Why Two Eyes ?
You can demonstrate to a patient the difference in their field or their child’s field with one eye compared to two. With two eyes you can also demonstrate the peripheral field and the central fusion.
Why Two Eyes ?
- Total binocular field is nearly 170 degrees (varies according to configuration of orbits)
Two Pencils Test
- With both eyes open the patient who uses both eyes producing stereopsis can put his pencil accurately on the examiner’s pencil if stereopsis is present
- The same person with one eye closed or with manifest strabismus or no stereopsis will miss the examiner’s pencil initially and place it correctly only after the second or third try.
Binocular single vision
Binocular single vision: slightly dissimilar images from both retinas are fused centrally to be interpreted by the brain as a single image.
Stereopsis
Stereopsis: the construction of a 3D percept to the retinal images which have been taken from different angles.
Who needs Stereopsis?
Importance of Stereopsis and Binocular single vision
- Increase field of vision
- Eliminate the blind spot since the blind spot of an eye fall on the opposite eye’s visual field.
- Binocular acuity is greater than monocular
- Depth perception
- Estimation of Distance
