Original Research

The effect of induced blur monocularly and binocularly on stereoacuity

Thokozile I. Metsing
African Vision and Eye Health | Vol 82, No 1 | a846 | DOI: https://doi.org/10.4102/aveh.v82i1.846 | © 2023 Thokozile I. Metsing | This work is licensed under CC Attribution 4.0
Submitted: 24 February 2023 | Published: 23 October 2023

About the author(s)

Thokozile I. Metsing, Department of Optometry, Faculty of Health Sciences, University of Johannesburg, Johannesburg, South Africa


Background: Stereopsis plays a significant role in our visual system because it allows perception of depth to perform day-to-day activities.

Aim: The aim of this study was to determine the severity and proportions of monocular versus binocular-induced blur on stereoacuity using the Randot® Stereo Test (RST) at near (40 cm).

Setting: Data were collected at the optometry clinic of the University of Johannesburg.

Methods: The study used a cross-sectional, experimental and prospective design with a quantitative approach. Forty university students between the ages of 18 years and 25 years were invited to participate in this study. Blur was induced monocularly and binocularly through 1 dioptre (D) to 3 D lenses and stereoacuity was measured using the RST at near (40 cm).

Results: Stereoacuity measured with the added 1 D to 3 D lenses monocularly and binocularly resulted in reduced stereopsis, which was worse monocularly, found not to be significant (p = 0.17) with the addition of the 1 D lens(es) monocularly and binocularly. Significant reductions in stereoacuity were found with the addition of 2 D (p = 0.00) and 3 D (p = 0.00) monocularly and binocularly, respectively.

Conclusion: The effect of induced optical blur monocularly on stereoacuity impacted significantly compared with induced binocular blur. However, the different accommodative amplitudes could have affected monocularly and binocularly induced stereoacuity for some participants.

Contribution: The study is clinical and focuses on the effect of induced blur monocularly and binocularly on stereoacuity. Key insights are that the effect of induced optical blur monocularly impacted significantly on stereoacuity compared with induced blur binocularly.


stereoacuity; isometropia; anisometropia; depth perception; induced blur; retinal disparity; optical blur.

Sustainable Development Goal

Goal 3: Good health and well-being


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