1 & 2. Intro To Binocular Vision & BV problems Flashcards
Benefits of binocular vision
- Increased field of view.
- Compensation for the phycological blind spot.
- Binocular summation
- Stereopsis (depth perception)
What is the term used to describe double vision?
Diplopia
What causes double vision?
When the eyes are not lined up, different images fall on each fovea in both eyes (this is called confusion). This 2 images are superimposed leading to double vision- because the 2 images are seen together at the same time.
How is alternating vision caused? And it can lead to ?
Due to double vision, the brain uses image from 1 eye at a time causing an alternation between the 2 images, leading to loss of peripheral vision.
What is stereopsis?
Depth perception or 3D vision
What do we need to have binocular vision?
Two eyes with overlapping visual field
What 4 factors are important for optimal binocular vision?
Good VA
Roughly equal VA
Roughly equal sized images
Clear media- no cataracts
Where does binocular visual processing take place pathway and why does it need to be intact?
Processing takes place in the cortex (brain) hence needs to be intact.
BV processing takes place in the brain and not they eye.
What ocular conditions are caused if binocular vision pathway isn’t intact?
Albinism -not all information cross optic chiasma it stays on the same side of the brain.
What motor aspect is important for BV?
Positioning of the eyes to look at an object and maintaining alignment at the object
What voluntary and involuntary muscles play a role in motor aspects of BV?
Voluntary- extraocular (extrinsic) muscles
Involuntary- ciliary muscles (Accommodation) and pupils (sphincter and dilatory)
Is binocular vision present at birth?
NO
Binocular vision develops at what age?
It first rapidly develops over the first 6 months of life and continues for 8/9 years of life
At what age is binocular vision the most malleable?
Up to 5/6 years, maybe up until 8/9 years, very difficult to change after this
Where does binocular vision processing occur?
In the brain (in V1 of the occipital cortex and subsequently in the higher centre) and this route is provided by the retina to co-ordinate information
Describe how binocular vision processing occurs in relation to ganglion cells and the cortex
Info from ganglion cells at corresponding points in each eye are processed together in the cortex to extract binocular information. Decussation of nerve fibres at chiasm allows this.
Define principal visual direction/ visual axis/ line of sight?
(When looking at an object), the image falls on the fovea and lies on the visual axis.
Define secondary visual direction
Image does not fall on the fovea. (Surrounding objects)
Define oculocentric localisation
Position of objects relative to principal visual direction in monocular vision.
Define egocentric localisation
Understanding position of objects relative to our bodies. (using both eyes and proprioceptive clues).
Define primary visual direction and it is determined by?
It is determined by the eyes rotation. Image will fall on the fovea even if that object is not at the centre of the scene.
Multiple objects in the same visual direction are perceived as?
Being behind or in front of each other.
Difference in images between 2 eyes is called?
Retinal Disparity
Define Horopter
Imaginary plane for a fixation point. All objects on this plane perceived as single.
