Anterior segment features in neovascular glaucoma: An ultrasound biomicroscopy study

Abstract

Purposes: To investigate the features of the anterior segment structures in neovascular glaucoma (NVG) and analyze its differences from primary angle-closure glaucoma (PACG).

Methods: This study included patients who were first diagnosed with monocular NVG and PACG at the Affiliated Eye Hospital of Nanchang University during August 2019 to June 2022. Ultrasound biomicroscopy (UBM) was used to measure the anterior segment parameters of those eyes, including anterior chamber depth (ACD), anterior chamber width (ACW), anterior chamber area (ACA), iris area (IA), maximum iris thickness (IT_MAX), middle iris thickness (IT_MID), iris curvature (IC), lens vault (LV), angle opening distance (AOD₅₀₀), trabecular iris angle (TIA₅₀₀), trabecular-iris space area (TISA₅₀₀) and peripheral anterior synechia (PAS) length.

Results: In this study, paired samples t-test showed that IA [1.170(0.324) mm²], IT_MAX [0.368(0.079) mm], IT_MID [0.280(0.062) mm] and IC [0.147(0.037) mm] of NVG were smaller than F-NVG [2.058(0.195) mm², 0.611(0.045) mm, 0.415(0.049) mm and 0.272(0.077) mm], the AOD₅₀₀, TIA₅₀₀, and TISA₅₀₀ of NVG were also smaller than F-NVG. Independent samples t-test showed that ACD [2.349(0.350) mm] and ACA [16.326(3.547) mm²] of NVG were larger than PACG [1.971(0.240) mm, 12.030(1.860) mm²], but the IA [1.170(0.324) mm²], IT_MAX [0.368(0.079) mm], IT_MID [0.280(0.062) mm], IC [0.147(0.037) mm] and LV [0.436(0.172 mm)] were smaller than PACG [1.740(0.294) mm², 0.548(0.084) mm, 0.404(0.065) mm, 0.283(0.060) mm and 0.737(0.196) mm]. Among the 16 patients with 360° angle-closure NVG, the PAS length was 0.834 (0.326) mm, which exceeded the Schwalbe line.

Conclusion: In NVG, the iris is atrophied, thinned, and straight, while the ACD is normal or slightly shallow. In 360° angle-closure NVG, the PAS length exceeds the Schwalbe line, presenting a pseudo angle phenomenon and a hockey stick sign. Notably, the anterior segment structure morphology of NVG exhibit differences from those of PACG.

Keywords: Neovascular glaucoma; anterior segment; ultrasound biomicroscopy.