Scotopic microperimetry: evolution, applications and future directions

Abstract

For many inherited and acquired retinal diseases, reduced night vision is a primary symptom. Despite this, the clinical testing options for spatially-resolved scotopic vision have until recently been limited. Scotopic microperimetry is a relatively new visual function test that combines two-colour perimetry with fundus-controlled perimetry performed in scotopic luminance conditions. The technique enables spatially-resolved mapping of central retinal sensitivity alongside the ability to distinguish between rod and cone photoreceptor sensitivities. Two companies produce commercially available scotopic microperimeters -Nidek (Nidek Technologies Srl, Padova, Italy) and CenterVue (CenterVue S.p.A., Padova, Italy).Scotopic microperimetry is a promising technology capable of detecting changes in retinal sensitivity before changes in other measures of visual function. Scotopic microperimetry is a promising functional biomarker that has potential as a useful clinical trial outcome measure. In this review, we summarise the evolution and applications of scotopic microperimetry, discuss testing options, including testing grid selection and dark-adaptation time and threshold sensitivity analyses.

A cross-sectional study to assess the clinical utility of modern visual function assessments in patients with inherited retinal disease: a mixed methods observational study protocol

“…Scotopic microperimetry is a modified version of microperimetry, that is performed at much lower light levels, using two-colour perimetry to target a spatial assessment of rod and cone photoreceptor scotopic function [ 24 ]. For clinical trials, this test could be incredibly useful in identifying rod or cone specific photoreceptors responding to treatments.…”

Choroideremia: The Endpoint Endgame

“…The technique enables the spatially resolved mapping of central retinal sensitivity alongside the ability to distinguish between rod and cone photoreceptor sensitivities, using cyan (505 nm) and red (627 nm) stimuli. Scotopic microperimetry has the potential to detect retinal sensitivity changes in patients with early-stage choroideremia; however, its utility as an outcome measure in choroideremia has yet to be explored [ 56 ].…”

Assessment of Scotopic Function in Rod–Cone Inherited Retinal Degeneration With the Scotopic Macular Integrity Assessment

“… 15 , 16 However, in patients with both stable and unstable fixation, gaze-contingent testing (so-called microperimetry or fundus-controlled perimetry) is preferable to ensure accurate stimulus placement during and across examinations. 17 , 18 Detailed measurement of the visual fields can be performed with devices such as the macular integrity assessment (MAIA) (Centervue, Padova, Italy) but standard protocols are performed under mesopic conditions. Recently, the MAIA device has been updated and is now capable of performing scotopic testing of both rods and cone, (known as the scotopic MAIA [S-MAIA]).…”

“…Recently, the MAIA device has been updated and is now capable of performing scotopic testing of both rods and cone, (known as the scotopic MAIA [S-MAIA]). 18 For a clinical trial setting, using an existing device approved by the US Food and Drug Administration provides advantages regarding the acceptability of the results produced. The S-MAIA uses cyan stimuli (505 nm) and red stimuli (627 nm) with the difference calculated between them.…”

“…The original version had a decreased decibel range of testing under scotopic testing, but this range has since been expanded to the full 36 dB in all conditions to remove any ceiling effects and allow lower intensity lights to be presented. 18 However, the decibel scale used for scotopic tests is not directly comparable with the mesopic tests because it uses the scotopic candela per square meter scale. Both the cyan and red stimuli are thought to be rod mediated in healthy observers outside of the central retina, which features the rod-free zone.…”