McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Province of Quebec, Canada.
McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Province of Quebec, Canada School of Optometry, University of Waterloo, Ontario, Canada.
Invest Ophthalmol Vis Sci. 2014 Apr 17;55(7):4098-104. doi: 10.1167/iovs.14-13969.
To better understand the relationship between dichoptic masking in normal vision and suppression in amblyopia we address three questions: First, what is the time course of dichoptic masking in normals and amblyopes? Second, is interocular suppression low-pass or band-pass in its spatial dependence? And third, in the above two regards, is dichoptic masking in normals different from amblyopic suppression?
We measured the dependence of dichoptic masking in normal controls and amblyopes on the temporal duration of presentation under three conditions; monocular (the nontested eye-i.e., dominant eye of normals or nonamblyopic eye of amblyopes, being patched), dichoptic-luminance (the nontested eye seeing a mean luminance-i.e., a DC component) and dichoptic-contrast (the nontested eye seeing high-contrast visual noise). The subject had to detect a letter in the other eye, the contrast of which was varied.
We found that threshold elevation relative to the patched condition occurred in both normals and amblyopes when the nontested eye saw either 1/f or band-pass filtered noise, but not just mean luminance (i.e., there was no masking from the DC component that corresponds to a channel responsive to a spatial frequency of 0 cyc/deg); longer presentation of the target (corresponding to lower temporal frequencies) produced greater threshold elevation.
Dichoptic masking exhibits similar properties in both subject groups, being low-pass temporally and band-pass spatially, so that masking was greatest at the longest presentation durations and was not greatly affected by mean luminance in the nontested eye.
为了更好地理解正常视觉中的双眼竞争掩蔽与弱视中的抑制之间的关系，我们提出了三个问题：首先，正常人和弱视者的双眼竞争掩蔽的时间进程是怎样的？其次，双眼竞争掩蔽的空间依赖关系是低通还是带通？第三，在上述两个方面，正常的双眼竞争掩蔽与弱视的抑制是否不同？
我们在三种条件下测量了正常对照者和弱视者的双眼竞争掩蔽对呈现时间的依赖性；单眼（未测试眼——即正常者的优势眼或弱视者的非弱视眼被遮盖）、双眼亮度（未测试眼看到平均亮度——即 DC 成分）和双眼对比度（未测试眼看到高对比度的视觉噪声）。在另一只眼睛中，我们必须检测一个字母，其对比度是变化的。
我们发现，当未测试眼看到 1/f 或带通滤波噪声时，无论是正常者还是弱视者，相对于遮盖条件，阈值都会升高，但当未测试眼看到平均亮度（即没有来自对应于对空间频率为 0 周/度的通道有反应的 DC 成分的掩蔽）时，阈值不会升高；目标的呈现时间延长（对应于更低的时间频率）会导致阈值升高更大。
双眼竞争掩蔽在两组受试者中表现出相似的特性，即时间上的低通和空间上的带通，因此在最长的呈现时间内掩蔽最大，并且不受未测试眼的平均亮度的影响。
