Dark adaptometry and dark-adapted two-color microperimetry in patients with Pseudoxanthoma elasticum

Abstract

Purpose : To investigate the impact of pathologically altered Bruch’s membrane on dark adaption and low-luminance conditions in patients with Pseudoxanthoma elasticum (PXE).

Methods : Dark adaptation was measured after bleaching (10 minutes, 1600 apostilb) with a 11° stimulus in 35 PXE patients and 35 age-matched controls (Goldmann-Weekers Adaptometer, Haag-Streit, Switzerland). Low luminance deficit and contrast sensitivity were assessed in the same cohorts. In addition, mesopic and dark-adapted two-color (cyan [505 nm] and red [627 nm]) fundus-controlled microperimetry (10-2 test grid, Goldmann III stimuli; S-MAIA, CenterVue; italy) was performed in 20 eyes of 20 PXE patients and compared to age-adjusted normative data in a point-wise manner. The results were analyzed using linear regression and t-tests.

Results : PXE-eyes (age 49.1 ±11.7 years) exhibited an overall prolonged dark adaptation with high interindividual differences compared to controls (52.2 ±12.2 years). The time to adaptation of 4 log Units was significantly longer in PXE-Patients compared with controls (20.1±8.6 vs. 7.7 ±1.3 minutes, p<0.001). Higher low luminance deficit (mean 6.9 ± SD 4.5 ETDRS letters vs. 14.2 ± 7.5 EDTRS letters) and lower contrast sensitivity ((1.31 ±0.36 vs. 1.96 ±0.16 [logUnits]) compared with controls were measured (p<0.001 respectively). On microperimetry, PXE patients exhibited significant dysfunction compared to age-adjusted normative data with average sensitivity losses of -4.79±3.54 dB for mesopic, -3.81± 5.95 dB for dark-adapted cyan and -5.33 ± 4.32 dB for dark-adapted red testing (p<0.001 respectively). Point-wise analysis revealed that that mesopic sensitivity loss was mostly observable for test-points exhibiting dark-adapted cyan sensitivity losses of -14 dB or greater.

Conclusions : The findings indicate that patients with PXE exhibit prolonged dark adaptation kinetics and generally reduced visual function in low ambient light conditions. Impaired permeability of Bruch’s membrane for retinoid cycle intermediates may contribute to these impairmants, while the exact cause currently remains to be determined. Since Bruch’s membrane aging is a pathogenetic factor in age-related macular degeneration (AMD), these findings could add to the understanding of the pathophysiology in AMD.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.