Abstract
Purpose :
To determine the relationship between induced spherical defocus and low contrast visual acuity (LVA) in presbyopic and non-presbyopic subjects, and to find the range of spherical powers which produce the same reduction in LVA.
Methods :
Observational, prospective, analytical and transversal study in which LVA in healthy subjects under different levels of spherical defocus ranging from -2.00D (diopters) to +1.00D. LVA was measured using EDTRS (Early Treatment Diabetic Retinopathy Study) optotypes (PVVAT Software, Precision Vision, La Salle II) with logMAR unit notation. Subjects were classified in 2 groups depending on their age, under or over 45 years. Randomized Complete Block Design (RCBD) statistical test was used to determine differences in LVA among the different induced powers.
Results :
LVA with different induced lens defocus was evaluated in 10 subjects under 45 years and 21 subjects over 45 years. Differences in the reduction of VA were observed between negative (hyperopia simulation) and positive (myopia simulation) power interposed lens ranges. For the younger group, the defocus induced with negative power lenses did not produce loss of LVA due to their accommodation capacity. For the older group, there was a range between 0 and -0.50D in which LVA remains stable but induced spherical negative power over this range decrease LVA. Defocus induced by positive power lenses produces a deterioration of LVA for all lenses tested (from +0.25D to +1.00D) in both age groups. There are combinations of induced defocus that produce the same loss of visual acuity (figure 1 and 2)
Conclusions :
The results of this investigation help to better understand the relationship between lens induced refractive errors and low contrast VA. The statistical block analysis presented shows correlations between different spherical powers that lead to similar reduction of VA.
This is a 2020 ARVO Annual Meeting abstract.