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R. D. Fechtner, A. S. Khouri, M. J. Sinai, P. J. Lama, M. Fingeret; Are Normal Optic Nerves Symmetric?. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2449.
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© ARVO (1962-2015); The Authors (2016-present)
Optic nerve asymmetry has long been considered an indicator of glaucomatous optic neuropathy. Normative scanning laser topographic parameters have been created for individual eyes, but paired comparisons to determine normal symmetry are not available. This study establishes parameters of symmetry for normal pairs of eyes.
A normative database consisting of 281 pairs of eyes was accessed. All subjects were Caucasian and had no ocular pathology that might affect the optic nerve. We calculated the mean differences between eyes (left-right eye), standard deviations, and coefficients of variations (COV) for global and sectoral parameters including: Disc area, cup area and volume, rim area and volume, cup shape measure, and mean retinal nerve fiber layer (RNFL).
Pairs of eyes were, on average, symmetric with low COV. Rim volume and mean RNFL thickness were the two parameters with the highest COV. For each of these the sector contributing the greatest variability was the temporal/inferior. Global results are summarized in the Table.
We have established normative parameters for optic nerve symmetry in healthy eyes. These parameter can be used to develop additional tools for the identification of glaucoma based on loss of symmetry.
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