Reproducibility of Anterior Chamber Angle Measurements With Anterior Segment Coherence Tomography

Abstract

 

Purpose:

 

To study the reproducibility of iridocorneal angle (ICA) measurements with the standard Visante anterior segment optical coherent tomography (AS-OCT) in expert and non-expert observers.

 

Methods:

 

In twenty-three healthy subjects (medical students, 23 ± 1.9 years of age) five AS-OCT enhanced anterior segment single scans were taken in the 0-180 meridian of right eyes. After manually applying the ICA tool on the scleral spur (figure 1), the angle opening distance (AOD) and the trabecular iris surface area (TISA) were generated at 500 and 750 µm for all 115 scans at both nasal and temporal sides by two experts separately. Similarly subjects acted as non-experts and each analysed 5 scans of 4 randomly selected eyes (20 scans) after an extensive instruction. Variability of making and analysing an AS-OCT scan was determined using a random intercept model. Intra class correlations (ICC) were used as measures of intra/inter-observer reliability and internal consistency.

 

Results:

 

AOD and TISA data from nasal and temporal side of the anterior chamber did not differ significantly, so average data per eye were taken for further analysis. Technical replications did not significantly differ from each other. Mean coefficient of variation in expert 1 was 11.0% ± 1.3 for all parameters together, ranging from 9.7% to 12.8%. For expert 2 this was 10.4% ± 1.2, ranging from 9.2% to 12.1%. Mean ICC is 0.875 ± 0.021 in expert 1 and 0.942 ± 0.033 in expert 2. In non-experts coefficient of variation ranged from 5.6% to 17.6%, mean 10.2% ±1.3.

 

Conclusions:

 

Overall the reproducibility of the ICA measurements using the build-in Visante AS-OCT tool is good. The mean values of reproducibility showed to be very similar between experts and non-experts. The lower results of inter-observer variation, but good results in intra-observer suggest that non-experts have to undergo extensive instruction before analysing AS-OCT scans routinely.  

 

Keywords: anterior chamber • imaging/image analysis: clinical • trabecular meshwork