April 2019

NEWS

Research Highlight
Myopic view of pigment dispersion syndrome


by Maxine Lipner EyeWorld Senior Contributing Writer


Krukenberg spindle, showing pigment dispersion in a typical pattern on the corneal endothelium
Source: Robert Noecker, MD




Retroillumination defects temporally in the shape of the haptic that is in the sulcus
Source: Jason Jones, MD

 

Among myopes, the prevalence of pigment dispersion syndrome is approximately 26%, according to results of a new study1 by John Doane, MD, and J. Quintin Tuckfield. The condition is particularly common among myopic patients with blue eyes, with a prevalence 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 defects associated with pigment dispersion syndrome. 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, investigators decided that it was time to crunch the numbers. “We were surprised to find that the prevalence 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 study2 showed similar results with iris transillumination defects occurring in 86% of patients. The condition is more likely to occur in those with blue eyes, Dr. Doane noted.
“In our study, we found a much higher incidence 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 study3 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 chambers, 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 myopic 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 characteristics of pigment dispersion syndrome such as Krukenberg spindles or transillumination defects. To spot such signs, the room has to be dark. At the slit lamp, a very small slit has to be used and this has to be pointed directly to the back of the eye to get the reflection off the posterior pole for the transillumination defect to illuminate.
“The take-home message is that it’s very easy to miss the Krukenberg spindles and illumination defects unless you really look for these,” Dr. Doane said. “I think the best recommendation is if you see a myopic patient, you have to be thinking that this is something you want to rule out.”

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 glaucoma 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

Contact information
Doane
: jdoane@discovervision.com

Myopic view of pigment dispersion syndrome Myopic view of pigment dispersion syndrome
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