Influence of Body Position in Intraocular Pressure and Lens Vault in Healthy Eyes

Abstract

Purpose : Changes in body position from upright to supine are known to be associated with a rise in intraocular pressure (IOP). In this study of healthy eyes, we investigate position-related changes to anterior chamber morphology, in particular lens vault.

Methods : Fourteen eyes were recruited for this prospective, IRB-approved study. The participants were asked to remain seated for 10 minutes and then had their baseline IOP measured with a pneumatonometer followed by anterior segment OCT. The subjects then assumed a supine position for 10 minutes again followed by IOP measurement and anterior segment OCT. OCT images were taken with the Spectralis HRA+OCT (Heidelberg Engineering GmBH) using the two-angle anterior segment horizontal scan centered on the pupil (ART = 60). To image in multiple positions, the Spectralis FLEX module was used. The FLEX module is a modified surgical boom arm that orientates the Spectralis for imaging in nearly any body position. For image analysis, lens vault was defined as the perpendicular distance between the anterior pole of the crystalline lens to a horizontal line joining the 2 scleral spurs, on horizontal anterior-segment OCT B-scans. Anterior chamber width was also calculated and defined as the horizontal distance between the two scleral spurs. Statistical analysis was used to evaluate positional changes in intraocular pressure and lens vault.

Results : The mean age was 36.5±5.6 years. The spherical equivalent of the eyes was -2.5±1.3. IOP measured in the seated position was 17.65±2.7 mm Hg, and 23.2±2.2 mm Hg when the subjects were in a supine position (p = 0.01). Lens vault was -28.14±176.265 µm in the seated position and -258.93±251.54 µm in the supine position (p = 0.04). There was no statistically significant difference between two positions for the anterior chamber width (p=0.3).

Conclusions : Comparison of positional variations in anterior chamber anatomy as measured by OCT has recently become possible with the advent of the FLEX module. This study found that both IOP and positional changes in anterior chamber anatomy can occur in normal healthy eyes. Understanding normal positional anatomic changes may provide new insights into disease pathophysiology.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.