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Hongli Yang, Stuart K. Gardiner, Galen Williams, Christy Hardin, Nicholas G. Strouthidis, J Crawford C. Downs, Brad Fortune, Claude F. Burgoyne; Spectral Domain Optical Coherence Tomography (SDOCT) Detected Optic Nerve Head (ONH) Change Demonstrates Age-Related Differences in Young vs Old Monkey Early Experimental Glaucoma (EEG). Invest. Ophthalmol. Vis. Sci. 2011;52(14):5921.
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To test the hypothesis that ONH laminar and prelaminar structural change is greater in young versus old monkey EEG eyes at similar levels of cumulative IOP insult and at the onset of Confocal Scanning Laser Tomographic (CSLT) surface change.
SDOCT and CSLT (Spectralis and HRT, Heidelberg Engineering) imaging was performed in 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 unilateral chronic IOP elevation and continued until the onset of EEG as determined by CSLT Topographic Change Analysis (TCA) (requiring 2 confirmations). Masked operators delineated retinal and ONH landmarks in 40 radial B-scans from each eye and time point to quantify change from baseline in the following parameters: Neural Canal Opening (NCO) depth relative to peripheral Bruch’s Membrane (BM), Anterior Lamina Cribrosa Surface depth (ALCSD) relative to the NCO, prelaminar tissue thickness, rim width, cup volume and retinal nerve fiber layer thickness(1200 µm eccentricity). A generalized estimating equation multivariate linear regression model was used to predict the change from baseline for each parameter with predictive factors including age (young vs old), cumulative IOP insult (cumIOP, inter-eye IOP difference × days), and the interaction between those two terms. A second analysis predicted the change from baseline at the time of TCA onset.
On average, cumIOP insult is 54% higher in the older monkeys at the time of sacrifice. As cumIOP insult increased, the anterior laminar surface was significantly posteriorly displaced relative to NCO, NCO was significantly posteriorly displaced relative to peripheral BM and rim width was significantly reduced (P<0.001 in each case). For a given cumIOP insult, ALCSD and NCO displacements as well as the increase in cup volume were significantly lower (p<0.001) in older eyes. At TCA onset, ALCSD displacement was significantly smaller in the old compared to the young eyes.
Our study suggests that on average, in old compared to young eyes, ONH surface change is not detected by CSLT until a greater cumIOP insult has occurred and that there is less ONH laminar and prelaminar deformation for a given level of cumIOP.
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