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A. L. A. Moura, M. Gualtieri, R. A. A. Teixeira, M. L. Bandeira, D. Callegaro, R. D. Hamer, D. F. Ventura; Magno and Parvocellular Pathways Responses in Patients With Multiple Sclerosis. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2897.
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© ARVO (1962-2015); The Authors (2016-present)
To assess magnocellular (M) and parvocellular (P) responses in patients with multiple sclerosis (MS), with and without history of optic neuritis.
We evaluated 21 patients with diagnosis of MS (16F; 5M; mean age = 34.8±10.34 years). All patients had visual acuity between 0 and 0.1 logMAR and had no significant findings in an ophthalmologic exam performed at the time of testing. Nine patients had optic neuritis episodes between 1 and 26 years prior to the test. We used Pokorny & Smith’s (1997) Steady-Pedestal (SP) and Pulsed-Pedestal (PP) paradigms as adapted recently by Gualtieri et al. (2006). For both paradigms, a pedestal of four 10x10 squares was presented on a 12 cd/m2 surround, and observers had to detect a brief (17 or 133 ms) increment of luminance of one of these (the test square, TS). For the PP paradigm, the pedestal was pulsed along with the TS, which was modulated relative to the other 3 squares. For the SP paradigm, the pedestal was on continuously, and only the TS was modulated. Pedestal luminances were 7, 12 and 19 cd/m2. Thresholds were measured using a double-interleaved staircase, in 4-alternative forced-choice task. Prior research indicates that the SP and PP paradigms reflect M- and P-dominated responses, respectively.
For the PP paradigm, patients’ contrast thresholds were significantly elevated at all 3 pedestal levels for the 133 ms TS duration. For the 17 ms TS, their thresholds were elevated for the 12 and 19 cd/m2 pedestals (Mann-Whitney U-test, p < 0.01). For the SP paradigm, patient’s thresholds were significantly elevated for both test durations, but only for the 12 cd/m2 pedestal. There were no significant differences between thresholds from MS patients with and without a previous neuritis episode. Threshold data did not correlate with time of disease.
Consistent with some prior reports (Caruana et al, 2000), the MS patients evaluated in this study had reduced contrast sensitivity mainly in the PP paradigm, suggesting preferential loss in the P pathway.
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