EFFECT OF SUSTAINED NEAR WORK ON ACCOMMODATION AND VERGENCE IN SUBJECTS WITH LOW HYPEROPIA
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Abstract
Sustained near work has become a common visual demand in this digital era, often placing considerable strain on the accommodative and vergence systems, particularly in individuals with uncorrected refractive errors such as low hyperopia. This study aimed to evaluate the effect of sustained near work on accommodative and vergence parameters in individuals with low uncorrected hyperopia and to assess the influence of optical correction on these visual functions. Fifty-five participants consisting of 12 males and 43 females aged between 16–30 years (with mean age 20 ± 2.0 years) with low uncorrected hyperopia were assessed. Baseline measurements of amplitude of accommodation (AA), positive and negative relative accommodation (PRA, NRA), near point of convergence (NPC), and fusional vergence ranges (PFV and NFV) were obtained. Thereafter the subjects were made to read a printed text with Times New Roman font size 12 for 30 minutes first without correction and thereafter for another 30 minutes with correction. Post-task measurements for each were taken. Result obtained showed a systemic increase in mean AA (9.70 ±2.40 D to 10.30 ± 2.60 D) and PRA (-4.90 ± 1.48 D to -5.45 ± 1.36 D) and a decrease in PFV (BO to Break 20.00 ± 5.00Δ to 17.00 ± 6.00Δ) while there was minimal to no change in NRA (+2.82 ± 0.76 D to +2.50 ± 0.59 D) and NFV (BI to Break 14.00 ± 4.00 Δ) before and after sustained near task without correction. Also, there was an increase in mean AA (9.70 ±2.40 D to 11.30 ± 3.40 D) and PRA (-4.90 ± 1.48 D to -5.78 ± 1.66 D) and a decrease in PFV (BO to Break 20.00 ± 5.00Δ to 17.00 ± 7.00Δ) while there was minimal to no change in NRA (+2.82 ± 0.76 D to +2.30 ± 0.47 D) and NFV (BI to Break 15.00 ± 4.00 Δ) pretask and post-task with correction. The result was analyzed using Friedman’s ANOVA and repeated measures ANOVA to compare pre- and post-task differences. This showed a significant difference between AA, PRA and PFV without and with correction (Z = −3.289, p = 0.003; F = 19.63, p < 0.001 and Z = 3.194, p < 0.001 respectively). However, there was no significant difference between pre and post task NRA, NPC and NFV without and with correction (p > 0.001). The findings suggest that sustained near work imposes temporary stress on the accommodative and vergence systems in individuals with low uncorrected hyperopia, and that optical correction effectively reduces this strain, improving visual comfort and performance during prolonged near tasks.
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