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Intra-observer and inter-observer repeatability of anterior eye segment analysis system (EAS-1000) in anterior
Andrew K C Lam1, Rufina Chan, George C Woo
1Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, China. orkclam@polyu.edu.hk
Background:
Anterior chamber configuration can be assessed via optical or ultrasonic techniques. Scheimpflug photography is a non-invasive method measuring the anterior segment. The Anterior Eye Segment analysis system, EAS-1000, utilises the Scheimpflug principle and was found to have good repeatability. Previous repeatability studies, however, have had limitations in their design. The current study investigated the intra-observer and interobserver repeatability of the EAS-1000.
Methods:
Twenty-five healthy young subjects were recruited. The anterior chamber angles in different quadrants were measured by two examiners for interobserver analysis. The first examiner repeated the measurement at another session for intra-observer analysis. The 95% limits of agreement and intra-class correlation coefficient (ICC) were calculated. The anterior chamber depth was also measured and compared with ultrasound biometry.
Results:
The anterior chamber angle assessment demonstrated good intra-observer (ICC ranging from 0.77 to 0.90 for different quadrants) and interobserver (ICC ranging from 0.68 to 0.81 for different quadrants) repeatability. The 95% intra-observer limits of agreement were within +/-5 degrees. The 95% interobserver limits of agreement were within +/-6 degrees. There was no significant difference between male and female subjects or among angles at different quadrants. The anterior chamber depth was found to be repeatable (ICC > 0.90) with 95% limits of agreement +/-0.1 mm. The anterior chamber depth was shallower than that obtained from ultrasound biometry.
Conclusions:
The EAS-100 is a non-invasive instrument which is repeatable for measuring the anterior chamber angle and depth. It provides quick results and is good for screening purposes. There is an under-estimation of anterior chamber depth, as previously reported.