Baseline pupil size predicts dilation rate with 1% tropicamide in a young African population

Background: The use of ophthalmic topical agents is critical to the success of several ophthalmic diagnostic procedures, particularly posterior segment examination. Aim: This study investigated the relationship between age, gender, and anterior segment biometry and pupillary dilation dynamics using 1% Tropicamide ophthalmic solution in a young African population. Setting: The study took place at the School of Optometry eye clinic, University of Cape Coast, Ghana. Methods: A pre-test–post-test study design was utilised, involving 51 participants of Black African descent with dark irides, classified according to the Franssen reference set. Baseline anterior segment biometric parameters, including central corneal thickness (CCT), anterior chamber depth (ACD), and pupillary diameter (PD) of one randomly chosen eye, were measured using the Cirrus High Definition-Optical Coherence Tomography (HD-OCT) system. Following baseline assessment, a drop of 1% tropicamide was instilled in a randomly selected eye of each participant. Subsequent PD measurements were obtained at five-minute intervals over a 30-minute period using the Cirrus HD-OCT. All data collection took place in a dark room set up. Results: The mean baseline pupillary diameter (PD) was 4.31 ± 0.67 mm, with a total change of 2.00 ± 0.73 mm over 30 minutes. No significant correlations were found between the rate of pupillary dilation and age, anterior chamber depth (ACD), or central corneal thickness (CCT) (P > 0.05). However, the rate of dilation showed a significant negative correlation with baseline PD (r = –0.54, P < 0.001). Conclusion: Smaller baseline pupils dilated faster, indicating baseline pupil size may predict individual dilation dynamics for diagnostic or therapeutic applications. Contribution: The results of this study provide data that could optimise the use of tropicamide 1% for pupillary dilation in young African populations.