Imaging Biomarkers of Mesopic and Dark-Adapted Macular Functions in Eyes With Treatment-Naïve Mild Diabetic Retinopathy

Abstract

To investigate the relationship between imaging biomarkers and mesopic and dark-adapted (i.e. scotopic) functions in patients with firstly detected treatment-naïve mild diabetic retinopathy (DR) and normal visual acuity. Prospective cross-sectional study. In this study, 60 patients with treatment-naïve mild DR (ETDRS 20-35) and 30 healthy controls underwent microperimetry, structural optical coherence tomography (OCT) and OCT angiography (OCTA). The foveal mesopic (22.4±4.5 dB and 25.8±2.0 dB, p=0.005), parafoveal mesopic (23.2±3.8 and 25.8±1.9, p<0.0001), and parafoveal dark-adapted (21.1±2.8 dB and 23.2±1.9 dB, p=0.003) sensitivities were reduced in DR eyes. For the foveal mesopic sensitivity, the regression analysis showed a significant topographical association with choriocapillaris flow deficits percentage (CC FD%; β: -0.234, p=0.046) and ellipsoid zone (EZ) "normalized" reflectivity (β: 0.282, p=0.048). The parafoveal mesopic sensitivity was significantly topographically associated with inner retinal thickness (β: 0.253, p=0.035), deep capillary plexus (DCP) vessel length density (VLD; β: 0.542, p=0.016), CC FD% (β: -0.312, p=0.032), and EZ "normalized" reflectivity (β: 0.328, p=0.031). Similarly, the parafoveal dark-adapted sensitivity was topographically associated with inner retinal thickness (β: 0.453, p=0.021), DCP VLD (β: 0.370, p=0.030), CC FD% (β: -0.282, p=0.048), and EZ "normalized" reflectivity (β: 0.295, p=0.042). In treatment-naïve mild DR eyes, both rod and cone functions are affected and they are associated with both DCP and CC flow impairment, which suggests that a macular hypoperfusion at these levels might implicate a reduction in photoreceptor function. The "normalized" EZ reflectivity may be a valuable structural biomarker for assessing the photoreceptor function in DR.