Investigating the Effect of Caffeine and Alcohol on Pupil Dynamics

Summary

The goal of this study is to understand how caffeine and alcohol affect the ocular and physiological systems, especially how the pupil (the aperture in the colored part of the eye) responds to light. It will also test whether these changes can be used to detect recent caffeine or alcohol intake using a portable eye device.

The main questions it aims to answer are:

1. How does caffeine change pupil responses, eye movements, and other ocular and physiological measurements?
2. How does alcohol change these same ocular and physiological responses?
3. Are the effects of caffeine and alcohol different from each other?
4. Can these changes be used to accurately identify whether someone has consumed caffeine or alcohol?

Researchers will compare caffeine, alcohol, and a placebo (a look-alike drink with no active substance) to see how each affects the ocular and physiological outcomes.

Participants will:

1. Attend three separate sessions where they will consume caffeine, alcohol, or a placebo (in random order)
2. Undergo pupillary response evaluation using a handheld device that measures responses to different colored light stimuli
3. Have their eye movements analyzed
4. Have retinal and choroidal thickness, blood perfusion, and ocular oxygen levels measured
5. Have basic body measurements recorded (such as pulse rate and blood pressure)
6. Complete tests at multiple time points over 2 hours after consumption

The results of this study may help develop a quick and non-invasive way to detect recent caffeine or alcohol use for clinical and safety purposes.

Conditions

• Caffeine
• Alcohol
• Pupillary Response
• Eye Movements
• Optical Coherence Tomography
• Optical Coherence Tomography Angiography
• Physiological Responses

Interventions

OTHER

Placebo Comparator: Placebo

Participants receive a matched placebo tablet together with a non-alcoholic beverage identical in appearance and volume to the active conditions. A cornstarch-based formulation may be used for the placebo tablet. Beverage presentation is standardized to maintain blinding across study conditions. No active caffeine or alcohol is administered.

OTHER

Caffeine administration

Participants receive a single oral dose of caffeine (\~3 mg/kg body weight) administered in tablet form. The caffeine is given with a non-alcoholic beverage matched to study conditions. All procedures are performed under randomized, double-masked crossover design conditions.

OTHER

Alcohol (Ethanol)

Participants consume a standardized alcoholic beverage designed to achieve a target blood alcohol concentration of approximately 0.05%. A placebo tablet is administered alongside the beverage to maintain masking. All procedures are performed under randomized, double-masked crossover design conditions.

Sponsors & Collaborators

• Home Team Science & Technology Agency (HTX)

  collaborator UNKNOWN

• National University of Singapore

  lead OTHER

Principal Investigators

• Raymond P. Najjar, PhD · Department of Ophthalmology, National University of Singapore (NUS)

Study Design

Allocation

RANDOMIZED

Purpose

DIAGNOSTIC

Masking

TRIPLE

Model

CROSSOVER

Eligibility

Min Age

30 Years

Max Age

50 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-06-01

Primary Completion

2027-05-05

Completion

2027-11-05

Countries

• Singapore

Study Locations