Introduction to Binocular Vision

Question 1

___% of the cerebral cortex devoted to visual processing

Answer 1

50%

Question 2

Describe the importance of monocular vision

Answer 2

• Provides information to identify & recognize objects “the what part”
• Provides information about visual direction, motion, & depth perception “the where part”
• Depth cues - linear perspective, occlusion, elevation, texture gradients & motion parallex

Question 3

Define Binocular Vision

Answer 3

• combined input from two eyes significantly enhances “what” and “where” part of objects ⇒ Binocular summation
• Greatest contribution in our perception of “where” objects are located, especially enhancing our perception of visual direction & depth perception

Question 4

Why is the study of BV important?

Answer 4

• Managing pt w/ complaints of eyestrain, HA, difficulty reading, convergence insufficiency, strabismus, etc.
• Visual development & pediatric vision/optometry
• Vision therapy
• Monovision (CL lens)
• Driving

Question 5

What are the advantages of binocular vision?

Answer 5

• Two eyes are better than one

1. Spare eye - in case one gets damaged
2. Wider field of vision (MAJOR BENEFIT)
3. Binocular summation
4. Stereopsis (MAJOR BENEFIT)
5. Other enhancements to visual performance

Question 6

Monocular VF (Measurements in degrees)

Answer 6

• Without eye movements, the monocular VF is about 150º
• From point of fixation, stimuli can typically be detected - 60º superiorly, 70º inferiorly, 60º nasally, 100º temporally

Question 7

Binocular VF (degrees for OU and overlap)?

Answer 7

• 180º wide w/ both eyes
• considerable overlap of the two VF in the forward direction, binocular field is 120º

Question 8

Wider field of view

Answer 8

• Lateral to the binocular field are crescent shaped monocular V (seen by one eye alone) are called temporal crescent
• the total width of VF using both eyes & width of the overlapped binocular VF are determined by the position of the eyes in the head (intraocular distance 60-65mm)

Question 9

Binocular Summation

(Define, What is enhanced?)

Answer 9

• Additivity of the information from each eye, to yield binocular visual performance (that exceeds monocular performance)
• Certain aspects of vision are improved because of the input provided by the second eye, although small improvement.
• Binocular summation enhances
  
  • Light detection threshold
  • Contrast sensitivity
  • VA
  • Color vision, hand-eye coordination, depth & motion perception
• ​Greater sensitivity makes things which are small, dimmer, quicker more detectable

Question 10

What is considered as the most significant advantage gained by binocular vision?

Answer 10

• Stereopsis - highly accurate sense of depth perception that is unique to binocular vision
• Determines the position of the object around us relative to our position, and to determine our position relative to our environment
• Subtle differences between the images in each eye

Question 11

What is the biggest disadvantage when using monovision CL?

Answer 11

• can lead to misconception of the distance betwen the aircraft & the runway during approaching
• cause degraded depth perception

Question 12

Other enhancements to vision performance (Children)

Answer 12

• Bioncular vision provides better space perception, hand-eye coordination, more efficient, comfortable reading
• Children who have had their strabismus corrected (there by allowing for BV) are often reported to have better & improved visual-motor skills such as hand-eye coordination

Question 13

Disadvantages of BV

Answer 13

• Three eyes would give us better stereopsis than two eyes, but it is not always better to have more. (Trinocular imaging system)
• video capture systems can be perfectly aligned
• Biological systems are not precise & misalignment can cause problems such as diplopia
• input from 2 eyes is more complex than 1, w/ greater complexity = more problems
• Binocular anomalies can cause sx such as eyestrain, HA, or difficulty reading

Question 14

Binocular stress can be caused by

Answer 14

• incorrect refractive balance
• Dissimilar images between the 2 eyes due to aniseikonia
• convergence insufficiency or convergence excess
• conflicts between accommodation & convergence

Question 15

Misalignment betwen the 2 eyes incorrectly can produce… ?

Answer 15

Strabismus (eye turn)

Amblyopia (Reduce spatial vision)

Suppression

Diplopia

Question 16

How do you treat intractable diplopia?

Answer 16

Occlude one eye, interrupt binocular vision by prescribing an eye patch. This prevents binocular fusion & renders pt monocular. The binocular system can cause more problems than it can benefit.

Question 17

The more eyes you have, the more ____ you need.

Answer 17

Neural circuitry to process the information

Although, it can help with better acuity & contrast perception, the advantage is not that great.

Question 18

Misconceptions about binocular vision

Answer 18

Stereopsis is not the only advantage

Depth perception is still possible with one eye, there are many monocular cues that allow judgement in depth perception. Monocular depth perception is superior to binocular depth perception.

Stereoscopic depth perception does not help judge depth of far objects (ex. plane, driving)

Question 19

Requirements for Binocular Vision

Answer 19

• Two eyes separated intraocularly (65mm in adults)
• neural pathway to transfer visual info to the brain
• Neural processing system to integrate & analyze raw visual info (size, illumination, contrast, color, movement relative to the eye etc.)
• EOM allow the fixated objects to be imaged on the retina
• Motor control systems to govern voluntary & reflex eye movements
• Head & body mvmts & monocular cues to the total perception

Question 20

Frogs binocular vision

Answer 20

• almost 360 degrees
• Panoramic vision
• little or no overlap of VF

Question 21

T/F: Having two eyes enlarges the field of view, but also more pronounced in predatory species.

Answer 21

F. Less prounounced in predatory species