Association of caffeine intake with pupil size and visual acuity.

Abstract

OBJECTIVE: This research was done to check the association of dietary caffeine intake with pupil size and visual acuity. As caffeine itself is an autonomic stimulant drug and pupil size is controlled by smooth muscles of iris, stimulated by autonomic nervous system. Pupil size changes visual acuity by altering ocular aberrations.

METHODS: Caffeine consumers who drink coffee at-least 3 times per week or tea at-least 2 times per day were included in this comparative cross-sectional study. After taking their general history, pupil size was measured both in dim illumination and bright light conditions with the help of mm ruler and pen torch. Visual acuity for distance and near was assessed using logMAR (E-chart) and near acuity chart respectively. Mean values of dVA, nVA, PS(dim) and PS(illuminated) of caffeine consumers were compared to standard values of dVA(0.00) in logMAR , nVA(N=6.00), mean pupil size under dim light (6.00mm) and mean pupil size under bright light (3.00mm) respectively using One-Sample t Test.

RESULTS: Distance visual acuity (dVA) of caffeine consumers was significantly different from standard logMAR value(0.00) as p -value was 0.000, near visual acuity (nVA) of caffeine consumer was also significantly different from standard value (6.00) as p-value was 0.000. Similarly, mean pupil size under dim and bright light conditions of caffeine consumers were significantly different from mean of normal value of pupil diameter under dim and bright and light conditions respectively and p values were 0.001 and 0.000 for dim light pupil size and bright light comparisons with normal values mean respectively.

CONCLUSION: In habitual caffeine consumers near and distance visual acuity and pupil size for both dim and bright light conditions were different from the standard value of visual acuity and pupil size present in literature.