Anterior chamber angle measurement with Anterior Eye Segment analysis system Nidek EAS-1000: improving the repeatability.

Abstract

Previous studies have reported good intraobserver and interobserver repeatability of anterior chamber angle (ACA) assessment using the Anterior Eye Segment analysis system, EAS-1000. This study investigated the influence of fixation pattern, corneal plotting method and camera position on ACA measurements. A Nidek EAS-1000 system was employed for image acquisition and analysis, to obtain measurements of ACA. Twenty-five young healthy subjects participated. The ACAs were different in different quadrants and using different corneal plotting methods (Repeated measures 3-way anova, p < 0.05). However, the difference was <5 degrees and therefore not clinically significant. Alignment along the visual axis or optical axis did not yield any significant difference. Repeatability was improved by asking the subjects to fixate at the flashing light-emitting diode (LED). Temporal and nasal angles also demonstrated better repeatability than vertical angles. In measuring the vertical angles, the camera can be set at either the temporal or nasal side (Paired t-test, p > 0.05). The Anterior Eye Segment analysis system has good clinical repeatability in measuring ACA. It can be further improved with the use of the flashing LED during image acquisition.