Repeatability and Reproducibility of Macular Thickness Measurements Using Fourier Domain Optical Coherence Tomography

AIM To evaluate repeatability and reproducibility of macular thickness measurements in visually normal eyes using the Topcon 3D OCT-1000. METHODS Phase 1 investigated scan repeatability, the effect of age and pupil dilation. Two groups (6 younger and 6 older participants) had one eye scanned 5 times pre and post- dilation by 1 operator. Phase 2 investigated between-operator, within and between-visit reproducibility. 10 participants had 1 un-dilated eye scanned 3 times on 2 separate visits by 2 operators. RESULTS PHASE 1: No significant difference existed between repeat scans (p=0.75) and no significant difference was found pre- and post-dilation (p=0.54). In the younger group variation was low (95% limits +/- 3.62microm) and comparable across all retinal regions. The older group demonstrated greater variation (95% limits +/- 7.6microm). PHASE 2: For a given retinal location, 95% confidence limits for within-operator, within-visit reproducibility was 5.16microm. This value increased to 5.56microm for the same operator over two visits and to 6.18microm for two operators over two visits. CONCLUSION A high level repeatability, close to 6microm, of macular thickness measurement is possible using the 3D OCT- 1000. Measured differences in macular thickness between successive visits that exceed 6microm in pre-presbyopic individuals are therefore likely to reflect actual structural change. OCT measures are more variable in older individuals and it is advisable to take a series of scans so that outliers can be more easily identified.