Distorted optical input affects human perception

Abstract

collinear facilitation, the mechanism for grouping contour elements, is a process involving lateral interactions that improve the detectability of a target by the presence of collinear flankers. It was shown that the development of collinear facilitation is experience dependent and that it may be impaired when the visual input is distorted in one meridian (meridional amblyopia). In oblique astigmatism, the blurring is on the opposite oblique meridian in both eyes, resulting in two conflicting images, which may affect the development of binocular vision. We hypothesized that the collinear facilitation of adults with oblique astigmatism is reminiscent of the abnormal development of the lateral facilitation of meridional amblyopia. We explored the perception of binocular vision and collinear facilitation in cases of both distorted and non-distorted vision. Fully corrected participants that tested for the target contrast detection of Gabor patches and two collinear flankers, presented for 80 ms, were positioned at different orientations (0° (180°), 45°, 90°, and 135°) and for different eyes (monocular, binocular). The results show a significant anisotropy for monocular collinear facilitation between the blured and the clear meridians, being lower in the blurriest meridian than in the clearest meridian, resembling the meridional amblyopia results. Collinear facilitation results in poor binocular summation between the monocular channels. Our results indicate that the perceptual behavior was similar to that of meridional amblyopic subjects having an anisotropy of collinear facilitation between cardinal meridians in oblique astigmatic subjects. Normal vision, emmetropia, is when parallel light rays, coming from an object located at more than 6 m away, focus on the retina at the focus point. A refractive error occurs when the light does not focus on the retina due to the shape of the eye. The most common type of refractive error is myopia (nearsightedness), resulting in the perception of far objects as blured because the focus point is before the retina. Astigmatism is a refractive error due to a deviation from the spherical curvature of the cornea and a crystalline lens 1 , resulting in a blured image along the distorted meridian. It occurs when rays propagating in perpendicular planes through the eye are focused at different distances 2. Thus, the refractive power is different in various meridians and consequently, there is a meridian with a high refractive error and a perpendicular meridian with a weaker refractive error. The distant object has two focal lines perpendicular to the meridians having the maximum and minimum power; thus, two points of focus are formed. Therefore, there are two different images on the retina. Astigmatism can be classified based on its axis orientation. A recent study of Americans showed a prevalence of astigmatism that is 40% of all refractive errors 3 , and another study in China found that the incidence of astigmatism was five time higher in myopic subjects than in non-myopic ones 4. The ...

Meridional binocular rivalry reveals a trace of uncorrected oblique input during development in the adult brain

“…Thus, the process of adjusting to persistently distorted input during development may have a long-term abnormal effect on neuronal connectivity. In our recent study, we showed that participants with OA have lower collinear facilitation in the blurred meridians of each eye 12 . We suggested that these results are reminiscent of the development of meridional amblyopia and that the monocular anisotropy could be a cortical trace of uncorrected astigmatism during the development period , which is observed in adulthood 12 .…”

“…In our recent study 12 we showed that participants with OA have impaired lateral interactions in the blurred meridians of each eye, which is reminiscent of the impaired lateral interactions in meridional amblyopia 13 . Moreover, previous research suggests that visual experiences during the sensitivity period can affect the development of BR and potentially have long-term effects on visual perception 14 .…”