Effects of deep optic nerve head structures on Bruch's membrane opening- minimum rim width and peripapillary retinal nerve fiber layer

Purpose To explore the effects of deep optic nerve head (ONH) structures on Bruch's membrane opening (BMO)-minimum rim width (MRW) and peripapillary retinal nerve fiber layer thickness (pRNFLT) in healthy eyes. Design Prospective cross-sectional study Methods Two hundred five healthy eyes of 141 subjects (mean ± standard deviation of age and axial length (AXL): 46.9±10.0 years and 24.79±1.15 mm) were enrolled. Best fit multivariable linear mixed models identified factors associated with BMO-MRW and pRNFLT. Explanatory variables included age, sex, AXL, BMO and anterior scleral canal opening (ASCO) area and ovality, magnitude of BMO and ASCO shift, peripapillary choroidal thickness, lamina cribrosa (LC) parameters, prelaminar thickness and peripapillary scleral (PPS) angle. Results Thinner BMO-MRW was associated with older age, smaller ASCO/BMO offset magnitude, larger BMO area, thinner prelaminar thickness, deeper LC, and thinner pRNFLT (p=0.011, <0.001, 0.004, <0.001, <0.001, <0.001 respectively). Thinner pRNFLT was associated with shorter AXL, smaller ASCO area, a more posteriorly bowed PPS, shallower LC and thinner BMO-MRW. (p=0.030, 0.002, 0.035, 0.012, <0.001 respectively) Conclusions BMO-MRW and pRNFLT were influenced by several deep ONH structures such as BMO and ASCO position shift, BMO or ASCO area, prelaminar thickness, PPS bowing and LC depth in addition to patient characteristics such as age and AXL. The degree and/or direction of associations varied between deep ONH structures and BMO-MRW or pRNFLT. Despite both BMO-MRW and pRNFLT being surrogate parameters for RGC loss, a complex relationship with ONH deep-layer morphology was indicated.