Alteration in anterior chamber depth and volume following postural change from upright to right and left lateral decubitus positions

Abstract

 

Purpose

 

We performed a prospective observational study to determine the response of anterior chamber (AC) parameters following postural change from upright to right lateral decubitus (RLD) and left lateral decubitus (LLD) position over a 1-hr period in healthy adults.

 

Methods

 

Anterior segment tomography (AST) was performed bilaterally using the Oculus Pentacam® on 15 normal adults in a seated upright position. The subject was then randomly placed in a RLD or LLD position for 1-hr. after AST was repeated while the subject remained in the lateral position. All subjects returned on a separate date to repeat the procedure on the opposite side. Analyzed parameters included anterior chamber volume (ACV), central anterior chamber depth (CACD), and peripheral anterior chamber depth (PACD) at 6mm, 8mm, and 10mm eccentricity in 4 principle meridians (superior, inferior, nasal, temporal). Statistical analysis was performed using paired, 2-tailed t-test and assuming 90° rotation.

 

Results

 

Average age (±SD) was 34±12.5 years (range 23-58). 13 subjects were female and 2 were male. In order of decreasing depth, the upright mean PACDs at 6mm eccentricity were 2334±323µm temp., 2143±353µm inf., 1833±344µm sup., and 1765±302um nasally (Fig. 1). There was no difference in AC parameter change in dependent and non-dependent eyes between the RLD and LLD positions. There was a significant decrease in the ACV and CACD in dependent eyes (mean -5.73mm³ p < 0.001, -17µm p=.05) and non-dependent eyes (-3.87mm³ p=.01, -14 µm p<.05). In dependent eyes, there was a significant decrease in the inf. PACD at 6mm (-96µm p<.001) and 8mm (-233µm p<.001) eccentricities and the temp. PACD at 6mm (-95µm p=.01), 8mm (-182µm p<.001), and 10mm (-88µm p=.01) eccentricities. Interesting there was an increase in the sup. PACD at 6mm (+105µm p=.01) and 8mm (+125µm p<.01) eccentricities. In the non-dependent eyes, there was a significant decrease in the temp. PACD at all eccentricities (6mm: -186µm p< 0.001, 8mm: -275µm p< 0.001, 10mm: -176µm p<.001).

 

Conclusions

 

There is a significant decrease in ACV and CACD bilaterally after assuming a lateral decubitus position for 1 hr. These changes are similar between RLD and LLD positions. The decrease in PACD appears to be localized to the inferior/temporal quadrants. Further research is needed to determine if this AC shallowing contributes to IOP elevation.  

 

Fig. 1

 

 

Fig. 2