Scotopic and Photopic Microperimetry in Patients with Reticular Drusen and Age-related Macular Degeneration

Abstract

Purpose: To evaluate retinal function by scotopic and photopic microperimetry patients with age-related macular degeneration (AMD) and a well-demarcated area of RDR (reticular drusen).

Methods: A prospective case series of 22 eyes from 18 patients (mean age 74.7 years, range 62-87) was performed. Using combined confocal scanning laser ophthalmoscopy and spectral-domain optical coherence tomography imaging, retinal areas with RDR (category 1), other AMD-related pathologies (category 2) and no visible pathological alterations (category 3) were identified in each eye. Scotopic and photopic microperimetry (MP1S, Nidek Technologies, Padova, Italy) was performed using a grid with 56 stimulus points. A comparison of the mean threshold sensitivities for each category for scotopic and photopic microperimetry was performed.

Results: In all eyes, areas of categories 1 and 2 showed a relative and sharply demarcated reduction of scotopic threshold values compared to areas of category 3, while only less pronounced differences were seen for photopic testing. Statistical analysis in the 18 eyes in which the 1.0 log unit neutral density filter was applied revealed a significant difference of scotopic threshold values in areas of category 1 (mean 13.5 ± 3.2 dB), category 2 (mean 7.8 ± 4.4 dB) and category 3 (mean 18.3 ± 2.0 dB) (p = 0.002). For photopic testing, the mean threshold values were 16.8 ± 2.9 dB in category 1, 15.9 ± 5.4 dB in category 2 and 18.4 ± 2.7 in category 3 (p = 0.03). Subtracting the scotopic from the corresponding photopic threshold value for each test point, the mean difference was 3.6 ± 3.0 dB for category 1, 8.1 ± 4.0 dB for category 2 and 0.1 ± 2.3 dB for category 3 (p = 0.002).

Conclusions: The results indicate that rod function is more severely affected than cone function in areas with RDR and other AMD-related pathological alterations. This differential structure-function correlation underscores the functional relevance of RDR in AMD subjects.