Purpose: To evaluate the in vivo repeatability and reproducibility of spectral-domain optical coherence tomography (SD-OCT) measurements of total retinal thickness (TRT) and retinal nerve fiber layer (RNFL) thickness in rats.
Methods: Retinal thickness was measured using an RNFL circular scan with AutoRescan and TruTracking modes in 20 eyes of Long-Evans Tokushima Otsuka rats. Three RNFL circular scan images were acquired with a brief rest between measurements to evaluate intra-session repeatability. Three additional RNFL circular scans were acquired 1 day later to evaluate intersession repeatability. Two experienced examiners independently measured TRT using automatic alignment and RNFL thickness using manual alignment according to the same procedure to evaluate inter-examiner reproducibility 1 week later. The correlation of measurements by OCT and histology was determined.
Results: For TRT, the intra-session and inter-session intraclass correlation coefficient (ICC) with SD-OCT was between 0.85 and 0.93. The coefficient of variance (CV) ranged from 3.9% to 4.8%. For RNFL thickness, intra-session, and inter-session ICC with SD-OCT were between 0.61 and 0.91. The inter-examiner ICC was 0.74 for TRT and 0.70 for RNFL. The CV was 4.4% for TRT and 6.0% for RNFL. OCT and histologically determined TRT and RNFL thicknesses were significantly positively related based on Pearson's correlation coefficient (TRT, r = 0.781, p < 0.001; RNFL, r = 0.517, p = 0.019).
Conclusions: TRT and RNFL thickness measurements using SD-OCT in rats had high intra-session and inter-session repeatability and inter-examiner reproducibility in vivo. This method will facilitate longitudinal studies to follow disease processes over time and to evaluate therapeutic effects after experimental intervention.
Keywords: RNFL; Rats; SD-OCT; TRT; repeatability; reproducibility.