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R.H. Kardon, O. Bergamin, S.C. Anderson; The Relationship Between Retinal Nerve Fiber Loss, Relative Afferent Pupil Defect, and Visual Field Loss in Optic Neuropathy . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1959.
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Purpose: Structural damage to the optic nerve resulting in thinning of the retinal nerve fiber layer (RNFL) was compared to functional damage to the visual field and pupil light reflex in patients with different causes of optic neuropathies in order to understand the effect of disease on structural-functional relationships in the eye. Methods:94 patients with optic neuropathy due to compression, ischemia, demyelination (recovered), or glaucoma were assessed functionally by automated perimetry (Humphrey 24-2 SITA) and asymmetry of the pupil light reflex measured using neutral density filters to quantify the log unit relative afferent pupil defect (RAPD). The average RNFL thickness was measured in each eye by optical coherence tomography (OCT). Results: A significant linear correlation (R2) was found between the interocular difference in nerve fiber layer thickness (microns) and the relative afferent pupil defect (RAPD; decibel interocular asymmetry) and mean deviation (MD; decibel interocular asymmetry) of the automated visual field, as shown in the table. In recovered optic neuritis, the amount of functional loss per nerve fiber layer asymmetry was much less than in other optic neuropathies (slope of linear fit was less). The relationship between RNFL thickness and MD for individual damaged eyes was non-linear. Conclusions: Patients with recovered optic neuritis showed better visual function than predicted by the nerve fiber layer thickness, and may be exhibiting a compensatory mechanism in the visual pathway to provide good function in spite of nerve fiber loss. Correlation of structure with function in patients with optic neuropathy gives new information that can help classify disorders of the optic nerve, reveal the extent of reversible damage, and may point to compensatory mechanisms that in some cases help to maintain function in spite of structural loss of nerves. Linear Correlation Between Structure and Function of RNFL View OriginalDownload SlideView OriginalDownload Slide
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