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D.Y. Lee, A.J. Zele, J. Pokorny, D. Ireland; Anisometropic Amblyopia: Spatial Contrast Sensitivity Deficits in Inferred Parvocellular and Magnocellular Vision . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5361.
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We measured achromatic spatial contrast sensitivity in patients with anisometropic amblyopia under conditions favoring inferred parvocellular (PC) or magnocellular (MC) pathway mediation.
Ten anisometropic amblyopes (VA amblyopic eye < or =6/12; better eye >6/7.5) and 9 age–matched normal controls participated (VA 6/6; 15.3 yrs, range: 8 – 31 yrs). Foveal spatial contrast sensitivity was measured using localized, spatially narrow band targets (0.25–8.0 c/deg) presented in the center of a steady–pedestal (favoring MC detection) or pulsed–pedestal (favoring PC detection) that was set within a uniform 115 Td surround (Leonova et al, 2003 Vision Research, 43, 2133).
The spatial contrast sensitivity function was bandpass for the steady–pedestal and lowpass for the pulsed–pedestal, consistent with published data. Under steady–pedestal adaptation, the amblyopes showed reduced spatial contrast sensitivity at intermediate frequencies (1–2 c/deg), consistent with MC sensitivity loss. For the pulsed–pedestal, there was a generalized loss across all spatial frequencies (0.5–4 c/deg), consistent with PC sensitivity loss. The magnitude of the amblyopic spatial contrast sensitivity loss for the steady–pedestal paradigm was greater than that for the pulsed–pedestal paradigm (0.5–2 c/deg). In the pulsed–pedestal paradigm, results for the better eye of 7 of 9 amblyopes were within the 95% confidence interval of the normal control observers, and for all better eyes in the steady–pedestal paradigm.
Anisometropic amblyopia produces spatial contrast sensitivity losses in both inferred PC– and MC–mediated vision, with a larger deficit evident for the inferred MC–system. With spatially localized stimuli, we showed performance of the better eye in amblyopes fell within the 95% confidence interval. Our results suggest that previously reported modest reductions in spatial contrast sensitivity might be due to crowding.
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