Abstract
INTRODUCTION: Understanding the link between near visual display device (NVDD) use and the parameters of the eye's accommodation and vergence (PEAV) can impact vision therapy and optometric advice. This study examined the relationship between the duration of NVDD use and PEAV among high school students in Cape Coast, Ghana. METHODS: This school-based cross-sectional study employed multistage sampling to administer reliable questionnaires (on the frequency of NVDD usage, ergonomic factors and computer vision syndrome symptoms) to 326 high school students. The PEAV were assessed over maximum plus for the best-corrected visual acuity refractive correction. RESULTS: The duration of usage of NVDD correlated with deteriorations in: measures of latent ocular squints (near heterophoria (r(s)=0.360, p=0.0001)); eye's ability to converge (near point of convergence (r(s)=0.369, p=0.0001)); ability to change between convergence and divergence (vergence facility (r(s)=-0.340, p=0.0001)); ability to compensate for near squints (negative fusional vergence break (r(s)=-0.352, p=0.0001) and positive fusional vergence break (r(s)=-0.322, p=0.0001) at near); refractive power to accommodate (accommodative amplitude (r(s)=-0.340, p=0.0001)); ability to switch between near and distance targets (monocular accommodative facility (r(s)=-0.377, p=0.0001)) and response to focusing a target (accommodative response (r(s)=0.382, p=0.0001)). CONCLUSION: Using NVDD for more than two hours a day correlated with clinically significant deterioration in the PEAV.