Lecture 3 Flashcards
what do all points along the circumference of the VMO stimulate?
corresponding points and zero binocular disparity
what shape is the theoretical horopter in near vision?
bow-shaped
what are the 3 assumptions for the theoretical VMO horopter?
both retinas are spherical, both retinas have symmetric distribution of local signs across nasal and temporal retinas, and right and left retina are the same size with the same local sign geometry
what is the empirical longitudinal horopter (ELH)?
the actual horopter from experiments on humans - less concave than VMO (flatter)
what is the deviation between the VMO and ELH horopters called?
Hering-hillerbrand deviation
what are the 2 more commonly used methods of measuring ELH?
identical visual direction and equidistance (stereoscopic depth matching)
what are 5 ways to measure ELH horopters?
identical visual direction, equidistance (stereoscopic depth matching), singleness (haplopia), minimum stereoscopic threshold and zero vergence
which horopter method using this: when 2 targets, each presents to one eye, are perceived as lying in a single visual direction, the images of those targets must be formed on corresponding points?
identical visual direction horopter
which method of measuring a horopter is the only true horopter and most accurate? why?
identical visual direction = only one that directly measures the visual direction
when using the AFPP method (equidistance) - what is the percept of the horopter when the rods are physically lined up in a row?
they are perceived as curving away from the observer
when using the AFPP method (equidistance) - what is the percept of the horopter when the rods are physically curved inwards?
they are perceived as being in a straight horizontal line/row
what is the advantage of the equidistance horopter?
examiner can actually see the shape of the horopter directly
what is the disadvantage of the equidistance horopter?
AFPP method doesn’t reflect the effects of fixation disparity, unlike the identical visual direction
which the the most popular way to measure a horopter?
the Howard-Dolman apparatus - using the equidistance or AFPP method
what does the singleness (haplopia) horopter measure?
the extent of Panum’s area at the fovea and eccentric locations
what does the width of the zone of singleness reflect in the singleness (haplopia) horopter?
Panum’s area
what are 2 variables that affect the shape of the ELH?
skew (relative magnification, R) and curvature (hering-hillerbrand deviation, H)