Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences

Abstract

Despite the large amount of variation found in the night (scotopic) vision capabilities of healthy volunteers, little effort has been made to characterize this variation and factors, genetic and non-genetic, that influence it. In the largest population of healthy observers measured for scotopic visual acuity (VA) and contrast sensitivity (CS) to date, we quantified the effect of a range of variables on visual performance. We found that young volunteers with excellent photopic vision exhibit great variation in their scotopic VA and CS, and this variation is reliable from one testing session to the next. We additionally identified that factors such as Circadian preference, iris color, astigmatism, depression, sex and education have no significant impact on scotopic visual function. We confirmed previous work showing that the amount of time spent on the vision test influences performance and that laser eye surgery results in worse scotopic vision. We also showed a significant effect of intelligence and photopic visual performance on scotopic VA and CS, but all of these variables collectively explain <30% of the variation in scotopic vision. The wide variation seen in young healthy volunteers with excellent photopic vision, the high test-retest agreement, and the vast majority of the variation in scotopic vision remaining unexplained by obvious non-genetic factors suggests a strong genetic component. Our preliminary genome-wide association study (GWAS) of 106 participants ruled out any common genetic variants of very large effect and paves the way for future, larger genetic studies of scotopic vision.

The “speed” of acuity in scotopic vs. photopic vision

“…There are some differences between the present study and Bartholomew et al's study [19]. These could have an effect on the study outcome.…”

“…A few also assessed conditions with lower luminance, albeit only covering a very limited parameter range [ 1 ] or restricted to mesopic conditions [ 17 , 18 ]. Bartholomew et al [ 19 ] found preliminary evidence for a duration effect under scotopic conditions. In their study, participants who took longer to respond to an optotype typically produced better acuity values under scotopic conditions.…”

Macular Inner Retinal Layer Thickness in Relation to Photopic and Mesopic Contrast Sensitivity in Healthy Young and Older Subjects

“…The level of 10 cd/m 2 was chosen because this is the most common perimetry background photopic light level; 1 cd/m 2 was chosen to minimize the higher variability in CS produced when low light levels are used. 31 Mean screen luminance was reduced from 10 cd/m 2 to 1 cd/m 2 using one neutral density filter (type 211, 0.9 log units [LEE Filters Worldwide, Andover, Hampshire, UK]). Although a 10 cd/m 2 light source viewed through a 0.9 log units filter gives a theoretical luminance of 1.26 cd/m 2 , the filter is not totally flat and the luminance measured with a light meter (MAVO-SPOT 2 USB light meter; Gossen Lighting Control, Nuremberg, Germany) was 1 cd/m 2 .…”

An Assessment of the Contrast Sensitivity in Patients with Ametropic and Anisometropic Amblyopia in Achieving the Corrected Visual Acuity of 1.0

“…VA and CS are two different but important parameters that are used to measure visual function. VA describes visual function under high contrast conditions 3 . CS testing, which characterizes the visual function under different spatial frequencies and different luminance, is another powerful technique to quantify the capability of the visual system 4 .…”