Influences of atmospheric pressure and temperature on intraocular pressure

PURPOSE. To determine whether the atmospheric pressure (ATM) change experienced during diving can induce changes in the intraocular pressure (IOP) of eyes in a normal population. METHODS. The IOP of 27 healthy volunteers (ages, 23.8 ± 4.9 years; range, 18-44) was measured with a Perkins applanation tonometer by two independent investigators who were masked to the previous measurements. Measurements were taken at baseline (normal ATM, 1 Bar and 24°C), at 28°C and 24°C after the ATM was increased to 2 Bar in a hyperbaric chamber, at baseline again, and finally at the normal ATM of 1 Bar but a temperature of 28°C. Multivariate regression analysis was used to evaluate the results. RESULTS. The mean IOP decreased significantly from 11.8 mm Hg in the right eye (RE) and 11.7 mm Hg in the left eye (LE) at 1 Bar to 10.7 mm Hg (RE) and 10.3 mm Hg (LE) at 2 Bar (P = 0.024, RE; P = 0.0006, LE). The IOP decrease remained constant during the ATM increase period (40 minutes) and was independent of the temperature change. The temperature increase alone did not significantly influence the IOP. CONCLUSIONS. An increase of the ATM to 2 Bar (equal to conditions experienced during underwater diving at 10 meters) modestly but significantly decreased the IOP independently of the temperature change. During the period of increased ATM (60 minutes), the IOP decrease remained stable and was independent of blood pressure change or corneal thickness.