Dissociation of rod and cone sensitivity by acute localized retinal pigment epithelium loss

Abstract

To assess the impact of acute retinal pigment epithelium (RPE) loss on photopic and scotopic sensitivity. A 68-year-old woman who had been followed for drusenoid RPE detachment in age-related macular degeneration presented with an acute spontaneous retinal pigment epithelium tear. Three months later, she was seen for routine follow-up and was examined by manual photopic and scotopic threshold perimetry (a static 0.46-degree-diameter 660 nm stimulus under photopic conditions; then, following 25 min of dark adaptation, a static 0.46-degree-diameter 532 nm stimulus under scotopic conditions). The stimuli were applied over the RPE defect and at reference points of similar eccentricity in the opposite vertical haemifield of the same eye where the RPE remained present. Acute RPE loss was associated with only a marginal reduction of photopic sensitivity (-1.5 dB) but a pronounced loss of scotopic sensitivity (-19.5 dB). Our observations show that RPE is essential for scotopic but not for photopic retinal function, supporting the theory that cone photopigment regeneration occurs within the human neurosensory retina independently of the RPE.