Sustained Accommodative Control in Young Adults: Minimal Change After Brief Digital Reading Across Small Font Sizes Under Photopic Room Illumination
DOI:
https://doi.org/10.56532/mjsat.v6iS1.780Keywords:
Digital Reading, Accommodation Response, Photopic Illumination, Font SizesAbstract
The action of ocular ciliary muscle contributes to the accommodation system, especially when the eye focuses on near objects. Sustaining clear near vision during reading requires precise accommodative control. Each change in viewing distance or target detail initially presents a blur stimulus, prompting the accommodation system to adjust lens power to restore retinal image clarity. This dynamic process is continually challenged by variable task demands, including changes in print size. This study compared the accommodation response with different font sizes before and after a near task with a digital device under photopic bright room illumination. Thirty young adults with a mean age of 22.13 ± 1.31 years completed 10 minutes of uninterrupted reading on an iPhone 11 at a fixed near viewing distance. The reading material consisted of black text on a white background with different font sizes of Arial letter equivalent to N5, N8, N10, and N12 under normal photopic room lighting. The dioptric value of accommodation response was measured objectively using an open field Grand Seiko WAM-5500 autorefractor, before and after the reading task. The accommodation response in baseline measurement before reading was 4.20 ± 0.63 D, after reading with N5 size was 4.13 ± 0.63 D, after reading with N8 size was 4.32 ± 0.34 D, after reading with N10 size was 4.39 ± 0.75 D, and after reading with N12 size was 4.55 ± 0.60 D. There was a statistically significant difference in accommodation response before and after reading task only for N12 font size (Wilcoxon signed-rank test: Z = -2.40, p = 0.02). It could be concluded that the action of the ocular ciliary muscle is well controlled for intense small-sized near targets. These findings indicated that the young adult eye responds similarly to small letter sizes after a short duration of reading under photopic room illumination.
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