Depth perception II Flashcards
What is the benefits of having two eyes
- spare capacity – if one eye gets damaged, we can use another.
- Increased field of vision
- Overlapping fields – important in the generation of binocular vision.
- Increased sensitivity – improves detection of stimulus.
- Stereoscopic depth perception – based on the disparity between the two images formed on the retina.
what is the monocular visual field
155 degrees
what is binocular visual field
120 degrees
what is the total visual field
200 degrees
What is the hierarchy of binocular vision
- Simultaneous vision – the ability to perceive an image with each eye at the same time. (chicken, rabbits)
- Fusion (correspondence stage) – the ability to combine the two monocular images into a single fused binocular image.
- Stereopsis (interpretation stage) – the ability to perceive three-dimensional form in a fused binocular image.
Convergence
when looking at near objects eyes tend to turn inwards converging closer and creating a large angle
less convergence - object further away
high convergence - object close
Fusion
for fusion to occur the images must be located on corresponding retinal areas but also similar in size, brightness and sharpness
sensory fusion - the combination of corresponding retinal images into a single visual percept.
Motor fusion - the ability to align the eyes in such a manner that sensory fusion can take place.
what are the key concepts in binocular vision
corresponding retinal points
the horopter
binocular density
fusion and physiological diplopia
what is corresponding retinal points
Corresponding points on the retina are those positions that receive light rays from objects at the same distance that have a common visual location in space.
What is a horopter
It is a line in space that joins all the positions of all objects that would stimulate corresponding retinal image positions.
what is the empirical horopter
much flatter than the theoretical horopter
Nasal and temporal corresponding points differ in their distance to the fixation point.
Each individual has their own empirical horopter depending on eye position and eye size, shape.
what is the difference between uncrossed and crossed retinal disparity
Uncrossed retinal disparity – objects further away.
Crossed retinal disparity – objects closer.
Define stereopsis
The perception of depth that is produced by binocular retinal disparity
what happens when retinal disparity is too great
Binocular fusion does not occur and images fall on different retinal positions and result in physiological diplopia
What is panums fusional space
a small area around the horopter where objects are seen singly. objects along as they fall on panums fusional space will be fused.
For objects that lie outside Panums fusional space the disparity is too great for images to be fused and the result is physiological diplopia (double vision).
