Racial Differences and Anatomical Risk Factors in Narrow Angle Glaucoma: Insights from Ultrasound Biomicroscopy

Background: Glaucoma encompasses a range of diseases characterized by optic disc cupping resulting from the degeneration of retinal ganglion cells and optic nerve axons, leading to vision loss. Narrow-angle glaucoma (NAG) occurs when there is appositional or synechial closure of the angle between the iris and cornea, which can obstruct the outflow of aqueous humor, resulting in increased intraocular pressure (IOP) that damages the optic nerve. This study aims to investigate the relationships between patient demographics, lens vault, and anterior chamber angle measurements among patients with anatomic narrow-angles (ANA) or primary angle-closure suspect (PACS) using Ultrasound Biomicroscopy (UBM). Methods: This retrospective clinical study included 67 participants. UBM images were acquired using the ABSolu A/B/S/UBM Ultrasound Platform from Quantel Medical. Data were collected via a thorough chart review in the electronic medical record (EPIC) and included demographic information such as age, gender, race, intraocular pressure, vision, refractive error, family history of glaucoma, systemic hypertension, and diabetes. Descriptive statistics and mixed models were used for UBM measurements for each eye nested in each participant, adjusted by age, sex, presence of hypertension, and type 2 diabetes. Races were contrasted with Dunnett (control was white) in the mixed model with the same adjustments. Results: The mean age was 65.4 years (SD = 8, range 39–91), with 34% females (23/67). The racial distribution was 43% white, 13% African American, 27% Asian, and 16% other. Hypertension was present in 64% and type 2 diabetes (T2D) in 27%, with a 26% concordance for both conditions. Lens vault >0.5 was associated with 8 of 19 UBM measurements, such as anterior chamber depth (ACD), superior and inferior anterior chamber angle (ACA), superior angle opening distance (AOD) 500 and 750, superior angle recess area (ARA) 500, and superior trabecular-iris space area (TISA) 750. African Americans had larger values for superior and inferior ciliary body thickness (CBT) and lower values of inferior AOD 750. ‘Other’ classified races had larger values for superior ACA and lower superior IT750. A paired t-test comparing lens vault measurements between the right eye (OD) and left eye (OS) showed no significant difference (p = 0.27). Conclusion: This study reveals significant associations between higher lens vault and narrower anterior chamber angles and shallower anterior chamber depth. Additionally, it uncovers notable racial differences in UBM measurements, with African Americans generally having narrower angles and thicker irises. These findings could have implications for understanding racial disparities in eye conditions like angle-closure glaucoma. Early detection and treatment of narrow-angle glaucoma may prevent or delay the progression of the disease and preserve vision.