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KMID : 1011420190240020143
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Journal of Korean Ophthalmic Optics Society
2019 Volume.24 No. 2 p.143 ~ p.152
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Changes of Binocular Vision Function in Eyes with Normal and Abnormal Visual Function according to Reading Devices
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Noh Hyun-Jin
Kim Hyun-Jin
Jung Jae-Young
Park Sang-Wook
Seo Han-Byul
Yu Hee-Ra
Choi A-Young
Park Mi-Jung
Kim So-Ra
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Abstract
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Purpose: In this study, changes of binocular vision function and differences in subjective symptoms in eyes with normal and abnormal visual function were investigated after completion of different reading tasks at the same distance.
Methods: Ninety-nine volunteers aged 18 to 31 years who had no ocular disease and corrected or uncorrected visual acuity of 0.8 or better were classified as normal or as having accommodative excess, accommodative infacility, or convergence insufficiency according to their visual function; a total of 33 volunteers were finally enrolled in this study.
They were asked to read a paper book and e-book using a tablet PC for 30 minutes under identical experimental conditions. Before and after reading tasks, their binocular vision function was assessed and subjective symptoms were evaluated by a survey using CISS questionnaires.
Results: Near point of convergence in eyes with normal visual function and accommodative infacility tended to be receded after reading, with the amount of reduction being greater after e-book reading. Near point of convergence in convergence insufficiency became significantly shorter; however, there was no difference between reading devices. Near heterophoria showed a tendency of eso-shift after e-book reading except for accommodative excess. There was no significant difference in AC/A ratio after paper book reading except for accommodative excess, while accommodative infacility and convergence insufficiency showed reduced AC/A ratio, and accommodative excess showed increased AC/A ratio after e-book reading. Negative relative convergence showed a tendency to increase after paper book reading regardless of visual function anomalies, while a tendency for decrease was observed after e-book reading. Positive relative convergence was further increased after e-booking reading except for accommodative excess. After e-book reading, the score of subjective symptoms was higher than that after paper book reading regardless of visual function anomalies; however, the characteristic subjective symptom varied according to the kind of visual function anomaly.
Conclusions: It was revealed that the change in binocular vision function was different according to the condition and environment of tasks even though the accommodative and convergent stimuli were identical, and the changing patterns also varied depending on the visual function anomaly, resulting in a difference in subjective symptoms. Therefore, careful attention is necessary when patients with visual function anomalies perform near tasks because changes in binocular vision function may be differently induced according to the task environment, and its effect on the degree and pattern of subjective fatigue may differ.
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KEYWORD
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Accommodative excess, Accommodative infacility, AC/A ratio, Binocular vision function, Convergence insufficiency, Fusional vergence, Near point of convergence, Phoria, Reading devices, Subjective symptoms
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