A common framework for ambylopic, developmental and adult forms of visual crowding

在我们的视野中，当我们直视物体时，物体通常很容易看到，而在外围（我们视觉的“边缘”）则很难看到。这种差异不仅仅与分辨率有关-即使外围的目标物体足够大，可以单独看到，其附近的其他物体的放置也会使目标变得“混乱”，无法识别。这就是所谓的“视觉拥挤”。是拥挤而不是简单的分辨率限制了我们对超过95%的视野的物体识别。虽然拥挤不会影响“正常”视力的注视中心，但斜视性弱视的情况下，它会变得更高，通常被称为“懒惰的眼睛”。弱视是儿童视力损害的最常见原因，影响约3%的人口。其定义为尽管进行了光学矫正，但一只眼睛的分辨率受损。此外，弱视眼也受到拥挤的强烈影响-即使物体足够大，可以单独看到，在混乱的环境中，注视中心的视力也会受到严重损害。最近的研究表明，12岁以下儿童的中心视力同样受到拥挤的影响。也就是说，成年人可以在直接注视时识别出近距离的物体，但儿童则不然。这严重限制了儿童的视力和学习阅读的能力。然而，我们对此知之甚少。我们在这里有三个视觉拥挤的例子：正常的周边视觉，弱视眼和幼儿的眼睛。我们不知道的是，这三种形式的拥挤是否有一个共同的根本原因。我们能否以同样的方式，使用同样的理论来考虑每一个问题，从而应用同样的治疗方法和应对策略来克服拥挤？我们的假设是，所有形式的拥挤都代表了一种“强制整合”的形式，当大脑面临有限的资源时，就会发生这种情况：当我们大脑中处理视觉的细胞数量不足时，它们会在扩展的区域中聚集以进行补偿。该项目的目的是比较这三种形式的拥挤，并确定它们是否符合这一共同框架。该研究将由心理学家，神经科学家，骨科医生和眼科医生进行，有四个具体目标。首先，我们将确定拥挤如何影响对象的外观。也就是说，在儿童的中心视觉中，杂乱的场景看起来和在边缘视觉中的成人一样吗？这是测试强制整合理论预测的核心，并将导致在这些情况下模拟视觉的计算机模型的发展。其次，我们将检查正常视力的周边视野是否与弱视患者的中心视力相似-眼睛之间是否存在差异，我们能否以治疗弱视的方式减少差异？这就为“正常”的周边区域成为新的弱视治疗方法的试验场创造了可能性，而不需要冒儿童中央视力的风险。第三，我们将研究拥挤是视觉中的一个单一过程，还是一种单独影响不同对象的综合形式。例如，拥挤是否会像影响字母一样影响移动的物体？这不仅将在每一种拥挤情况下检验强制性融合假设，而且有可能开发新的、更敏感的拥挤检验方法。最后，我们将扫描“正常”和弱视成年人的大脑，以测量在整个视野中发生的拥挤变化是否遵循这些视野相同部分的神经资源的变化。这将允许在正常和弱视视觉中直接检验强制整合假说。

In our visual field, objects are typically easy to see when we look directly at them and difficult to see in the periphery (the 'edges' of our vision). This difference is not simply to do with resolution - even when a target object in the periphery is large enough to be seen in isolation, the placement of other objects in its immediate vicinity can render the target 'jumbled' and impossible to recognise. This is known as 'visual crowding'. It is crowding and not simple resolution that limits our object recognition over more than 95% of the visual field.Although crowding does not affect the centre of gaze in 'normal' vision, it becomes elevated the case of strabismic amblyopia, often known as 'lazy eye'. Amblyopia is the most common cause of visual impairment in children and affects ~3% of the population. It is defined by impaired resolution in one eye that occurs despite optical correction. In addition, the amblyopic eye is also strongly affected by crowding - even when objects are large enough to be seen in isolation, vision at the centre of gaze is highly impaired in cluttered environments. Recent research suggests that the central vision of children younger than 12 is similarly affected by crowding. That is, where adults can recognise closely spaced objects when gazing directly at them, the same is not true for children. This places a significant restriction on the vision of children and processes such as their ability to learn to read. However, we know very little about it.We have here three instances of visual crowding: in normal peripheral vision, in amblyopic eyes and in the eyes of young children. What we do not know is whether these three forms of crowding have a common underlying cause. Can we consider each in the same way, using the same theory, and thus apply the same treatments and coping strategies to overcome crowding? Our hypothesis is that crowding in all its forms represents a form of 'compulsory integration' that occurs when the brain is faced with limited resources: when the cells in our brain that process vision are insufficient in number, they pool across extended regions to compensate. The aim of this project is to compare these three forms of crowding and determine whether they fit this common framework.The research will be conducted by psychologists, neuroscientists, orthoptists and ophthalmologists, with four specific goals. First, we will determine how crowding affects the appearance of objects. That is, do cluttered scenes look the same to children in their central vision as they do to adults in the periphery? This is central to testing the predictions of the compulsory integration theory and will lead to the development of computer models that simulate vision in these circumstances. Second, we will examine whether the peripheral field in normal vision is like the central vision of those with amblyopia - are there differences between the eyes and can we reduce them in the same way that we treat amblyopia? This creates the possibility for the 'normal' periphery to become a testing ground for new treatments of amblyopia, without the need to risk the central vision of children. Third, we will examine whether crowding is a single process in vision, or a general form of integration that affects different objects separately. For instance, does crowding affect moving objects in the same way that it affects letters? This will not only test the compulsory integration hypothesis in each instance of crowding, but also has the potential to develop new, more sensitive tests for crowding. Finally, we will scan the brains of 'normal' and amblyopic adults to measure whether the variation in crowding that occurs across the visual field follows the variation in neural resources to these same parts of the visual field. This will allow a direct test of the compulsory integration hypothesis in normal and amblyopic vision.