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V. R. Patel, T. W. Winter, J. H. Gil-Flamer, D. T. Huang, A. A. Sadun; Kinetics of Retinal Nerve Fiber Layer Thickness Change as a Function of Stage of Resolution of Optic Neuritis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):918.
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To determine the rate of change in Retinal Nerve Fiber Layer (RNFL) thickness in optic neuritis patients at various stages of resolution.
We conducted a prospective, comparative study on 28 eyes of 25 patients with demyelinating optic neuritis. Circumpapillary RNFL thickness measurements were obtained for each patient using the Zeiss Strata OCT 3 imaging device. We divided our study population into 2 groups. Group 1 (n=15) included those who received their first OCT scan within 20 weeks of their optic neuritis event (mean = 4.6 weeks, acute group), and group 2 (n=10) included all patients whose first OCT scan was performed greater than 20 weeks (mean = 46 weeks) from onset of optic neuritis (chronic group). Each initial OCT scan was followed by a second scan (mean interval between OCTs = 8.6 weeks, range = 6 to 32 weeks). Absolute change in RNFL thickness over time was recorded for each patient. RNFL thickness measurements were plotted as a function of time. The rate of change in RNFL thickness was graphically inferred by calculating the slope of the best-fit line connecting the two RNFL measurements for each patient.
The acute group demonstrated an average absolute reduction in RNFL thickness of 73.9 microns (SD +/-10.6 microns), whereas the chronic group revealed an average increase in RNFL thickness of 4.2 microns (SD+/ -0.20 microns). The rate of change in RNFL thickness was 57.2 times greater for the acute group compared to the chronic group (-9.85 vs. 0.17, respectively).
RNFL thickness changes precipitously in the acute phase of optic neuritis relative to that seen in the chronic phase. The sharp decline in RNFL thickness over time observed in acute cases in part represents resolution of edema in addition to nerve fiber atrophy. Optic nerves in the chronic phase tended to demonstrate stability in RNFL thickness. The trend toward a slight but consistent increase in RNFL thickness in the chronic group may be due to gliotic changes overlying the ganglion cell axons. High resolution OCT imaging may allow differentiation of gliosis from the remaining axons.
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