Purpose:
To compare acute SDOCT 10/30 ONH parameter change (SDOCT compliance) within the young and old eyes of NHPs.
Methods:
In one normal eye of 4 young (2.4-3.5 y.o.) and 5 old monkeys (16.1- 24.5 y.o.) SDOCT (Spectralis 870 or 1050nm, Heidelberg Engineering) ONH imaging was performed 30 minutes after manometric IOP lowering to 10 mm Hg and again 30 minutes after increasing IOP to 30 mm Hg within the 40 radial B-scans of the 30º SD-OCT volumes. Masked operators delineated the retinal and ONH landmarks necessary to quantify: anterior lamina cribrosa surface depth (ALCSD) relative to a Bruch’s Membrane Opening (BMO) reference plane (ALCSD-BMO - see figure 1), ALCSD relative to a peripheral BM reference plane (ALCSD-BM), neuroretinal rim width, BMO depth relative to the same peripheral BM reference plane (BMODepth) and anterior scleral opening radius. Random effects models assessed the relative effects of acute IOP elevation, age and their interaction on each parameter.
Results:
In these 9 animals, ALCSD-BMO change due to IOP was significantly greater in young eyes (32 ±12 μm posterior) compared to old eyes (7 ± 12 μm anterior) (p=0.0018). We also found ALCSD-BM change due to IOP in young eyes (68 ± 25 μm posterior) to be significantly larger (p=0.0134) than old eyes (21 ± 18 μm posterior). No significant age effects were observed for BMOdepth, rim width and ASCO radius.
Conclusions:
These are the first in vivo data to suggest that the ONH connective tissues of old NHP eyes are structurally stiffer than those of young NHP eyes. If true in humans, age-related stiffening of the ONH connective tissues may underlie the shallow, senile sclerotic form of glaucomatous cupping.
Keywords: aging • lamina cribrosa • imaging/image analysis: non-clinical