Biometric Measurement of Iridocorneal Angle Parameters in a Sample of Healthy Saudi Eyes

Abstract

Background: Iridocorneal angle (ICA) or anterior chamber angle is the anatomical structure responsible for aqueous humor outflow and regulating intraocular pressure inside the eye. Objective: The study aims to evaluate iridocorneal angle parameters in healthy Saudi eyes using the spectral domain located in the anterior segment optical coherence tomography (AS-OCT) and to describe their correlation with other factors. Methods: For precise measurements of ICA, anterior segment imaging was executed with the aid of spectral-domain AS-OCT MS-39®. The measurements of the iridocorneal angle included angle opening distance (AOD) and trabecular-iris space area (TISA), located 500 and 750 μm away from the actual scleral spur from nasal and temporal angles. Results: The comparison of temporal and nasal angle parameters showed significantly higher AOD500 values in the temporal compared to the nasal angle (p=0.005). The study also evaluated correlations with a grade of the angle, and no correlations were found between gender, refractive error, iris thickness, and angle parameters. Multiple linear regression with backward elimination of non-significant factors found age (p=0.002), angle grade (p<0.001), predicting factors for nasal AOD500 (Adjusted R2=0.772, p<0.001), and angle grade (p<0.001) and temporal iris thickness (p=0.004) predicting factors for temporal AOD500 (Adjusted R2=0.511, p<0.001). IOP (p =0.026) and angle grade (p<0.001) were found to predict factors for nasal TISA500 (Adjusted R2=0.639, p<0.001), and angle grade (p<0.001) and temporal iris thickness was found predicting factors for temporal TISA500 (Adjusted R2=0.314, p<0.001). Conclusion: AS-OCT is a valuable, easy, non-aggressive method to evaluate the iridocorneal angle.