Correlation between intraocular pressure and body mass index in the seated and supine positions

Purpose: Examine the relationship between intraocular pressure (IOP) and body mass index (BMI) in the seated and supine positions. Patients and Methods: A prospective observational study was conducted in which the IOP was measured with a Tono-Pen (Reichert Inc., Depew, NY) in seated and supine positions in eligible participants with a wide range of BMI (18 to 70 kg/m²). The paired t test was used to compare seated to supine IOP. Stepwise regression analyses were used to investigate the correlation between IOP and BMI at these positions after adjusting for confounding variables of increased IOP, including age, race, mean arterial blood pressure, and central corneal thickness (μm). Results: The mean sitting IOP (16.3±2.9 mm Hg) was statistically lower than the mean supine IOP (17.7±3.1 mm Hg; P<0.0001). For each 10 unit increase in BMI, there was an increase of 0.55±0.23 mm Hg (P=0.0184) in IOP in the seated position and an increase of 0.49±0.24 mm Hg in IOP in the supine position (P=0.0409). BMI did not have a significant effect on the amount of increase in IOP observed in changing from the seated to supine position. Conclusions: Higher BMI is correlated with higher IOP in both the seated and supine positions. However, BMI has no significant effect on the amount of increase in IOP observed in changing from the seated to supine position.