Final answer:
The majority of strabismics have anomalous HARC and foveal suppression, which are adaptations to maintain single vision despite eye misalignment. Anomalous HARC involves non-identical retinal correspondence between the eyes, and foveal suppression prevents double vision by ignoring the image from the deviating eye's fovea.
Step-by-step explanation:
The majority of strabismics have anomalous HARC (Heteronymous Anomalous Retinal Correspondence) and foveal suppression. When discussing strabismus, which is a misalignment of the eyes, anomalous retinal correspondence and suppression are common adaptive mechanisms that the visual system may develop. Anomalous HARC is an adaptation in which the corresponding retinal areas in each eye have a different spatial orientation than normal. This leads to each eye sending the brain images from non-identical areas of the retina, which can decrease double vision but disrupt binocular vision. Foveal suppression refers to the brain ignoring the visual input from the fovea (the central part of the retina) of the deviating eye, thus avoiding confusion and double vision from disparate images sent to the brain from the two eyes.
Astigmatism is another vision defect commonly discussed in context with eye function. Astigmatism is caused by the asymmetrical focusing of light due to irregularities in the cornea or lens. Objects appear blurred or elongated due to this uneven focus. On the other hand, conditions like bilateral hemianopia involve visual field deficits caused by factors extrinsic to the visual system, such as a pituitary gland pressing against the optic chiasm, leading to loss of peripheral vision on both sides.