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Christy A. Hardin, Hongli Yang, Galen Williams, Nicholas G. Strouthidis, Stuart Gardiner, Brad Fortune, Claude Burgoyne; Individual-eye (IE) Versus Sample-based (SB) Variability Estimates for Optic Nerve Head (ONH) and Retinal Nerve Fiber Layer (RNFL) Spectral Domain Optical Coherence Tomography (SDOCT) Parameters in Non-Human Primates (NHPs). Invest. Ophthalmol. Vis. Sci. 2011;52(14):174.
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© ARVO (1962-2015); The Authors (2016-present)
To assess IE and SB variability estimates for ONH connective tissue, ONH prelaminar tissue and RNFL structural parameters during normal baseline testing and to test for age related variability differences in animals with early experimental glaucoma (EEG).
ONH imaging was performed in both eyes of 16 NHPs by Spectralis SDOCT and Confocal Scanning Laser Tomography (CSLT, HRT, Heidelberg Engineering) 30 minutes after IOP was manometrically lowered to 10 mm Hg. Four NHPs were young (2 to 3 yrs), 4 were old (18 to 22 yrs) and 8 were ages 9 to 19 yrs. Imaging was done every 1-2 weeks during baseline (BL) and after unilateral laser-induced, chronic IOP elevation until the onset of CSLT-determined EEG. Masked operators delineated retinal and ONH landmarks in 40 radial B-scans (15 deg diameter) from each eye at each session to quantify a series of ONH laminar, prelaminar and RNFL parameters. Using all 32 eyes, pairwise differences between pre-laser SDOCT volumes from the same eye were bootstrapped to calculate a SB 95% confidence interval (CI) for the BL inter-test variability of each parameter. For each eye of the 4 young and 4 old animals, IE 95% CIs of each parameter were calculated using the 3-5 baselines for each eye and were then compared to the width of the SB 95%CIs. A linear regression model was used to predict the magnitude of the IE CI width for each parameter and eye, based on age and (future) treatment status.
In the groups of 4 young and 4 old animals, 113 out of 176 IE CI widths were narrower than the SB CI widths for the 11 SDOCT parameters. The linear regression analysis revealed that none of the parameters exhibited significant differences in the IE CI widths between control and treated eyes, however, Anterior Lamina Cribrosa Surface Depth, Prelaminar Tissue Thickness and Cup Volume each had significant age effects such that old eye IE CI widths were significantly (P<0.05) narrower than young eye IE CI widths. No significant differences were found in CI widths for RNFL parameters.
Our results suggest that normal variability in SDOCT ONH parameters may demonstrate age-related effects in young and old NHP eyes. Old eyes tend to be less variable than young eyes for ONH connective tissue and ONH prelaminar parameters but equally variable for RNFL parameters.
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