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Ronald S. Harwerth; Structure/function relationships in glaucoma. Journal of Vision 2009;9(14):15. doi: 10.1167/9.14.15.
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© ARVO (1962-2015); The Authors (2016-present)
The glaucomas are a group of relatively common optic neuropathies, in which the pathological loss of retinal ganglion cells (RGCs) causes progressive reduction of retinal nerve fiber layer (RNFL) thickness with an associated loss of sight. The diagnosis and management of glaucoma often depend on measurements that either, 1) identify and quantify patterns of functional visual defects by standard automated perimetry (SAP), or 2) quantify structural defects in the RNFL by optical coherence tomography (OCT), but the two types of measurements should be correlated. The present studies were undertaken to formalize the psycho-physiological links between loss of visual sensitivity and thinning of the RNFL. The basis for the linking propositions was the pointwise relationship between visual sensitivity and histologic RGC densities in monkeys with experimental glaucoma. The further clinical development was based on data from clinical studies of normal aging and of primary open-angle glaucoma. The final formulation for direct comparisons of SAP and OCT data required two components - one for the nonlinear relationship between visual sensitivity and RGC somas and another for the linear relationship between RNFL thickness and RGC axons. The accuracy and precision for predicting the thickness of peripapillary RNFL from the SAP sensitivities in corresponding regions was evaluated with data for two independent populations of patients with glaucoma. For both groups, the relationship between the predicted and measured RNFL thicknesses were well-described by a unity correlation. Thus, the model for linking structure and function provides information that is important in understanding glaucomatous neuropathy, and which may have clinical application for inter-test comparisons of the stage of disease.
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