Resolution acuity across the visual field for mesopic and scotopic illumination

Area of Science:

• Vision science
• Neuroscience
• Ophthalmology

Background:

• Visual acuity typically decreases with lower light levels.
• The relationship between retinal illuminance and visual acuity is complex and not fully understood.
• Previous studies often confounded illuminance with retinal location.

Purpose of the Study:

• To investigate the relationship between retinal illuminance and visual acuity at fixed retinal eccentricities.
• To elucidate the mechanisms underlying decreased visual acuity at low light levels.
• To provide a mechanistic interpretation for clinical low-luminance visual dysfunction metrics.

Main Methods:

• Experiments were conducted while holding retinal eccentricity constant and varying retinal illuminance.
• Visual acuity was measured across different retinal locations and illuminance levels.
• Results were compared with the anatomical sampling density of retinal neurons.

Main Results:

• Visual acuity at a fixed retinal location is largely independent of illuminance.
• Under free-viewing, acuity improves with illuminance due to migration to the high-acuity fovea.
• Scotopic acuity in central retina is limited by A-II amacrine cell spatial summation.

Conclusions:

• Retinal location is a critical factor in visual acuity, especially under varying light conditions.
• Midget ganglion cell spacing limits mesopic and peripheral scotopic acuity.
• A-II amacrine cells contribute to central scotopic acuity limitations, offering insights into retinal disease progression.