VT for Stereopsis

Question 1

What effect would a BO prism have on the perceived size of a real object?

Answer 1

Object would be perceived as smaller. The vergence system causes the line of sight to converge in front of the object, creating the perception of nearness. Since the actual object takes up the same amount of retinal image space, the perception is that the object must have gotten smaller as it got “closer.”

Question 2

What effect would a BI prism have on the perceived size of a real object?

Answer 2

Object would be perceived as larger. The vergence system causes the line of sight to converge behind the object, creating the perception of farness. Since the actual object takes up the same amount of retinal image space, the perception is that the object must have gotten larger as it got “further away.”

Question 3

Of the following list, all cause an increase in stereoscopic 3D-related symptoms except two. Which two are the exception?

Vestibular interaction and disorder
Neuromuscular disorder
Prebyopia
Sedentary lifestyle
Medications
Immersion
Accommodation or vergence disorders

Answer 3

Presbyopia and immersion both decrease the symptoms of stereoscopic 3D.

Question 4

Training stereoscopic 3D can be done by training the following:
Awareness of float
Localization of floating image
Localization comparison of two floating images
The above steps, but at far now.

Answer 4

Free card.

Question 5

A Marsden ball and polarized quoits transparencies can be used to train what?

Answer 5

Awareness of float.

Question 6

How can a vectogram be used to train localization of float?

Answer 6

Wearing the polarizers, the patient places a pointer in their line of sight. If the patient is focusing on the float from the vectogram, the pointer will appear doubled unless it is perfectly lined up with the plane they are focused on. This allows them to move the pointer and appreciate the location of the float.

Question 7

What sorts of activities can a patient do with double vectograms in order to appreciate float even more?

Answer 7

They can used polarized flippers while one vectogram is set to a BO demand and the other is set to a BI demand. This allows them to compare out-float and in-float. They can also modify one of the vectograms to the other in trying to match the float.

Question 8

What is the name of the instrument that is used to try and appreciate float at infinity? (Hint, this instrument involves a septum and +5.00D lenses to relax accommodation.)

Answer 8

Brewster stereoscope