Determinants of Pupil Diameters and Pupil Dynamics in an Adult Chinese Population

Background: To investigate the determinants of pupil diameter (PD), amplitude of pupil diameter change (PD-change) and speed of pupil constriction (SPC) using video anterior segment optical coherence tomography (AS-OCT) in a population-based sample of Chinese adults.

Methods: Chinese adults aged 40 to 80 years who were free from glaucoma were consecutively recruited from the population-based Singapore Chinese Eye Study. The SPC was measured by AS-OCT videography. Univariate and multivariate analyses were performed to examine the effects of demographic and ocular biometric factors (e.g., axial length [AL], anterior chamber depth [ACD], baseline PD, iris thickness at the area of the dilator muscle [ITDMR], iris area [IA], and iris bowing [IB]) on SPC, PD, and PD-change.

Results: A total of 266/302 (89.5 %) AS-OCT videos of eligible eyes were available for analysis. Among these subjects, 64.3 % were women, and the mean age (± standard deviation [SD]) was 56 ± 8.3 years. SPC was not associated with sex. In multiple regression analyses, SPC was independently associated with baseline PD (β = 0.116, p = 0.006). Baseline PD was independently associated with ACD (β = 0.341, p < 0.001), TISA 500 (β = -4.513, p < 0.001), IA (β = -2.796, p < 0.001), and ITDMR (β = 6.573, p < 0.001). PD-change was independently associated with ACD (β = 0.256, p < 0.001), IA (β = -1.507, p < 0.001), IB (β = 0.630, p = 0.011), and ITDMR (β = 3.124, p < 0.001).

Conclusions: Among normal eyes in an adult Chinese population, SPC was associated with larger baseline PD. Larger baseline PD and greater PD change form dark to light were associated with greater ACD, with smaller IA and thicker ITDMR.