Comparison of the Anterior Segment Optical Coherence Tomography and Ultrasound Biomicroscopy in the Evaluation of Patients With Angle Closure

Abstract

Purpose: : To compare anterior chamber angle findings using anterior segment optical coherence tomography (AS–OCT) and ultrasound biomicroscopy (UBM) in patients with angle closure.

Methods: : This was a prospective observational comparative study done at the National University Hospital of Singapore from August 2004 to May 2005. Patients with angle closure on gonioscopy were recruited from the glaucoma clinic to undergo imaging with the AS–OCT followed by UBM. Both AS–OCT and UBM imaging were performed by a single operator under uniform dark and light conditions that were standardised using a lux meter. In all eyes, the nasal, temporal and inferior angles were imaged. All images were analysed by an independent masked observer using custom software (Mathworks Inc., Natick, MA). The right eyes of the patients were used for analysis. Parameters analysed with both imaging techniques included angle opening distance at 500µm from the scleral spur (AOD500), angle recess area at 500µm and 750µm from the scleral spur (ARA500, ARA750), and trabecular–iris space area up to 500 µm and 750µm from the scleral spur (TISA500 , TISA750). Pearson’s correlation coefficient was calculated.

Results: : Moderate correlations were found between the AS–OCT and UBM in the nasal and temporal angles in both dark (R= 0.6–0.7) and light (R= 0.5–0.6) conditions. However, there was poor correlation between the 2 imaging techniques in the inferior angle (R= 0.2–0.4). Imaging of the inferior angle with the AS–OCT was more difficult, and produced images of a lower quality compared to the nasal and temporal angles.

Conclusions: : The AS–OCT and UBM show moderate correlation in the nasal and temporal quadrants, but dissimilar findings in the inferior quadrant. Possible explanations for this disparity include poor image quality in the inferior region with the AS–OCT, and positional factors (the AS–OCT is performed with the subject sitting up while UBM is performed with the subject lying supine). While AS–OCT has the advantages of being a non–contact, more rapid, and more comfortable imaging technique compared to the UBM, further research will be needed to determine the clinical use of application of this device.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior segment