Iridocorneal Angle Assessment After Laser Iridotomy With Swept-source Optical Coherence Tomography

Abstract

To investigate the reliability of anterior chamber angle (ACA) measurements in narrow angles and assess the effect of laser peripheral iridotomy (LPI) on these measurements using novel swept-source optical coherence tomography (SS-OCT) technology. In this prospective observational study, patients with gonioscopically narrow angles were enrolled and scheduled for prophylactic LPI. Twelve ACA sections were obtained in each eye using SS-OCT (ANTERION, Heidelberg Engineering, Germany) before and after Nd:YAG LPI. A built-in algorithm calculated ACA measurements after manual identification of the scleral spur and ACA recess. Eight ACA parameters were evaluated: ACA (ACA 500, ACA 750); scleral spur angle (SSA 500, SSA 750); angle opening distance (AOD 500, AOD 750); and trabecular iris space area (TISA 500, TISA 750). The effect of LPI was assessed for each parameter, both nasally and temporally. Ten patients (18 eyes) were enrolled (mean age, 61.8±13.6 y; 60.0% female individuals). On average, the ACA was wider nasally than temporally (P=0.004). LPI significantly widened the ACA (range, 26.7-29.4%; P<0.05). ACA 500 increased by 29.4% (P<0.001), ACA 750 by 29.2% (P=0.002), SSA 500 by 27.3% (P=0.003), SSA 750 by 28.1% (P=0.001), AOD 500 by 28.6% (P=0.009), AOD 750 by 28.6% (P=0.003), TISA 500 by 27.3% (P=0.004), and TISA 750 by 26.7% (P=0.200). SS-OCT ANTERION imaging can be used to reliably measure ACA before and after LPI. ACA, AOD, SSA, and TISA are all valid ACA measurement methods.