Ch 14: Resting States Flashcards
anatomical position of rest is defined as
the position of the eyes when all innervation is suspended (thought to occur soon after death)
vergence resting position is the
horizontal mergence response in the absence of all stimuli to mergence and accommodation
what is vergence resting position also known as
tonic vergence
how can vergence resting position be measured
as dark vergence (while viewing in complete darkness) or empty-field vergence (bright field empty of all details)
what is the average vergence resting position in MA? what is the range?
average is 0.86 MA, with a range of 0-2 MA
what is occurring when MA=0?
eyes are converging at infinity
what vergence can still remain in measurements in darkness and why?
vergence can still remain because people usually remain aware of the dimensions of their surroundings, even in the absence of visual stimuli (propinquity)
what is propinquity and how can we overcome this effect?
awareness of the dimensions of surroundings, even in the absence of visual stimuli, we would have to lead a person into an unfamiliar testing room blindfolded
what does a fusion-free position correspond to?
heterophoria
what are common heterophorias
esophoria, exophoria, and small vertical heterophorias
esophoria is
an inward posture
exophoria
an outward posture
how do you check esophoria by the cover test?
when one eye is covered, the disparity stimulus to vergence is removed. the eye under the cover turns in. when the cover is removed, the eyes take up normal fixation again
what is a Ganzfeld viewing condition and what is an example of how it can be achieved?
ganzfeld can be obtained in dense fog
empty field vergence, bright field empty of all details
