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When the single 2D image is viewed with proper eye convergence, it causes the brain to fuse different patterns perceived by the two eyes into a virtual 3D image without, hidden within the 2D image, the aid of any optical equipment. SIS images are created using a repeating pattern. [18] [29] Programs for their creation include Mathematica. [30] [31]
Figure 1. Definition of binocular disparity (far and near). Human eyes are horizontally separated by about 50–75 mm (interpupillary distance) depending on each individual. Thus, each eye has a slightly different view of the world around. This can be easily seen when alternately closing one eye while looking at a vertical edge.
Incorrect vergence response can cause double vision. Accommodation is the eye’s focusing mechanism and it is engaged to produce a sharp image on a retina. Both of these mechanisms are neurally linked forming the accommodation-convergence reflex [1] of eyes.
The convergence will stretch the extraocular muscles – the receptors for this are muscle spindles. As happens with the monocular accommodation cue, kinesthetic sensations from these extraocular muscles also help in distance and depth perception. The angle of convergence is smaller when the eye is fixating on objects which are far away.
Stereoblindness (also stereo blindness) is the inability to see in 3D using stereopsis, or stereo vision, resulting in an inability to perceive stereoscopic depth by combining and comparing images from the two eyes. Individuals with only one functioning eye have this condition by definition since the visual input of the second eye does not exist.
Stereoscopy creates the impression of three-dimensional depth from a pair of two-dimensional images. [5] Human vision, including the perception of depth, is a complex process, which only begins with the acquisition of visual information taken in through the eyes; much processing ensues within the brain, as it strives to make sense of the raw information.
The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others.
The visual system performs a number of complex tasks based on the image forming functionality of the eye, including the formation of monocular images, the neural mechanisms underlying stereopsis and assessment of distances to (depth perception) and between objects, motion perception, pattern recognition, accurate motor coordination under visual ...