Fiat Lux: the effect of illuminance on acuity testing

Purpose To determine the effect of changing illuminance on visual and stereo acuity. Methods Twenty-eight subjects aged 21 to 60 years were assessed. Monocular visual acuity (ETDRS) of emmetropic subjects was assessed under 15 different illuminance levels (50–8000 lux), provided by a computer controlled halogen lighting rig. Three levels of myopia (−0.50DS, −1.00DS & 1.50DS) were induced in each subject using lenses and visual acuity (VA) was retested under the same illuminance conditions. Stereoacuity (TNO) was assessed under the same levels of illuminance. Results A one log unit change in illuminance level (lx) results in a significant change of 0.060 LogMAR (p