Abstract
Purpose: :
To measure distance, intermediate and near visual acuity in simulated presbyopia when refraction is optimally corrected with spectacles for distance. The advantage of binocular over monocular is also assessed.
Methods: :
Participants were 34 healthy, young (average age: 27±5 years) emmetropes or myopes (average spherical equivalent: -2.29±2.05D), with no ocular abnormalities. Presbyopia was simulated with application of cyclopentolate. Visual acuity was assessed monocularly (dominant eye) and binocularly, with an artificial pupil of 3.5mm diameter, using the UoC logMAR charts (Plainis et al., 2007). Measurements were performed with optimal refractive correction for distance at: i) 4m / corrected distance visual acuity (CDVA), ii) 66cm / distance-corrected intermediate visual acuity (DCIVA) and iii) 33cm / distance-corrected near visual acuity (DCNVA). The order of VA testing was counter-balanced.
Results: :
Average (±SD) values were: CDVA -0.11±0.07 and -0.13±0.08 logMAR, DCIVA 0.06±0.09 and 0.01±0.07 logMAR and DCNVA 0.37±0.09 and 0.30±0.10 logMAR with binocular and monocular viewing, respectively. Visual acuity was better with binocular than monocular observation at all distances with the binocular advantage increasing the higher the blur / the nearer the distance (from 0.02 logMAR at 4m, to 0.05 logMAR at 66cm and 0.07 logMAR at the 33cm distance). An analysis of variance (ANOVA) on these data revealed a significant effect of viewing condition (p<0.001) and viewing / distance interaction (p=0.002).
Conclusions: :
The study provides normative distance, intermediate and near visual acuity data in simulated presbyopia when refraction is optimally corrected for distance. Binocular vision improves visual acuity, especially for intermediate and near distances. It should be noted that age-related factors, e.g. neuronal degeneration, increased ocular scatter, may lead to reduced visual acuity values in real presbyopic eyes.
Keywords: visual acuity • binocular vision/stereopsis • pattern vision