Objective: To identify potential structural predictors for malignant glaucoma (MG) using ultrasonic biomicroscopy (UBM) images in primary angle-closure glaucoma (PACG) eyes.

Methods: This study enrolled 99 MG inpatients (110 eyes) from 1 January 2014 to 30 June 2024 in Shanghai Eye & ENT Hospital of Fudan University. Based upon surgical methods, the MG patients were divided into the trabeculectomy-MG group (70 eyes) and the phacoemulsification-MG group (40 eyes). PACG patients who did not develop MG were 1:1 matched to MG patients as controls. Preoperative information was collected, and four novel parameters were measured on UBM images, namely Sc-vz (the area enclosed by ciliary body and vitreous zonule), Hc-vz (the height of Sc-vz), Zmin (the length of the shortest zonule) and sCLD (simulated cilio-lenticular distance).

Results: Compared to PACG patients without MG, MG patients exhibited shorter axial length (AL), shallower anterior chamber depth (ACD) and smaller trabecular ciliary process angle (TCPA). Additionally, patients with MG exhibited shorter Zmin and sCLD, as well as smaller Sc-vz and Hc-vz than patients without MG, regardless of the surgical method. Zmin, sCLD, Sc-vz and Hc-vz demonstrated significantly higher predictive power than AL, ACD and TCPA. The combination of the four parameters reliably predicted MG with a sensitivity of 88.9% and a specificity of 76.5%.

Conclusions: PACG eyes with a shorter cilio-lenticular distance and a narrower ciliary body-to-vitreous zonule area are more likely to develop malignant glaucoma. Four novel UBM-measured parameters performed well in the prediction of malignant glaucoma either alone or in combination.