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Abstract #49235 Published in IGR 14-1
The Optic Nerve Head As A Robust Biomechanical System
Sigal IA; Bilonick RA; Kagemann L; Wollstein G; Ishikawa H; Schuman JS; Grimm JLInvestigative Ophthalmology and Visual Science 2012; 53: 2658-2667
PURPOSE: Understanding the effects of IOP on the optic nerve head (ONH) is important in understanding glaucoma and ONH structure and function. We tested the hypothesis that the ONH is a robust biomechanical structure wherein various factors combine to produce a relatively stable response to IOP. METHODS: We generated two populations of 100,000 ONH numerical models each with randomly selected values, but controlled distributions, either uniform or Gaussian, of ONH geometry and mechanical properties. We predicted the lamina cribrosa displacement, scleral canal expansion, and the stresses (forces) and deformations (strains) produced by a 10 mmHg increase in IOP. We analyzed the distributions of the responses. RESULTS: The responses were distributed non-uniformly, with the majority of the models having a response within a small region, often less than 30% of the size of the overall response region. This concentration of responses was more marked in the Gaussian population than in the uniform population. All the responses were positively skewed. Whether a particular case was typical or not depended on the response used for classification and on whether the decision was made using one or two-dimensional criteria. CONCLUSIONS: Despite wide variations in ONH characteristics and responses to IOP, some responses were much more common than others. This supports conceiving of the eye as a robust structure, particularly for LCD and SCE, which is tolerant to variations in tissue geometry and mechanical properties. We also provide the first estimates of the typical mechanical response of the ONH to variations in IOP over a large population of ONHs.
Ophthalmology, University of Pittsburgh, 203 Lothrop St, Rm 930, Pittsburgh, PA, USA.
Full articleClassification:
2.14 Optic disc (Part of: 2 Anatomical structures in glaucoma)