Ultrasound biomicroscopic comparison of primary open-angle glaucoma and primary angle-closure glaucoma eyes in dark and light conditions
Background: With the use of ultrasound biomicroscopy, we aim to look at differences in anterior segment parameters of eyes with primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) in dark and light conditions.
Methods: Ultrasound biomicroscopy was performed for 30 subjects with PACG and 30 subjects with POAG at initial presentation before any treatment. Measurements of angle opening distance (AOD-500 and AOD-750) and trabecular-iris space area (TISA-500 and TISA-750) 500 and 750 mm from the scleral spur in both dark and light conditions were made. Anterior chamber depth (ACD) and axial length (AL) were also measured.
Results: The mean age of PACG patients was 67.6 ± 9.6 years and POAG patients 62.1 ± 13.9 years. The mean ACD (2.70 ± 0.53mm) in PACG patients was significantly different from that (3.32 ± 0.52mm) of POAG patients (p<0.0001). There were also significant differences (p=0.0004) in the mean AL of PACG (22.91 ± 0.86mm) and POAG (24.47 ± 1.67mm) patients. Significant differences between POAG and PACG eyes were found for TISA-500, TISA-750, AOD-500 and AOD-750 in both light and dark conditions (p<0.001 for all). The light-dark differences in PACG eyes were smaller than that of POAG eyes for all AOD and TISA values in the inferior, superior, nasal and temporal quadrants. However, with the exception of AOD-750 in the inferior quadrant (p=0.0524), there were no significant differences in light-dark changes between POAG and PACG eyes for all parameters in the 4 quadrants.
Conclusions: Ultrasound biomicroscopy is a useful tool in the diagnosis and management of glaucoma. We found significant differences in mean AL, ACD, TISA-500, TISA-750, AOD-500 and AOD-750 between PACG and POAG eyes. However, there were no significant differences between PACG and POAG eyes in terms of light-dark difference in anterior segment parameters, except for AOD-750 in the inferior quadrant. Further evaluation of the above findings could be done in future with a larger population.