Group 2 Flashcards
For efficient single binocular vision to occur, the retinal images for the two eyes must be in: good focus and of
similar size and shape.
good focus and of similar size and shape.
reviewed the theory of corresponding retinal points developed by Muller, Lotze, Hering, Panum, and other 19th century investigators.
Kenneth Ogle (1950)
According to _____, each light-sensitive element in the retinal mosaic (rod or cone) has a specific local sign: when a particular retinal element is stimulated, the individual experiences a specific subjective visual direction with respect to the directionalization of the fovea.
Lotze
spoke of the visual direction as the subjective direction associated with the fovea when a given object is fixated
Hering (1879)
according to him, when a particular retinal element is stimulated, the individual experiences a specific subjective visual direction with respect to the directionalization of the fovea.
Lotze
Visual direction with respect to the eye.
Occulocentric directionalization
Visual direction with respect to the head
Egocentric directionalization
True or false: If fixation movements are made while the head remains motionless, occulocentric directionalization (for each fovea) does not change, but egocentric directionalization does change.
True
When the two eyes steadily fixate a point in a straight ahead direction.
PRIMARY VISUAL DIRECTION
pairs of points, one in each retina, having the same visual direction and sending their nerve impulses to the same point in the visual cortex.
Corresponding Retinal Points
The visual fields for the two eyes overlap except for the_______ crescents, which are imaged on the______ retina.
temporal; nasal
points have the same visual direction
Corresponding Retinal Points
all points in object space that form images on pairs of corresponding retinal points form an imaginary surface known as
Horopter
usually slightly curved surface, either concave or convex toward the observer
Horopter
According to Ogle, if the corresponding retinal points for the two eyes were symmetrically placed, the shape of the horopter would be____ or known as Vieth-Muller Circle
circle
The shape of the horopter after it is determined experimentally
flatter curvature
for a short distance the horopter is____ toward the observer
concave
for longer distance the horopter is____ toward the observer
convex
for a distance of about 1m (the abathic distance), it is in the form of a ____
flat plane
True or False: The fact that the experimentally determined horopter, does not coincide with the Vieth-Muller circle has been interpreted to indicate that the separation of corresponding retinal points is an equal on the nasal and temporal halves of the retina
True
The method that is most commonly used, providing the most consistent results.
Apparent Frontoparallel Plane Method
The method that is most theoretically correct is that of determining the position of each of a number of points (in the horizontal meridian) so that subjective visual directions of the images formed on the two retinas are identical
Identical Visual Direction
The two methods that Ogle describes in experimentally determining the horopter:
Apparent Frontoparallel Plane Method and Identical Visual Direction
refers to the process by which the images formed on the retina of the two eyes are combined into a single percept
Sensory fusion
often used as a synonym for sensory fusion
Unification
In 1856, Panum demonstrated that within certain limits fusion was possible when the two retinal images of an object were not formed on corresponding retinal points.
Panum’s Fusional Areas
______ dimension of Panum’s fusional areas was somewhat greater than the ______ dimension.
Horizontal; vertical
The horizontal dimension of the panum’s fusional area varied with the ?
peripheral visual angle
In the horizontal width of Panum’s fusional area, a visual angle of 1 degree was approximately
8 minutes of arc
Visual angle of 4 degrees is approximately
12 minutes of arc
Visual angle of 12 degrees is equivalent to __________ minutes of arc
25 minutes of arc
an 8 minute wide fusional area located 1 degree from the center of the fovea would encompass almost_____ cones
300
12 degrees from the center of the fovea is equivalent to ________ cones
140,000 cones
25 minutes of arc is equivalent to ______ rods
2300 rods
Osterberg’s figure
147,300 foveal cones
the fine oscillating movements that the eyes make during fixation
micronystagmus movements
True or false: because of Panum’s fusional area the horopter is not a surface but a solid
True
it occurs when an object is located in front or behind the region of single binocular vision.
Physiological diplopia
According to Lotze and other researchers, the limits of binocular vision must be considered _______
gradient
non corresponding points on the retinas of the two eyes, creates
retinal disparity
A large amount of retinal disparity results
Diplopia
Small amount of retinal disparity results
stereopsis
Ogle characterized streopsis as being _____, whereas monocular clues to the perception of depth are empirical clues that must be _______
innate; learned
predominant clue for the binocular perception of distance
Retinal Disparity
Monocular clues for the perception of distance:
:Size, overlay, geometrical perspective, aerial perspective, light and shadow
large objects are interpreted as being closer than small objects
Size
an object that blocks another object is interpreted as being the closer of the two
Overlay
this is typified by a road or railroad tracks converging towards the horizon
Geometrical Perspective
objects high above the horizon are interpreted as being closer than objects near the horizon
Aerial Perspective
monocular clues are sometimes referred to as empirical clues, and also known as _______, because they are used by artists to convey the illusion of distance.
the picture painting clues
Binocular clues for the perception of distance
retinal disparity, convergence, and accommodation
both eyes move in the same direction
conjugate movement or version movements
the eyes move towards each other or away from the other
disjunctive or Vergence movements
eyes moves toward one another
convergence
eyes moves away from one another
divergence
is a fast, abrupt movement initiated by a sudden increase in innovation to the muscle concerned.
Saccadic
movement to the right
dextroversion
movement to the left
levoversion
According to Burde (1975), saccadic movements are thought to be mediated by the eye fields in the ______ and can occur with a speed as high as ______ degrees per second
frontal lobe (area 8); 400
Saccadic movements can occur as:
- voluntary refixation movements
- involuntary or random movements, or in response to visual or auditory stimuli
- the fast phase in nystagmus
- rapid eye movements occurring in REM sleep
- microsaccades
- pursuit movements faster than 45° per second
is a slower conjugate movement made to keep the image of a moving object on or near the fovea, or to keep the image of a stationary object on or near the phobia as the head moves
Following movement
following movement is located in
Parietooccipital junction (area 19)
which disjunctive (vergence) movement is more highly developed?
Convergence is more highly developed, its amplitude is being 10 times compared to divergence
when the eyes are fixated on a distant object, the total amount of divergent that can be stimulated (by means of base in prism) is no more than about _____ degrees or ____ prism diapers
6; 9.5
when converging towards the nose, in the push up test for convergence, the eyes may converge as much as
60 degrees (95 prism diopters)
the stimuli for vergence movements include the following:
- Changes in accommodation (accommodative convergence)
- Retinal Disparity (disparity convergence or fusional convergence)
- Awareness of nearness of an object (Proximal convergence)
he described convergence movement as involving a gradual increase in the activity of the medial rectus muscles reaching a maximum and gradually declining, with the lateral rectus muscle showing reciprocity throughout the movement
Burde
Burde described _____ movement as involving a gradual _______ in the activity of the ______ rectus muscles reaching a maximum and gradually declining, with the lateral rectus muscle showing reciprocity throughout the movement
convergence; increase; medial
Burde described two types of electromyographic activity for divergence, the first one:
involves as a saccadic burst of firing and both the lateral and medial rectus muscles followed by reciprocal excitation and inhibition of agonist and antagonist
Burde described two types of electromyographic activity for divergence, the second one:
involves an immediate saccadic burst of activity to the lateral rectus muscles with a concomitant inhibition of the medial rectus muscles and followed by irregular activity of both muscles
refers to the vergence movements made by the eyes in response to retinal disparity and having the result of obtaining or maintaining images on corresponding retinal points so that sensory fusion may take place
Motor Fusion
Ogle described motor fusion in terms of what he called the ___&&&
Fusion Compulsion
if a prism, base-out, is suddenly placed in front of one eye while a distant object is fixated, two objects are seen momentarily , but (if not too far apart) they suddenly move toward one another and as if attracted to one another by a magnet like force
The Fusion Compulsion
the process by means of which the optical system of the eye varies its focal length and response to visual stimuli
Accommodation
the process of accommodation is mediated by the _____ , and involves an increase in the vergence of light brought about by the _____
cilliary muscle; crystalline lens
True or False: Accommodation may be specified either in terms of the ACCOMMODATIVE STIMULI or the ACCOMMODATIVE RESPONSE. In clinical work you must deal with the stimulus to the to accommodation because we have no method of knowing at any given moment the accommodative response
True
accommodation may be stimulated in either of two ways:
- near objects
- by the use of minus lens
the stimulus to accommodation is specified in terms of the
diopter
instrument used in research but not ordinarily used clinically, provides a method of measuring the accommodative response?
Haploscope
