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Mark J. Kupersmith, Gary Mandel, Melissa Horne, Mary Durbin, Randy Kardon; Optical Imaging Differentiation of RNFL Changes Due to Optic Nerve Head Swelling. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5309.
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© ARVO (1962-2015); The Authors (2016-present)
OCT shows retinal nerve fiber layer (RNFL) thickening in optic disc edema caused by papilledema, anterior ischemic optic neuropathy (NAION), or optic neuritis, but does not provide information on acute axonal disruption. We hypothesize that differing mechanisms of acute RNFL swelling might be revealed by comparing OCT and SLP findings. Specifically, reduced retardance by SLP may be found in NAION with anticipated early, permanent axonal injury.
We prospectively studied patients with acute optic disc edema due to optic neuritis, NAION, or papilledema, utilizing threshold perimetry, OCT, and SLP. We analyzed eyes only if average RNFL by OCT was swollen (> 95th percentile of controls). RNFL was judged reduced if the thickness or retardance in 1 quadrant was < 5th percentile of controls. We also analyzed results obtained at 1 month in eyes with optic neuritis and NAION.
At presentation, the mean for average RNFL for OCT was 213 µ for 24 eyes (14 patients) with papilledema, 141 µ for 13 optic neuritis eyes and 208 µ for 21 NAION (p=0.9) eyes. The mean for average SLP was 60 µ for papilledema, 56 µ for optic neuritis and 48 µ for NAION (p=0.02) eyes. At presentation, the average SLP was swollen in 1 eye with papilledema and in none with NAION or optic neuritis. SLP retardance was reduced in 1 quadrant in 1/24 eyes with papilledema and in 1/13 eyes with optic neuritis, but in 1 or more quadrants in 12/21 eyes with NAION. No eyes had RNFL thinned by OCT at presentation. Quadrants with reduced retardation had corresponding visual field loss in all 12 NAION eyes and did not recover at 1 month. At 1 month RNFL was reduced by OCT in 7/12 and by SLP in 12/14 eyes with NAION but was not reduced in optic neuritis by OCT (0/11; p=0.006) or SLP (1/11; p=0.0004).
Although OCT is superior to SLP in demonstrating RNFL swelling for all causes. Acutely, SLP retardance reduction seems to show axonal injury associated with visual field loss that does not recover, especially in NAION.
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