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Galen Williams, Hongli Yang, Brad Fortune, Christy Hardin, Nicholas G. Strouthidis, Stuart K. Gardiner, Claude F. Burgoyne; Change Detection within Optic Nerve Head (ONH) and Retinal Nerve Fiber Layer (RNFL) Parameters Derived by Spectral Domain Optical Coherence Tomography (SDOCT) in Young versus Old Unilateral Experimental Glaucoma (EG) Monkeys. Invest. Ophthalmol. Vis. Sci. 2011;52(14):165.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the onset of change in SDOCT ONH Connective Tissue, Prelaminar and RNFL parameters from both eyes of 4 young and 4 old unilateral EG monkeys prior to the onset of Confocal Scanning Laser Tomographic (CSLT) ONH surface change.
SDOCT and CSLT (Spectralis and HRT, Heidelberg Engineering) were performed on both eyes of 4 young (1.5 to 2.6 yrs) and 4 old (18.6 to 21.9 yrs) monkeys 30 minutes after IOP was manometrically lowered to 10 mm Hg. Imaging was done every 1-2 weeks before and after induction of chronic IOP elevation by trabecular laser treatment, continuing until the onset of CSLT-determined EG occurred. Masked operators delineated retinal and ONH landmarks in 40 radial B-scans (15º diameter) from each eye at each time point to quantify: Anterior Lamina Cribrosa Surface depth (ALCSD) relative to the neural canal opening (NCO), NCO depth relative to peripheral Bruch’s membrane, prelaminar tissue thickness, rim width, cup volume, and RNFL thickness at 1200 µm eccentricity for each eye. Individual parameter "onset" was defined as a change from baseline average exceeding 95% of the baseline variability (CI), confirmed twice. The number of onsets were compared in EG eyes (sensitivity) and control eyes (specificity) using individual eye (IE) versus sample-based (SB) methods of characterizing variability.
Within these 8 EG eyes, the IE CIs generated 25 onsets and the SB CIs generated 16 onsets for the 6 SDOCT ONH parameters. Within the 8 control eyes, IE CIs generated 4 onsets and SB CIs generated 3 onsets. The two most sensitive parameters were ALCSD-NCO, and rim width for both CI methods. In both CI methods, more onsets were detected in young EG eyes than old EG eyes (IE: 14 vs 11; SB: 12 vs 4). Adding a requirement of 2 parameter classes to define onset resulted in 0/8 control eye onsets (both SB and IE CIs) and EG eye onset in 8/8 (IE) and 4/8 (SB) animals.
Within these 8 animals, IE based CIs were more sensitive and less specific than SB CIs when SDOCT parameters were considered individually and in combination. However, the performance of our SB CI approach should improve as we study more eyes. Our data suggest age-related differences in the nature of SDOCT parameter change at the onset of CLST detected surface change in monkey EG.
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