes is because brown-eyed patients have two layers of pigment, heavily anterior and posterior, and thicker irises, whereas a blue-eyed patient has no anterior pigment." As a result, all you have to do is rub off the posterior pigment and you begin seeing transillumination defects, he explained. When it came to prevalence, Dr. Doane found this tended to be greater in his study of myopes than in other more general ones. He cited a study 3 based on glaucoma screenings that showed a pigmentary dispersion syndrome prevalence of just 2.5%. In the Siddiqui study, the annual incidence of pigment dispersion syndrome was 4.8% compared with 25.9% in his own study, Dr. Doane said. While both of these populations shared light irises in common, his own study was distinguished by the fact that all of the patients were myopic. Unusual iris configuration This condition is so common in those who are nearsighted because they tend to have deep cham- bers, with a longer axial length. "Myopes tend to have an unusual iris configuration, where the iris flops back posteriorly and rubs on the zonules," Dr. Doane said, adding that you don't see this in hyperopes or those with a normal axial length. When you start to look at this purely in the my- opic population, you get astounding prevalence numbers, he noted. Keeping this in mind, Dr. Doane advises practitioners that when they see nearsighted patients in the clinic, they should look for charac- teristics of pigment dispersion syndrome such as Krukenberg spindles or transillumination defects. About the doctor John Doane, MD Discover Vision Centers Kansas City, Missouri References 1. Doane JF, et al. Prevalence of pigment dispersion syndrome in patients seeking refractive surgery. J Glaucoma. 2019. Epub ahead of print. 2. Siddiqui Y, et al. What is the risk of developing pigmentary glau- coma from pigment dispersion syndrome? Am J Ophthalmol. 2003;135:794–9. 3. Ritch R, et al. Prevalence of pigment dispersion syndrome in a population undergoing glaucoma screening. Am J Ophthalmol. Financial interests Doane: None Krukenberg spindle, showing pigment dispersion in a typical pattern on the corneal endothelium Source: Robert Noecker, MD

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