Ohlendorf Arne, Tabernero Juan, Schaeffel Frank
Institute for Ophthalmic Research, Section of Neurobiology of the Eye, Calwerstrasse 7/1, 72076 Tübingen, Germany.
Vision Res. 2011 Mar 25;51(6):529-34. doi: 10.1016/j.visres.2011.01.010. Epub 2011 Feb 2.
It is well established that spatial adaptation can improve visual acuity over time in the presence of spherical defocus. It is less well known how far adaptation to astigmatic defocus can enhance visual acuity. We adapted subjects to "simulated" and optically-induced "real" astigmatic defocus, and studied how much they adapt and how selective adaptation was for the axis of astigmatism.
Ten subjects with a mean age of 26.7±2.4years (range 23-30) were enrolled in the study, three of them myopic (average spherical equivalent (SE)±SD: -3.08±1.42D) and seven emmetropic (average SE±SD: -0.11±0.18D). All had a corrected minimum visual acuity (VA) of logVA 0.0. For adaptation, subjects watched a movie at 4m distance for 10min that was convolved frame-by-frame with an astigmatic point spread function, equivalent to +3D defocus, or they watched an unfiltered movie but with spectacle frames with a 0/+3D astigmatic trial lenses. Subsequently, visual acuity was determined at the same distance, using high contrast letter acuity charts. Four experiments were performed. In experiment (1), simulated astigmatic defocus was presented both for adaptation and testing, in experiment (2) optically-induced astigmatic defocus was presented both for adaptation and testing of visual acuity. In all these cases, the +3D power meridian was at 0°. In experiments (3) and (4), the +3D power meridian was at 0° during adaptation but rotated to 90° during testing. Astigmatic defocus was simulated in experiment (3) but optically-induced in experiment (4).
Experiments 1 and 2: adaptation to either simulated or real astigmatic defocus increased visual acuity in both test paradigms, simulated (change in VA 0.086±0.069 log units; p<0.01) and lens-induced astigmatic defocus (change in VA 0.068±0.031 log units; p<0.001). Experiments 3 and 4: when the axis was rotated, the improvement in visual acuity failed to reach significance, both for simulated (change in VA 0.042±0.079 log units; p=0.13) and lens-induced astigmatic defocus (change in VA 0.038±0.086 log units; p=0.19).
Adaptation to astigmatic defocus occurs for both simulated and real defocus, and the effects of adaptation seem to be selective for the axis of astigmatism. These observations suggest that adaptation involves a re-adjustment of the spatial filters selectively for astigmatic meridians, although the underlying mechanism must be more complicated than just changes in shapes of the receptive fields of retinal or cortical neurons.
众所周知，在存在球面像散的情况下，空间适应可随时间提高视力。但对于散光性像散的适应能在多大程度上提高视力，人们了解较少。我们使受试者适应“模拟”和光学诱导的“真实”散光性像散，并研究他们的适应程度以及对散光轴的选择性适应情况。
招募了10名平均年龄为26.7±2.4岁（范围23 - 30岁）的受试者，其中3名近视（平均球镜当量（SE）±标准差：-3.08±1.42D），7名正视（平均SE±标准差：-0.11±0.18D）。所有受试者矫正后的最小视力（VA）为logVA 0.0。为进行适应，受试者在4米距离观看一部电影10分钟，该电影逐帧与散光点扩散函数卷积，相当于+3D像散，或者他们观看未经过滤的电影，但佩戴带有0/+3D散光试验镜片的眼镜框。随后，使用高对比度字母视力表在相同距离测定视力。进行了四项实验。在实验（1）中，适应和测试均呈现模拟散光性像散，在实验（2）中，适应和视力测试均呈现光学诱导的散光性像散。在所有这些情况下，+3D屈光力子午线位于0°。在实验（3）和（4）中，适应期间+3D屈光力子午线位于0°，但测试期间旋转至90°。实验（3）中模拟散光性像散，实验（4）中光学诱导散光性像散。
实验1和2：在模拟（视力变化0.086±0.069对数单位；p<0.01）和镜片诱导的散光性像散（视力变化0.068±0.031对数单位；p<0.001）这两种测试范式中，对模拟或真实散光性像散的适应均提高了视力。实验3和4：当轴旋转时，无论是模拟（视力变化0.042±0.079对数单位；p = 0.13）还是镜片诱导的散光性像散（视力变化0.038±0.086对数单位；p = 0.19），视力的改善均未达到显著水平。
无论是模拟像散还是真实像散，对散光性像散的适应都会发生，并且适应效果似乎对散光轴具有选择性。这些观察结果表明，适应涉及对散光子午线的空间滤波器进行选择性重新调整，尽管其潜在机制必定比视网膜或皮质神经元感受野形状的简单变化更为复杂。
