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R. H. Kardon, R. A. Longmuir, A. G. Lee, S. Anderson; Smaller Optic Disc Area Correlates With Greater Permanent Damage Following Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION). Invest. Ophthalmol. Vis. Sci. 2010;51(13):653.
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The tern "disc at risk" refers to the greater prevalence of small cup size in the fellow eye of patients with NAION. A smaller nerve head compartment in ischemic disc edema may also predispose to greater permanent damage in NAION. To investigate this hypothesis, the optic disc area was correlated with static perimetry and retinal nerve fiber layer thickness (RNFL) measured at least 6 months after the acute event.
18 eyes with NAION > 6 months duration and 75 normal eyes were tested by static automated perimetry (Humphrey 24-2 SITA) and optical coherence tomography (OCT3). The optic disc area was quantified using the OCT fast disc scan. The seed points of each of the radial B scans that designate the disc border where Bruch’s membrane ends were manually placed by the authors. The OCT derived disc area was correlated with the mean deviation (MD) of the visual field and the average RNFL thickness.
Disc area was significantly smaller in eyes with AION compared to normal eyes (p<0.001, Rank Sum Test). In eyes with NAION, a highly significant negative correlation was found between disc area and RNFL thickness (r=.619, p<0.006, Pearson correlation) and between MD and RNFL thickness (r=.628, p<0.005). This correlation could not be accounted for by the association between disc size, MD, and RNFL in normal eyes or in optic nerve hypoplasia (n=28).
Eyes with NAION have a smaller optic disc area, explaining smaller cup size in the disc at risk. A smaller disc area also was associated with more permanent damage resulting from NAION as measured by either degree of perimetric threshold loss or RNFL (axon) loss. Patients with NAION and small disc area have a worse prognosis, which may relate to the adverse effect of a small compartment in ischemic optic disc edema.
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