Peripheral Anterior Synechiae, Angle Closure and Angle Width - A Comparison Study Using the Anterior Segment OCT

Abstract

Purpose:: To evaluate the relationship between angle width determined by anterior segment optical coherence tomography (AS-OCT), the presence of peripheral anterior synechiae (PAS) and gonioscopy grading.

Methods:: Images of the nasal, temporal and inferior angles of the right eye of every subject were obtained with AS-OCT. The angle opening distance (AOD), trabecular-iris space area (TISA), and area of recessed angle (ARA) in the nasal, temporal and inferior quadrants measured 500µm and 750µm from the scleral spur were calculated. Gonioscopy was performed for each quadrant to determine the Shaffer grade and presence of PAS. PAS was defined as abnormal adhesions of the iris to the angle that were at least half a clock hour in width and present to the level of the anterior trabecular meshwork or higher. Angle closure was deemed to be present if Schwalbe’s line was not visible on gonioscopy in at least 2 quadrants (ie. Shaffer grade 0).

Results:: A total of 203 subjects were recruited, of which 123 (60.6%) subjects were female. 59 (28.9%) eyes had angle closure while 81 (39.9%) had PAS. The mean values of AOD, TISA, and ARA in the nasal, temporal and inferior quadrants were significantly less in eyes with PAS compared to those without PAS (p<0.001). Analysis by quadrant showed that these parameters were also less in the nasal and temporal quadrants in eyes with PAS (p<0.01). AOD, TISA and ARA were significantly correlated with clock hours of PAS (Pearson’s correlation coefficient 0.24, 0.31 and 0.17 respectively, p<0.05) and Shaffer grading of angle width (Spearman’s correlation coefficient 0.70, 0.59 and 0.58 respectively, p<0.01). The mean values of AOD, TISA and ARA in the 3 quadrants was significantly less in eyes with angle closure compared to eyes without angle closure (p<0.001). Analysis by quadrant also showed all parameters were less in each quadrant in eyes with angle closure. (p<0.01)

Conclusions:: Angle width determined using AS-OCT was significantly reduced in eyes with PAS and eyes with angle closure. There was a significant correlation between angle width and degree of PAS; angle width and Shaffer grading were also significantly correlated.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior chamber • imaging/image analysis: clinical