Accommodation and pupillary response in the reading of texts with varying cognitive demand

Abstract

Abstract Purpose The relationship of the pupil size changes and lag of accommodation during reading of texts with varying cognitive demand was examined to determine whether the content of reading has significant influence on the accommodative and pupillary response. The results are discussed in regard to possible impact on myopia growth. Methods The study included 112 high school students (84 female, 28 male) aged 17 to 19. At the distance of 40 cm (=2.5 D) five short texts with different cognitive demands were presented on a laptop screen. From 1.0 m distance, the measurements of pupil size and accommodation were taken using the Plusoptix Power Refractor. Results Accommodative lag was found to be very stable during all the tests, with the mean value of 0.275 D. On the other hand, the pupil size varied significantly, depending on the mental effort and type of cognitive involvement. Smallest pupils were associated with the reading of advanced philosophically blended texts (4.79 mm), whereas texts with simple calculations were associated with greatest pupil size (5.08 mm). The difference between the these two was statistically significant with p = 0.0024. Conclusion Young subjects reading contents with higher cognitive demand, particularly those that require instant reasoning, have larger pupils than subjects reading philosophical novel‐like texts. Larger pupils are associated with more exaggerated aberrations and smaller depth of focus. With consistent lag of accommodation and considering accommodative microfluctuations, retinal image in this case must be blurrier or at least closer to the blur point. It can be concluded that the content of reading itself is a factor in nearpoint stress and could hipotetically contribute to myopia growth.