Non-Strabismic Binocular Vision Dysfunction Among Contact Lens Wearers

Purpose: To investigate the prevalence and types of non-strabismic binocular vision dysfunction (NSBVD) among contact lens wearers. Methods: Participants attended one clinical visit while wearing their habitual contact lenses. Participants were required to have a spherical myopia range between -0.50 D and -12.00 D with ≤ 0.75 D of astigmatism and at least six months of experience wearing single-vision contact lenses. A comprehensive binocular vision assessment was performed, including phoria measurements, amplitude of accommodation, near point of convergence, fusional reserves, and relative accommodation. Results: Sixty-four participants completed the trail, and 15 (23.1%) were diagnosed with NSBVDs. Convergence insufficiency was the most prevalent disorder (7.8%), followed by basic exophoria (3.1%), ill-sustained accommodation (3.1%), and accommodative excess (3.1%). Participants with NSBVDs exhibited significantly higher near exophoria (-6.7 ± 7.2Δ vs. -1.6 ± 2.2Δ, p = 0.03), receded near point of convergence (9.3 ± 3.1 cm vs. 5.5 ± 2.1 cm, p = 0.01), and reduced accommodative facility (monocular: 8.6 ± 5.8 cycles/min vs. 16.4 ± 4.3 cycles/min, p = 0.001; binocular: 4.3 ± 6.7 cycles/min vs. 13.3 ± 3.7 cycles/min, p < 0.001). Reduced fusional reserves and accommodative lag were also observed among affected participants. Conclusion: NSBVD are common among contact lens wearers and may contribute to visual discomfort, impacting contact lens tolerance and overall visual performance. Routine binocular vision assessment in contact lens practice is recommended to optimize visual outcomes and reduce contact lens discontinuation due to undiagnosed binocular vision anomalies.