Study: Some RP abnormalities are linked with lower visual acuity

This article was reviewed by J. Fernando Arevalo, MD

The new generation of genetic mapping provides more information about retinitis pigmentosa (RP), which should help identify new treatment approaches.

A recent study showed that patients with an identified pathogenic variant had lower visual acuity (VA) levels that were associated with the length of the inner segment/outer segment (IS/OS) junction.

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Investigators conducted a retrospective, observational case study to determine the ocular characteristics and genes affected in patients with a clinical diagnosis of RP.

Twenty-one patients who had been diagnosed with RP underwent a comprehensive ophthalmologic examination that included spectral-domain optical coherence tomography to measure the central retinal thickness (CRT) and the length of the foveal IS/OS junction.

Blood samples were analyzed for sequencing and deletion/duplication testing for 248 genes, according to Agustin Loria, MD, a retina fellow at Valley Retina Institute in McAllen, Texas.

Findings
Overall, the mean visual acuity was 1.21 logarithm of the minimum angle of resolution (logMAR), mean IOP 14.9 mm Hg, mean CRT 232 μ, and mean IS/OS junction length 1526 μ.

The investigators identified a pathogenic variant in 14 of the 21 patients. The most common of these were variants in the following genes: the USH2A gene in 50% of patients, followed by ABCA4 and BBS5 in 14.2% each, and CDH3, CRKL, BBS10, and PDE6B in 7.14% each, Loria noted.

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The patients were divided into groups A and B based on the classification of the genetic variant, that is, group A, those with a pathogenic variant, and group B with an uncertain significance variant, he explained.

In group A, the mean VA was 1.47 logMAR, IOP 13 mm Hg, CRT 226.1 μ, and IS/OS junction length 683.86 μ. In group B, the respective values were 1.18 logMAR, 15 mm Hg, 236.46 μ, and 1577.63 μ.

“Even though not all the patients had pathogenic variants, all of them demonstrated typical phenotypic and clinical findings associated with retinitis pigmentosa,” Loria concluded. “We found that patients with pathogenic variants had lower VA that was correlated with the length of the IS/OS junction.”

Future studies with more patients are needed to confirm these results, Loria noted.

Read more by Lynda Charters

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Agustin Loria, MD
e: aloria@vritx.com
Loria has no financial interest in this subject matter.