Effect of Lateral Decubitus Body Posture on Anterior Chamber Angle in Healthy Subjects: An Anterior Segment Optical Coherence Tomography Study

Abstract

Purpose: To investigate the effect of the lateral decubitus (LD) position on the anterior chamber (AC) angle in healthy subjects. Materials and Methods: Twenty-three healthy young subjects were included in this prospective observational study. We measured AC angle parameters in the sitting and the left LD positions using anterior segment optical coherence tomography (Visante OCT): trabecular-iris angle (TIA), angle opening distance (AOD(500)), trabecular-iris space area (TISA(500)), anterior chamber width, lens vault, and anterior chamber depth. The Wilcoxon signed-rank test was used to compare the parameters between different body positions. Interobserver reproducibility of AC angle measurements was assessed by intraclass correlation coefficients. Results: Postural alterations from sitting to the left LD position significantly reduced the AC angle on the temporal side in right eyes (TIA: 39.53 +/- 2.38 to 38.31 +/- 3.47 degrees; AOD(500): 0.72 +/- 0.13 to 0.65 +/- 0.08; TISA(500): 0.25 +/- 0.06 to 0.22 +/- 0.04; all P < 0.05), whereas no significant changes were noted on the nasal side. Contrastingly, a significant decrease in the AC angle on the nasal side was noted for left eyes (TIA: 39.49 +/- 2.24 to 38.17 +/- 2.76 degrees; AOD(500): 0.68 +/- 0.09 to 0.64 +/- 0.10; TISA(500): 0.23 +/- 0.04 to 0.21 +/- 0.03; all P < 0.05). Anterior chamber width and anterior chamber depth were unaffected by postural alterations, but lens vault significantly was reduced following a shift to the left LD position. Conclusions: The AC angle parameters on the nondependent side of the eye in the LD position were significantly reduced compared with those in the sitting position. Therefore, postural shift from sitting to the LD position may induce alterations in the AC angle.