Abstract:
It is purported that caffeine, an
autonomic stimulant, affects visual
performance. This study sought to assess
whether caffeine intake was associated with
changes in pupil size and/or amplitude of
accommodation.
Patients and methods A double-masked,
crossover study was conducted in 50 healthy
subjects of age range 19 to 25 years.
Subjects were randomized to treatments
such that subjects consumed either 250 mg
caffeine drink or vehicle on separate days.
Amplitude of accommodation was measured
by the push-up technique, and pupil size
using a millimeter ruler fixed to a slit
lamp biomicroscope in dim illumination
(5 lux). Amplitude of accommodation
and pupil size were taken at baseline,
and at 30, 60 and 90 min time points post
treatment. Repeated measures one-way
ANOVA and paired t-test were used in
analyzing data.
Results Amplitude of accommodation and
pupil size after caffeine intake were
significantly greater than vehicle (Po0.001)
at each time point. Consumption of the
caffeine beverage was associated with
significant increases in amplitude of
accommodation and pupil size with time
(Po0.001). Amplitude of accommodation
rose from 12.4 (±2.2 D) at baseline to 15.8
(±2.6 D) at 90 min. Similarly, pupil size
increased from 3.4 (±0.4 mm) at baseline to
4.5 (±0.72 mm) at 90 min. Consumption of
vehicle was not associated with increase in
amplitude of accommodation or pupil size
with time.
Conclusion Pupil size and accommodation
are affected after ingestion of caffeine.
This study suggests caffeine may have some
influence on visual functions.
