Though invaluable in posterior segment imaging, OCT is less definitive when assessing angle closure, according to a new study in the British Journal of Ophthalmology. Researchers evaluated 2,027 subjects (with no relevant ocular history) using both swept-source anterior segment OCT and traditional gonioscopy, and found the two approaches provided different anterior chamber dimensions, leading to false positive angle-closure diagnoses based on the OCT readings.

Using an angle-closure definition of iridotrabecular contact of ≥35%, ≥50% and ≥75% of the circumferential angle, the team found OCT incorrectly identified 14.7% of the angles as closed when the angle measured ≥50% of the angle was closed. Both OCT and gonioscopy revealed these false positive eyes still had significantly wider and deeper anterior chambers compared with the correctly identified angle-closure eyes.

The researchers noted a deeper anterior chamber depth and a lower lens vault were both significantly associated with false positives on OCT—more than half of the false positive eyes had short iridotrabecular contact and 39% had irregular contact, they noted in their study. 

Porporato N, Baskaran M, Tun TA, et al. Understanding diagnostic disagreement in angle closure assessment between anterior segment optical coherence tomography and gonioscopy. Br J Ophthalmol. September 6, 2019. [Epub ahead of print].