Abstract
Purpose: :
To evaluate the reliability of manual measurements of choroidal thickness in normal subjects performed by experienced and newly trained readers of Cirrus High Definition Optical Coherence Tomography (HD-OCT) scans.
Methods: :
Thirty-three eyes of thirty-three healthy subjects with no visual complaints or ocular diseases underwent high definition 1 line raster Cirrus HD-OCT scanning as part of a comprehensive dilated ophthalmologic exam. Two experienced and two newly-trained readers measured the choroidal thickness at 500 µm intervals temporal and nasal from the fovea, up to 2000 µm for all eyes. The readers were blinded to each other’s readings and Reader-4 measured all eyes twice, the second time blinded to the identity of the scan and previous measurements. Intra-observer, inter-observer reliability statistics and intra-class correlation coefficients (ICC) were calculated using ANOVA analysis in SPSS (Version 18.0 for Windows, SPSS Inc, Chicago, IL, USA) and Bland-Altman plots in Prism 5.0 (Prism 5.0 for Mac; Graph Pad, San Diego, CA).
Results: :
The mean age was 51 ± 19 years (range: 23-78) and 52% were male. Mean choroidal thickness showed a pattern of thinnest choroid nasally, thickening in the subfoveal region and then thinning again temporally. The mean subfoveal choroidal thickness was 276 ± 75 µm. The inter-observer coefficient of reliability (CR) was 0.98 among all observers. Between experienced observers the CR was 0.95, and for each of two new readers versus the experienced readers the CR was 0.97 and 0.97. The ICC (confidence interval) for all observers was 0.93 (0.91-0.94). The experienced observers had an ICC of 0.91 (0.89-0.93) and for each new observer to the experienced observers 0.92 (0.90-0.93) and 0.92 (0.91-0.94). The intra-observer CR was 0.99 and the ICC was 0.98 (0.98-0.99). Bland-Altman plots showed agreement between the observers (Bias = 0.930), suggesting that the technique is reproducible.
Conclusions: :
The results of this study demonstrate high inter-observer and intra-observer correlation in measurements of choroidal thickness, particularly between newly-trained readers and experienced readers. This study suggests that choroidal thickness measurements in future studies can be reliably performed by readers with varying levels of experience.
Keywords: imaging/image analysis: clinical • choroid • clinical (human) or epidemiologic studies: systems/equipment/techniques