Dynamic and Static Pupil Changes After Near Work: Comparison Between Reading a Book and Using a Smartphone

OBJECTIVES: Decreased static pupil size due to accommodation is a common clinical finding; however, changes in pupillary dynamic responses after near-work activities such as reading a book and using a smartphone are not well understood.
METHODS: The present study was performed on 76 right eyes of 76 volunteers (mean age: 20.95±2.34 years) who had ocular near activity more than 4 h per day. The participants were divided into two groups based on the dominant activity, reading a book (Group 1) or using a smartphone (Group 2). Evaluation of dynamic and static parameters of the pupil was performed before and after 1 h of continuous routine eye activity in both groups and compared.
RESULTS: Near work reduced pupil diameter (PD) in all static components (p<0.001) and the amount of change in the min PD (p=0.039) and mesopic PD (p=0.043) were different between two groups and were higher in Group 1 (both, p<0.05). Dynamic elements showed a decrease in initial diameter, amplitude and velocity of contraction and dilation, and an increase in other components so that the changes after using smartphone were significant in all dynamic parameters (all, p<0.05), but reading the book only made a significant difference in the initial diameter, amplitude, and velocity of contraction and duration of dilation (all, p<0.05); the changes were only different in the initial diameter between the two studied groups, which was higher in Group 1 (p=0.047).
DISCUSSION AND CONCLUSION: The present study showed that reading a book and using smartphone cause changes in the pupil compo-nents, which were decreasing in diameter components and velocity of changes and increasing in latency of changes; the type of ocular work may affect the changes.