Abstract
Background: Tests of visual function assess the eye and visual system. Factors such as ageing, refractive error, strabismus, amblyopia and ocular diseases have a negative effect on different visual functions. Aim: To determine the effect of induced blur on three measures of distance visual function (visual acuity, stereopsis and contrast). Setting: University of KwaZulu-Natal eye clinic. Methods: A quasi-experimental research design was adopted and included 30 healthy young adults. Three convex test lenses (1 dioptre [D], 3 D and 5 D) were used to induce blur and a lens of no power (0 D) was a placebo. The binocular visual acuity (BVA), stereoacuity and binocular contrast were assessed with the LogMAR chart, Howard–Dolman apparatus and Lea low contrast test, respectively. Tests of visual function were measured with no test lens (habitual measurement), and also with each test lens. Data were analysed using descriptive and inferential statistics. Results: The mean habitual BVA and stereoacuity were 0.01 LogMAR ± 0.05 LogMAR and 29 arcsec ± 20 arcsec, respectively. The mean BVA and stereoacuity measurements with the convex test lenses were ≥ 0.24 LogMAR and ≥ 62 arcsec, respectively and significantly different from the habitual measurements ( p < 0.001). Most participants were unable to achieve the habitual contrast level with the three convex test lenses. Conclusion: Induced blur reduced the three measures of distance visual function and the decrease was proportional to the power of the convex test lens. These findings should be considered when screening uncorrected ametropes for eligibility for a driver’s licence.
Highlights
The term visual function describes how well the eye and visual system work and may be assessed with various tests in a clinical and/or research setting.[1]
Even though the 1 D test lens influenced acuity, stereopsis and contrast, the study findings suggest that the 3 D and 5 D test lenses resulted in a substantial decrease in all three measures of distance visual function
The present study assessed the effect of induced blur on three measures of distance visual function including BVA, stereoacuity and contrast
Summary
The term visual function describes how well the eye and visual system work and may be assessed with various tests in a clinical and/or research setting.[1]. Distance vision tasks refer to activities that are performed usually beyond 4 metres (m).[4] Unlike near-vision tasks that are most often sedentary activities, distance vision tasks are related to mobility and include dynamic activities such as driving and engaging in sports as well as leisure activities.[5] In a qualitative study that used methods such as focus groups, interviews, reflective journals and a questionnaire, to investigate the types of visual tasks performed at different distances, Atkinson et al.[4] reported that driving was the most frequently mentioned distance vision activity This is not surprising as driving is a favoured means of travel for many individuals worldwide.[6] A systematic review reported that driving cessation is associated with poor quality of life, feelings of social isolation, reduced access to healthcare services as well as decreased physical and mental health.[7] When interacting with the visual environment to undertake a http://www.avehjournal.org. Refractive error, strabismus, amblyopia and ocular diseases have a negative effect on different visual functions
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