Chapter 14 Resting States

Question 1

C14

Give an example of a resting state of the eyes and describe whether all stimuli to all classes of eye movements are absent.

Answer 1

• resting state of the eye would be what the eyes do in the absence of all stimulation to all the eye movement classes
• all stimulation to all the eye movement classes would be absent only in death, this position is truly the resting state

Question 2

C14

Sammy says that because each orbital axis points temporally by 23 degrees from the median sagittal plane, then the anatomical position of rest of the eyes in the absence of neural input is a divergent posture of 46 degrees. Please discuss Sammy’s view.

Answer 2

Sammy clearly needs to reread the chapter and memorize the material a tad bit better…

• vertically there is little to no displacement
• horizontally the eyes adopt a 8 degree divergent posture

Question 3

C14

You would like to measure Maya’s vergence resting level. Other than placing her in a dark room, what other method could you use to obtain the vergence resting level?

Answer 3

• vergence resting position is the horizontal vergence response in the absence of all stimuli to vergence and accommodation
• besides darkness, a empty-field vergence could be used (a bright empty field empty of all details), think of SPY KIDS

Question 4

C14

How do the conditions for measuring tonic vergence differ from those for measuring the heterophoria?

Answer 4

• with heterophoria, the vergence state has cues to vergence: proximity, voluntary effort, and accommodative vergence
• with tonic vergence state all stimuli have been removed except for al weak propinquity (awareness of the dimensions of surroundings)

Question 5

C14

Houston has a vergence resting position of 0.7 MA. Where do his eyes fixate in the dark (meters)?

Answer 5

MA = 1 / d

d = 1 / MA
d = 1 / 0.7 
d = 1.43 meters

His eyes converge to 1.43 meters.

Question 6

C14

Eric has an exophoria. What would you observe as you cover and uncover his eyes?

Answer 6

You would see his eye move back toward center and refixate from the outward position when the cover is removed.