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A novel iridocorneal-angle imaging system (Gonioscope) has been introduced which can provide full 360 degree angle photos in order to provide standardized gonioscopy. Our goal was to acquire and compare the ACA parameters from 2 different methods using angle photos from this newly introduced angle imaging system vs ASOCT-derived angle images.
Twenty five eyes from 16 normal participants and 29 eyes from 16 glaucoma patients imaged with the Gonioscope (GS-1, Nidek) and ASOCT (Zeiss Cirrus 5000). With the GS-1, 360 ACA images were taken in all eyes. In ASOCT, at least one 5-line raster image set were taken at the ACA at four different locations (3, 6, 9, and 12 o’clock). In ASOCT, the angle openings were evaluated of the angle open distance under the Schwalbe’s line(AOD-SL) and Trabecular-Iris Space Area under the Schwalbe’s line (TISA-SL). In GS-1, the angle openings were evaluated at four quadrants using the Shaffer system. Spearman’s correlation was performed to assess correlation between AOD-SL/TISA-SL and Shaffer grade.
Of the total 187 quadrants, 178 quadrants with both high quality AS-OCT image and Gonioscope images were analyzed, and only 9 were excluded due to poor image quality. A strong correlation was found between AS-OCT parameters and the objectively derived gonioscopic Shaffer grades. Correlation coefficients between AOD-SL/TISA-SL and Shaffer grade were 0.749 and 0.741, respectively. Specifically, the correlations in the horizontal quadrants (AOD-SL 0.769, TISA-SL 0.761) were stronger than that in the vertical quadrants (AOD-SL 0.730, TISA-SL 0.726). The correlations in patients (0.697 AOD-SL and 0.67 TISA-SL) were stronger than that in the normal participants (0.559 AOD and 0.567 TISA).
Objective evaluation of the iridocorneal angle, either with ASOCT or using the newly-introduced 360-degree angle imaging system (Gonioscope), needs to be investigated further as these imaging systems may have potential utility in glaucoma screening programs.