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Comparison of binocular vision status between spectacles & spherical equivalent soft contact lens wear in patients
1Department of Optometry, Himalaya Eye Institute, Pokhara University, Pokhara, Nepal.
Purpose:
To investigate the acute, same-day changes in binocular vision parameters when switching from spectacle wear to spherical-equivalent soft contact lens wear in patients with low myopic astigmatism.
Method:
This acute, same-day comparative study included 36 participants aged 15-35 years with low myopic astigmatism. A comprehensive binocular vision assessment - including accommodative amplitude (AA), accommodative facility (AF), stereoacuity, cover test, horizontal phoria, near point of convergence (NPC), negative relative accommodation (NRA), positive relative accommodation (PRA), positive fusional vergence, negative fusional vergence, and lag of accommodation - was performed with both spectacles and spherical-equivalent soft contact lenses. Measurements were obtained following a 30-minute lens stabilization period. Mean differences between conditions were analyzed using paired t-tests that accounted for within-subject correlation.
Results:
When comparing spherical-equivalent soft contact lenses with spectacles, small but statistically significant differences were observed in selected binocular parameters. The NPC was slightly more receded with contact lenses, with a mean difference of -0.36 ± 0.76 cm compared with spectacles (P < 0.01). The lag of accommodation showed a small reduction with contact lens wear (mean difference: -0.11 ± 0.31 D; P = 0.03). PRA was modestly increased with contact lenses, with a mean difference of +0.35 ± 0.16 D (P = 0.03). No statistically significant differences were found between spectacles and contact lenses for AA, AF, stereoacuity, cover test findings, horizontal phoria, NRA, positive fusional vergence, or negative fusional vergence (all P > 0.05).
Conclusion:
These findings suggest that when low myopic astigmatism is corrected using spherical-equivalent soft contact lenses, certain binocular vision parameters may demonstrate acute changes. Careful binocular vision assessment may therefore be beneficial when prescribing simplified spherical correction in astigmatic patients.
