Purpose:
To characterize optic nerve head (ONH) structure within spectral domain optical coherence tomography (SDOCT) images from patients with ocular hypertension and early glaucoma and assess the effect of age on laminar depth while controlling for visual field (VF) loss and retinal nerve fiber layer thickness (RNFLT).
Methods:
This cross-sectional study included 144 participants who underwent 870 nm SDOCT (Heidelberg Spectralis) imaging to obtain 48 high-resolution radial B-scans centered on the ONH, and a standardized ophthalmologic examination including automated perimetry (Humphrey 24-2, SITA Standard). Every second radial scan (24 total) from one randomly selected eye of each patient were delineated and quantified. A random effects model was constructed to assess the relative effects of age, age-corrected VF sensitivity loss (Mean Deviation, MD) and RNFLT (1700 μm eccentricity from the Bruch’s membrane opening (BMO) centroid) on the anterior lamina cribrosa surface depth (ALCSD) relative to BMO reference plane.
Results:
Participants ranged in age from 46 to 90 (mean ± SD: 66 ±10 years). There was no univariate relation between age and ALCSD (p=0.626) or RNFLT (p=0.210). However, the relation between ALCSD and MD was age-dependent. ALCSD = 405.37 - 83.75×MD - 0.09×Age + 1.07×MD×Age (MD p=0.002, Age p=0.927, MD×Age p=0.006). Using RNFLT as a surrogate for "disease stage" instead of MD, ALCSD = 1184.16 - 8.20×RNFLT - 10.45×Age + 0.11×RNFLT×Age (RNFLT p=0.063, Age p=0.080, RNFLT×Age p=0.092). Although no predictors in this second model reached statistical significance at the p<5% level, the same trend was observed as for MD. ALCSD increased with greater damage in younger eyes but not in older eyes. Thus, in older patients, the lamina was shallower than in younger patients with the same level of functional loss or RNFLT defect.
Conclusions:
Our data are consistent with the concepts that old eyes are structurally stiffer than young eyes, and that when structural change is detected in old compared to young eyes they will have a thinner RNFL and greater loss of VF which may be a better surrogate for disease stage in the elderly.
Keywords: aging • lamina cribrosa • imaging/image analysis: clinical