Intra– and Inter–observer Variability in Retinal Thickness Measurements Using OCT 4

Abstract

Abstract: : Purpose: To assess the intra– and inter–observer variability of retinal thickness measurements using Optical Coherence Tomography (Zeiss, STRATUS OCT) equipped with the new version 4.0 software (OCT 4). Methods: A retrospective chart review identified 7 eyes of 6 subjects with macular edema and 6 eyes of 3 healthy subjects without macular pathology who had multiple measurements of macular thickness taken by 2 operators using OCT 4. A Fast Macular Thickness Map program generated six 6mm long OCT scans in a radial spoke pattern centered on the patient’s fixation point through a dilated pupil. All scans quantified retinal thickness in 9 ETDRS areas, including a central disc of 1000µm diameter, plus inner and outer rings of 3000µm and 6000µm diameters, respectively, both divided into four quadrants. Additionally, all scans quantified central foveal thickness, calculated as the average of the six measurements taken at the fixation point by the six OCT radial scans, and total macular volume at 6mm. Each eye with or without macular edema had undergone 3 measurements each, by two operators on the same day. Intra– and inter–observer variability in retinal thickness (at the 9 EDTRS areas, and the central foveal thickness) and volume (at 6mm) were assessed by using, among other statistical tools, repeatability and intra–class correlation coefficients (ICC). Results: In healthy patients without macular pathology, OCT 4 measurements of retinal thickness and total macular volume demonstrated very little intra– and inter–observer variability, and showed excellent reproducibility across all measurements. Larger intra– and inter–observer variability was seen in patients with macular edema, particularly in measurements of central foveolar thickness. Measurements of total macular volume showed less variability than retinal thickness across both patient groups. Conclusions: This pilot study suggests that OCT 4 can provide reproducible measurements of retinal thickness and total macular volume in both healthy patients and in patients with macular edema. Intra– and inter–observer variability appears to be significantly increased for measurements of retinal thickness in patients with macular edema, compared with subjects with normal macula and foveal contour. Total macular volume measurements may be subject to less variability across all patients. A larger study is necessary to quantify more accurately the variability present in OCT 4 measurements of retinal thickness.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • imaging/image analysis: clinical