Photoreceptor Function Reduced in Treatment-Naïve Diabetic Retinopathy

Photoreceptor function may be reduced in untreated eyes with diabetic retinopathy (DR) and be associated with deep capillary plexus (DCP) and choriocapillaris (CC) flow impairment, according to research published in the American Journal of Ophthalmology. Normalized ellipsoid zone (EZ) reflectivity may serve as a biomarker for this photoreceptor dysfunction, the report suggests.

The case-control study included patients with type 1 diabetes (n=30; mean age, 60.1 years; 66.7% men) who had treatment-naïve DR and normal visual acuity and age-matched control group participants (n=30; mean age, 57.8 years; 73.3% men). Study participants underwent microperimetry, structural optical coherence tomography (OCT) and OCT-angiography (OCT-A) assessment. The investigators evaluated imaging biomarkers for mesopic and scotopic functions and calculated normalized EZ reflectivity.

Patients with DR demonstrated reduced photoreceptor function in foveal mesopic (22.4 vs 25.8 dB; P =.005), parafoveal mesopic (23.2 vs 25.8; P <.0001), and parafoveal dark-adapted (21.1 vs 23.2 dB; P =.003) conditions compared with control group participants.

The multiple regression analyses revealed that foveal mesopic sensitivity in patients with DR was associated with foveal EZ normalized reflectivity (β, 0.282; P =.048) and foveal CC flow deficits (β, -0.234; P =.046). Parafoveal mesopic sensitivity was associated with parafoveal DCP perfusion density (β, 0.542; P =.016), parafoveal EZ normalized reflectivity (β, 0.328; P =.031), parafoveal inner retinal thickness (β, 0.253; P =.035), and parafoveal CC flow deficits (β, -0.312; P =.032). Parafoveal dark-adapted sensitivity was associated with parafoveal inner retinal thickness (β, 0.453; P =.021), parafoveal DCP vessel length density (β, 0.370; P =.030), parafoveal EZ normalized reflectivity (β, 0.295; P =.042), and parafoveal CC flow deficits (β, -0.282; P =.048).

“[W]e demonstrated that mesopic and dark-adapted dysfunctions are associated with
both DCP and CC flow impairment, which suggests that a macular hypoperfusion at these levels might implicate a reduction in the photoreceptor function, even in the absence of a thinning of the outer retina,” according to the study authors. “Our results may help broaden our knowledge on the natural history of diabetic retinopathy and the development of vessels’ and neural damage in this disorder. Finally, the ‘normalized’ EZ reflectivity, rather than the outer retinal thickness, if replicated in following reports, may prove to be a valuable structural biomarker for assessing the photoreceptor function in DR eyes.”

Study limitations include a small sample size and cross-sectional nature.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on Optometry Advisor