Angle closure extent, anterior segment dimensions and intraocular pressure

Area of Science:

• Ophthalmology
• Anterior Segment Imaging
• Glaucoma Research

Background:

• Intraocular pressure (IOP) is a key risk factor for glaucoma.
• Accurate measurement and understanding of factors influencing IOP are crucial for diagnosis and management.
• Anterior segment dimensions play a role in regulating aqueous humor outflow and IOP.

Purpose of the Study:

• To investigate the association between iridotrabecular contact (ITC) and other quantitative anterior segment dimensions with intraocular pressure (IOP).
• To assess the predictive value of these parameters, individually and jointly, on IOP.
• To explore potential differences in these associations, particularly in specific demographic groups.

Main Methods:

• A cross-sectional study involving 2027 subjects aged ≥50 years.
• Swept-source optical coherence tomography (SS-OCT) was used to measure ITC index, angle opening distance (AOD), trabeculo-iris space area (TISA), anterior chamber depth (ACD), and other parameters.
• Statistical analysis included Lowess regression and generalized additive models to assess the relationship between anterior segment dimensions and IOP.

Main Results:

• An ITC index above approximately 60% was significantly associated with higher IOP.
• Anterior chamber depth (ACD) below 2.5 mm was also significantly associated with higher IOP.
• A combined model of ACD and ITC index was more predictive of IOP than individual parameters, especially in women with gonioscopically closed angles (R²=52.7%).

Conclusions:

• The extent of angle closure and ACD below specific thresholds are jointly associated with elevated IOP.
• These biometrical parameters, reflecting mechanical obstruction of aqueous outflow, contribute to increased IOP.
• The findings are particularly relevant for understanding IOP elevation in women with gonioscopic angle closure.