Descriptive Analysis Of Angle Closure Using The Irido-Trabecular Contact Index Of Anterior Segment Optical Coherence Tomography

To assess the diagnostic ability of the irido-trabecular contact (ITC) index, measured by anterior segment optical coherence tomography (AS-OCT), in the evaluation of primary angle closure (PAC), compared with gonioscopy. To evaluate the agreement between the ITC index and gonioscopy. To determine the precision of the ITC analysis in the specific location of angle closure in the different quadrants.

Multicentre study.

Cross-sectional study. 135 eyes of 135 phakic subjects (age >30 years) were included: 76 with open angle and 59 with CAP or suspected CAP (SCAP). ITC analysis of the swept source AS-OCT CASIA2  and dynamic gonioscopy were performed.

PAC on gonioscopy (reference standard) was defined as non-visibility of the trabecular meshwork in ≥2 quadrants. From the automatic detection of the scleral spur, CASIA2 calculates the ITC index, which represents the percentage of the angle that is closed.

The mean age was 48.1 ± 18.8 years. The mean ITC index was 3.5±7.8% for eyes with open angle and 34.1±22.2% for eyes with PAC/PACS (p<0.001). The AUC was 0.88 (95% CI: 0.83-0.94), for an ITC cut-off point ≥20%; sensitivity: 93%; specificity: 84%. A false positive rate of 7.4% and a false negative rate of 7.4% were found. The overall Kappa statistic for a 2-quadrant definition of angle-closure was 0.70. Sectorial agreement was: inferior: 0.45; superior: 0.43; temporal: 0.48; nasal: 0.59

: The ITC index presented a good diagnostic ability for PAC, with a moderate agreement with gonioscopy. The sectorial analysis with this technology could provide further information about the presence of peripheral anterior synechiae in each quadrant.