Association Between Retinitis Pigmentosa and Macular Edema

A study published in Scientific Reports confirmed previously identified retinal structural associations between macular edema (ME) and retinitis pigmentosa (RP), in addition to identifying possible new genetic associations with ME.

The researchers also suggest possible new genetic associations with macular edema, which warrant further investigation.

Macular edema ( ME) is most often the consequence of hyperpermeable retinal blood vessels causing extraversion of fluid into the retinal interstitium, although several pathological ophthalmic diseases have been associated with ME. Retinitis pigmentosa (RP) is made up of a group of inherited diseases that have a similar phenotype, with more than 60 genes known to cause retinitis pigmentosa (RP).

The prevalence of MS in RP has ranged from 8% to 58% in previous literature, and this study aimed to obtain information on whether there are clinical features or genetic associations of MS in RP in a large cohort of RP cases. in which most patients had testing for genetic diseases.

The UC San Diego Inherited Retinal Diseases (IRD) database was used to identify patients. Patients who were seen by retinal physicians between June 2008 and July 2021 were included in the database, and diagnoses of RP were confirmed by a history of progressive loss of peripheral vision or nyctalopia and by findings of RP on examination. ocular. All eyes were imaged and all included patients underwent genetic testing using blood or saliva samples.

There were 571 patients in the database with suspected IRD, and 287 eyes of 145 patients had PR and imaging available. The cohort had a mean (SD) age of 49.73 (19.75) years. MS was found to be more prevalent in the younger age group compared to the older age group (68.9% vs 60.3%).

A validation study was performed to find agreement between 2 independent retina specialists in the classification of EM, epiretinal membrane (ERM), posterior vitreous detachment (PVD), and vitreo-macular traction (VMT). There was an agreement of 92.5% with a Cohen’s Kappa of 0.850. Both raters combined had an agreement of 88.80% and a Cohen’s Kappa score of 0.77.

There were 186 eyes, or 73.1% of all eyes included in 106 patients, that had MS, with MER, PVD, and VMT frequently identified. Intraretinal fluid and foveal thickness were found to be significantly associated with EM in a c2 test; better visual acuity was associated with less MS. Autosomal dominant variants (mean, 6.3%) also had a higher prevalence of macular edema (ME).

The presence of epiretinal membrane (ERM) (mean, 12.4%) and macular edema (ME) was found to have an association when Fisher’s test was used for analysis; VMT also showed a significant association with macular edema (ME) (mean, 4.9%). X-linked inheritance (mean, 6.3%) was found to have an association with the presence of MS when analyzing associations in genetic inheritance. No association was found between previous cataract surgery and MS. When analyzing other genetic associations, only RPI and EYS were found to have a significant association with MS.

There were some limitations to this study. The retrospective nature meant that some patients were excluded due to missing images. The molecular causes of RP are also likely underreported due to the type of genetic testing performed. Genetic associations with RP features are likely underreported because the molecular cause of inherited retinal diseases (IRDs) can only be identified in 60%–70% of cases. Sample sizes were relatively small for each individual gene. 7 families were included, which could be a confounding factor. The types of MS were also not observed and there was a lack of angiography testing in the population.

The researchers concluded that "the present study confirms the retinal structural associations identified in previous studies and adds to the literature on MS associations in RP." Genetic associations with MS have also been suggested and require future research.