The goal of the study is to determine the effect of different doses of caffeine on intraocular pressure. We hypothesized that higher dosage of caffeine would increase intraocular pressure more than lower doses.

Eligible subjects will be randomized into three groups:

1. group 1: intake of decaffeinated coffee
2. group 2: intake of coffee with lower caffeine dose
3. group 3: intake of coffee with higher caffeine dose

Intraocular pressure will be measured at 0, 30, 60 and 90 minutes after coffee intake.

decaffeinated coffee contains 0.5-2 mg of caffeine regular dose coffee contains 91.8 mg of caffeine high dose coffee contains 144 mg of caffeine

all three groups' intraocular pressure will be measured with the Goldmann applanation tonometer at 4 timepoints:

1. 0 minutes (baseline)
2. 30 minutes after intake
3. 60 minutes after intake
4. 90 minutes after intake

Inclusion Criteria:

• healthy subjects
• normal central corneal thickness
• normal baseline intraocular pressure

Exclusion Criteria:

• any ocular disease
• baseline intraocular pressure over 21 mmHg
• central corneal thickness less than 520 microns or more than 540 microns