Sharma V, Levi D M, Coletta N J
College of Optometry, University of Houston, TX 77204-6052, USA.
Vision Res. 1999 Oct;39(21):3526-36. doi: 10.1016/s0042-6989(99)00028-0.
Strabismic amblyopes show losses in positional acuity that cannot be explained by their resolution or contrast sensitivities. One hypothesis for these losses is a reduction in the density of cortical neurons that are driven by the amblyopic eye (cortical undersampling). The question this study addressed was whether the foveal representation of the amblyopic eye is undersampled in the cortex of strabismic amblyopes. In order to assess spatial sampling psychophysically, we recorded the perceived orientation of a stationary grating as a function of grating orientation and frequency in three strabismic amblyopes. To ensure high retinal contrast, the grating was imaged on the fovea of each observer using a laser interferometer. We found that the strabismic amblyopes misperceived the orientation of the grating at spatial frequencies that are a factor of two to six lower than the sampling frequency of the foveal cones. Since the retina and LGN in strabismic amblyopes are presumably normal, this result suggests sparse cortical sampling in the foveal representation of the amblyopic eye. Undersampling by cortical neurons may contribute to the spatial distortions present in strabismic amblyopic eyes.
斜视性弱视患者在位置敏锐度方面存在损失，而这些损失无法通过其分辨力或对比敏感度来解释。对于这些损失的一种假设是，由弱视眼驱动的皮质神经元密度降低（皮质欠采样）。本研究探讨的问题是，在斜视性弱视患者的皮质中，弱视眼的中央凹表征是否存在欠采样。为了从心理物理学角度评估空间采样，我们记录了三名斜视性弱视患者中固定光栅的感知方向，该方向是光栅方向和频率的函数。为确保高视网膜对比度，使用激光干涉仪将光栅成像于每位观察者的中央凹上。我们发现，斜视性弱视患者在比中央凹视锥细胞采样频率低两到六倍的空间频率下会错误感知光栅的方向。由于斜视性弱视患者的视网膜和外侧膝状体可能是正常的，这一结果表明在弱视眼的中央凹表征中存在稀疏的皮质采样。皮质神经元的欠采样可能导致斜视性弱视眼中出现的空间扭曲。
