Abstract
Purpose:
We conducted this study to investigate how changing recumbent postures among supine, lateral decubitus, and prone with head turn positions influences intraocular pressure (IOP) in healthy subjects, and to assess how ocular perfusion pressure (OPP) changes in such postural alterations of body and head.
Methods:
This study included twenty healthy young Korean subjects. IOP and blood pressure measurements were taken with the subjects in the sitting position and the recumbent positions including supine, right lateral decubitus, left lateral decubitus, prone with right head turn, and prone with left head turn positions. IOP was measured using Icare® tonometer in both eyes 5 minutes after assuming each position in a randomized sequence. OPP was calculated using the formulas based on the mean blood pressure adjusted for the height of the eye over the heart. The eye on the lower side in the lateral decubitus or prone-with-head-turn position was termed as a dependent eye. Main outcome measures were difference in IOP and OPP of the dependent and non-dependent eyes during changes of sleeping positions of body and head.
Results:
Mean IOP of right and left eyes while sitting was significantly lower than that measured in each recumbent position (all, P<0.001). OPPs in both eyes were significantly higher in all recumbent positions than in sitting position (all, p<0.001). Mean IOP of the dependent eyes was higher than that of the non-dependent eyes in the lateral decubitus positions, and also in the prone positions with head turns (all, P<0.001). No significant inter-eye difference in OPP was found in all the positions. Compared among IOPs measured in the recumbent positions, mean IOP of the dependent eye in the lateral decubitus position or in the prone position with head turn was significantly higher than that of the ipsilateral eye in the supine position (all, P<0.001).
Conclusions:
All sleeping positions of head and body resulted in an elevation of IOP and an increase in the calculated OPP compared with the sitting position in healthy young subjects. The postural change from supine to lateral decubitus or prone-with-head-turn position increased IOP of the dependent eyes without significant alteration in OPP in healthy awake subjects. Further research is needed under nocturnal conditions in a sleep laboratory.
Keywords: 568 intraocular pressure