Repeatability and Reproducibility of Retinal Neuronal and Axonal Measures on Spectral-Domain Optical Coherence Tomography in Patients with Cognitive Impairment

Edwin Hong-Teck Loh, Yi-Ting Ong, Narayanaswamy Venketasubramanian, Saima Hilal, Naing Thet, Tien Yin Wong, Christopher P. L. Chen, Carol Yim-lui Cheung

With increasing interest in determining if measurement of retinal neuronal structure with spectral-domain optical coherence tomography (SD-OCT) is useful in accessing neurodegenerative process in cognitive decline and development of dementia, it is important to evaluate whether the SD-OCT measurements are repeatable and reproducible in these patients. This is a retrospective cohort study. Patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI) with no change in global clinical dementia rating (CDR) score at 1-year follow-up were eligible to be included. Ganglion cell-inner plexiform layer (GC-IPL) and retinal nerve fiber layer (RNFL) parameters were measured with SD-OCT at baseline, 6-month, and 1-year follow-up visits. At baseline, SD-OCT scans were repeated to access intra-visit repeatability of the SD-OCT measurement. SD-OCT measurement over three visits was used to access inter-visit reproducibility. We calculated intraclass correlation coefficients (ICC) and coefficients of variation (CoVs). We included 32 patients with stable AD and 29 patients with stable MCI in the final analysis. For GC-IPL measures, the average intra-visit ICC was 0.969 (range: 0.948-0.985), and CoV was 1.81% (range: 1.14-2.40); while the average inter-visit ICC was 0.968 (0.941-0.985), and CoV was 1.91% (range: 1.24-2.32). The average ICC and CoV of intra-visit RNFL measured were 0.965 (range: 0.937-0.986) and 2.32% (range: 1.34-2.90%), respectively. The average ICC and CoV of inter-visit RNFL measures were 0.927 (range: 0.845-0.961) and 3.83% (range: 2.71-5.25%), respectively. Both GC-IPL and RNFL measurements had good intra-visit repeatability and inter-visit reproducibility over 1 year in elderly patients with no decline in cognitive function, suggesting that SD-OCT is a reliable tool to assess neurodegenerative process over time.