Major Articles
Stereoacuity and foveal fusion in adults with long-standing surgical monovision*,**,*

Presented at the 27th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Orlando, Florida, March 21-25, 2001.
https://doi.org/10.1067/mpa.2001.119785Get rights and content

Abstract

Purpose: Although binocular vision deficits occur in children who have a constant esotropia onset following significant maturation of stereopsis, it is uncertain whether adults are susceptible to changes to binocular vision. We examined binocular vision in adults with longstanding surgical monovision (≥6 month's duration) to determine whether the binocular visual system remains susceptible to change. Methods: Participants included 32 adults with longstanding monovision through laser-assisted in situ keratectomy or photorefractive keratectomy and 20 age-matched control subjects. After full binocular correction, binocular function was measured by using the Randot Stereoacuity Test, the Randot Preschool Stereoacuity Test, and the Worth 4-dot test at near and distance. Monovision patients were grouped as having low anisometropia (<1.5 spherical D) or moderate anisometropia (≥1.5 spherical D). Results: Non-parametric analysis of variance revealed a significant difference between group median stereoacuity (H = 16.062; P <.001). Pairwise multiple comparisons indicated both groups with monovision had significantly worse stereoacuity compared with control subjects (P <.05). Median stereoacuity values were 100 seconds of arc for patients with low anisometropia, 150 seconds of arc for patients with moderate anisometropia, and 40 seconds of arc for control subjects. A larger proportion of patients with moderate anisometropia failed the Worth-4 dot test at distance than control subjects (z = 2.619; P =.009). Conclusions: Reduced stereoacuity and an absence of foveal fusion in adults with longstanding surgical monovision suggest continued susceptibility of the binocular visual system to anomalous binocular experience. (J AAPOS 2001;5:342-7)

Section snippets

Subjects

Subjects included 32 consecutive adults with monovision produced by LASIK or PRK surgery and 20 age-matched control subjects. Patients enrolled were those who chose to have LASIK or PRK surgery to produce distance vision in their dominant eye and near vision in their nondominant eye, eliminating the need for optical correction for both distance and near viewing. At the time of testing, all participants had monovision for at least 6 months duration (mean duration, 14.5 months; range of duration,

Results

Longstanding surgical monovision had a significant effect on random dot stereoacuity (Kruskal-Wallis one-way ANOVA by ranks: H = 16.062; P <.001). As shown in Figure 1, pairwise multiple comparisons indicated both groups of surgical monovision patients had significantly worse random dot stereoacuity compared with age-matched control subjects (Dunn's pairwise comparisons, P <.05).

. Random dot stereoacuity (seconds of arc) of age-matched control subjects and patients with longstanding surgical

Discussion

The disruption of binocularity by anisometropia that leads to amblyopia and a loss of binocularity in the young of the species, including cats,17, 18 primates,19 and humans,3, 5, 20 is a well-documented adverse outcome. Monovision is an anisometropia that is artificially created for the adult presbyope for the purpose of achieving 20/20 vision at near and at far viewing distances without bifocal correction. Several studies of binocular function in presbyopes with monovision corrections report

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    *

    Supported by Fight for Sight PD99007 and National Institutes of Health EY05236.

    **

    This study was conducted at the private practices of Drs Alfieri and Castleberry.

    *

    Reprint requests: Sherry Fawcett, PhD, Retina Foundation of the Southwest, 9900 N. Central Expressway, Suite 400, Dallas, TX 75231 (e-mail: [email protected]).

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