Limbus-insertion distance of superior rectus in primary angle closure glaucoma: an anterior segment OCT study

To compare the distance from the corneoscleral limbus to the insertion site of the superior rectus of primary angle-closure glaucoma (PACG) patients with normal controls and to identify potential characteristics associated with limbus-insertion distance.Cross-sectional study.A total of 92 subjects (eyes) were enrolled in the study: 35 were nonglaucoma controls and 57 were PACG patients.The limbus-insertion distance of the superior rectus was measured by anterior segment optical coherence tomography (AS-OCT) and intraoperative surgical caliper. The anterior chamber parameters were also measured using AS-OCT to identify potential characteristics associated with limbus-insertion distance.The limbus-insertion distance of the superior rectus was 0.40 ± 0.08 mm shorter in the PACG group than in the normal control group (p0.001). Anterior segment parameter values, including anterior chamber depth (ACD), anterior chamber width (ACW), anterior chamber area (ACA), and anterior chamber volume (ACV), were smaller in the PACG group than in the normal control group, but the lens vault was larger (all p0.001). A shorter limbus-insertion distance of the superior rectus was significantly associated with shorter axial length and "crowded" angle (smaller ACD, ACW, ACA, and ACV) (all p0.05).This is the first study to demonstrate that the limbus-insertion distance of the superior rectus was shorter in PACG eyes than in normal eyes. The shorter limbus-insertion distance may be another anatomic characteristic of PACG eyes.