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ABSTRACT
Purpose: To quantify variation in spectral-domain optical coherence tomography (SD-OCT) measures of total retinal thickness (top of inner limiting membrane to top of retinal pigment epithelium, RPE) and RPE thickness measures over a 4-week period and by age.
Methods: A total of 76 volunteers aged 40–85 years were seen at three visits over 4 weeks. Two Topcon SD-OCT scans were taken at each visit. Following grid re-centration, total retinal and RPE thickness were determined in nine subfields. Multilevel modeling was used to quantify variance between scans and by age.
Results: In the central circle, mean total retinal thickness was 237.9 µm (standard deviation, SD, 23.5 µm) and RPE thickness was 46.0 µm (SD 5.3 µm). Intraclass correlation coefficient in the central circle was 0.988 for total retinal thickness and 0.714 for RPE thickness. Pairwise measures taken within 4 weeks were strongly correlated (p > 0.95). Within-subject variation of total retinal thickness increased significantly with age. Subjects in the oldest age group had significantly increased among- and within-subject variability in measures of RPE thickness.
Conclusions: Correlation between retinal thickness measures was very high (>0.95) over a period of 4 weeks with small changes likely due to variation in measurement. Increasing variability in total retinal and RPE thickness measures with age suggest that the use of more and/or higher quality images to calculate mean thickness to reduce variability may benefit the study of these measures in older persons. This may also impact sample size calculations for future studies of SD-OCT measures in older adults.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.
This study was supported by National Institutes of Health grant EY06594 (BEK Klein and R Klein), National Institutes of Health, Bethesda, MD, USA and, in part, by an unrestricted grant from Research to Prevent Blindness (RPB), New York, NY, USA. The National Eye Institute provided funding for the entire study including collection and analyses of data; RPB provided additional support for the data analyses. The content is solely the responsibility of the authors and does not necessarily reflect the official views of the National Eye Institute or the National Institutes of Health.
Supplementary material
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