BINOCULAR VISION. FUSION
Definition= State of simultaneous vision with two seeing eyes that occurs when an individual fixes his visual attention on an object. Grades=
➊ Simultaneous perception → power to see 2 dissimilar objects simultaneously – ceases only when we suppress the image from one eye at will
➋ Fusion → Ability of the eyes to produce a composite picture from two similar pictures, each of which is incomplete in a small detail
➌ Stereopsis → Visual appreciation of three dimensions – ability to obtain impression of depth by superimposition of two images of the same object seen from slightly different angle
Advantages=
- Optical defects in one eye are made less obvious by the normal image in the other eye
- Defective vision in one part of the visual field is masked because the same image fall on the functioning area of the other retina
- Field of vision is larger
- Allows individual to converge the line of sight and obtain a reading as to the absolute distance of objects
Approximately 70% of the cells in the striate cortex are binocular cells. Retinal areas from each eye that project to the same binocular cortical cells are called ‘’corresponding retinal points’’.
Fusion= is defined as the unification of visual excitations from the corresponding retinal images into a single visual percept.
➊ Sensory Fusion → the cortical process of blending the images from each eye into a single binocular stereoscopic image
➋ Motor Fusion → the mechanism that allows fine-tuning of eye position to maintain eye alignment – this is known as fusional vergence