Abstract
Purpose:
The correlation between elevated intraocular pressures (IOP) and narrow anterior chamber angles is well documented. However, it is not well understood which parameters that describe the configuration of the anterior chamber angle most influence IOP. Previous studies of the angle have relied on gonioscopy grading as a means of defining how narrow an angle is. With anterior segment OCT, researchers can obtain more objective and reliable measurements of most angle parameters. While several studies have searched for a link between angle structure and IOP, these studies were either limited by the number of OCT images, few patients, or a limited scope of angle parameters. This study addresses these shortcomings in order to assess which angle parameters are most correlated with a patient’s baseline IOP, which is a fundamental step toward constructing a biomechanical model of the anterior chamber angle.
Methods:
We analyzed 8 OCT images from one eye of 63 patients with elevated IOP (upper 5% of IOPs) and 63 age-matched controls with IOPs in the normal range. All patients were from the Chinese American Eye Study (CHES), a population-based study of Chinese Americans in Los Angeles, CA. We analyzed the correlation between IOP and 17 different angle parameters by using a linear regression model to quantify the strength of the relationship.
Results:
Based on the linear regression analyses, IOP was inversely correlated (slope < -1.00) with angle recess area at 750 mm from the scleral spur (ARA750), anterior chamber depth (ACD), and anterior chamber area (ACA). IOP was directly correlated (slope > 0.70) with lens vault (LV) and pupillary diameter (PD). IOP was weakly correlated with some parameters such as ARA500 (absolute slope < 0.15). Similar relationships were present when the angle was divided into superior and inferior hemispheres. Additionally, many of these correlations were weak or absent in the control population, demonstrating that the relationship between level of IOP and size of angle structures is a non-linear one.
Conclusions:
Our results show that some angle parameters share a strong inverse or direct relationship with IOP. Other angle parameters are weakly correlated or uncorrelated with IOP. The strength of these relationships helps us identify and weight each parameter in the construction of a biomechanical model of the anterior chamber angle.