Retinal correspondence

RETINAL CORRESPONDENCE
OPTOM FASLU MUHAMMED

RETINAL CORRESPONDENCE
 Retinal elements of the two eyes that share a common
subjective visual direction are called corresponding
retinal points

LAW OF SENSORY CORRESPONDENCE
 The existence of corresponding retinal elements with
their common relative subjective visual directions is the
essence of binocular vision

SENSORY FUSION
 The unification of visual excitations from corresponding
retinal images into a single visual percept, a single visual
image

 An individual cannot see double with corresponding
retinal elements.
 Single vision is the hallmark of retinal
correspondence.
 Double vision is the hallmark of retinal disparity

 For sensory fusion to occur, the images not only must be
located on corresponding retinal areas but also must be
sufficiently similar in size, brightness, and sharpness.

 Unequal images are a severe sensory obstacle to
fusion.
 Obstacles to fusion may become important factors
in the etiology of strabismus.
 Differences in color and contours may lead to
retinal rivalry

MOTOR FUSION
 The ability to align the eyes in such a manner that
sensory fusion can be maintained
 motor fusion is the exclusive function of the extra foveal
retinal periphery

RETINAL RIVALRY
 When dissimilar contours are presented to
corresponding retinal areas, fusion becomes
impossible.
 Instead, retinal rivalry may be observed.
 This phenomenon, also termed binocular rivalry

 Simultaneous excitation of corresponding retinal
areas by dissimilar stimuli does not permit fusion;
 but since such excitations are localized in the same
visual direction and since two objects localized in
the same place give rise to conflict and confusion,
one or the other is temporarily suppressed

HOROPTER
 Aguilonius
 Helmhotz

PHYSIOLOGIC DIPLOPIA
 On EH – single
 Not in EH – double

STEREOPSIS
 the relative ordering of visual objects in depth, that is, in
the third dimension

 The greater the depth effect, the greater the horizontal
disparity

MONOCULAR CUE
 Non-stereo depth cue
 One eye can judge its
 Patients with binocular vision defect  still can feel the
depth perception

MONOCULAR CUE
 Occlusion  near objects block the view of
distant objects
 Apparent size  if two objects are actually
the same size, but one appears smaller,
then the small one is farther away than the
larger  relative size
 Motion parallax and Relative velocity
near objects appear move faster than
distant objects
 Light and Shading  distance and colour
 Overlapping contour*

MOTION PARALLAX
 Translocation of the head
 Cause the images of near objects to move opposite
the head
 The images of far objects to move with the head
 Assuming the fixation point is at an intermediate
distance

MONOCULAR CUE
Perspective  parallel lines converge in
the distance
Aerial perspective
Geometric perspective
Texture  becomes finer with distance
Colour change  colour becomes more
blue with distance  Atmospheric effect
Haze  objects become fuzzy in the
distance
Accommodation  our brain knows
how hard our eyes are working to focus

DEPTH PERCEPTION
 Monocular cues
 Non stereoscopic binocular clues
 Stereopsis

WHY FOVEA/PERIPHERY DIFFERENCES
 Range of disparities in natural scenes.
 Fovea - high depth acuity.
 Periphery - provides coarse information about
where to make convergence eye movements.

MISTAKE IN BSV
• Motoric
– Squint
• Refractive
– Aniseikonia
• Eye Sensoric
– Amblyopia
• Optical problems
– Visual illusion
• Brain Perception
– Experience
– Monocular cues
– Visual illusion

VISUAL ILLUSION: SHADOW EFFECT

VISUAL ILLUSION: MOVING TEXTURE

VISUAL ILLUSION: GRID ILLUSION

VISUAL ILLUSION: FLOOR PAINTING

VISUAL ILLUSION: MIRAGE
A superior mirage occurs when the
air below the line of sight is colder
than the air above it.
A inferior mirage occurs when the air
below the line of sight is hotter and
has lower index bias than the air
above it.

MIRAGE: HOT HAZE
Heat shimmer  refers to the inferior mirage
experienced when viewing objects through a
layer of heated air

VISUAL ILLUSION: HALO
A sun dog (or sundog), mock sunor phantom
sun, scientific name parhelion (plural
parhelia), is an atmospheric phenomenon
that creates bright spots of light in the sky,
often on a luminous ring or halo on either
side of the sun.
Sundogs may appear as a colored patch of
light to the left or right of the sun, 22° distant
and at the same distance above the horizon as
the sun, and in ice halos.
They can be seen anywhere in the world
during any season, but they are not always
obvious or bright.
Sundogs are best seen and are most
conspicuous when the sun is low.

SUNSET GREEN FLASH
The optical phenomenon known as the green
flash can occur at sunrise or sunset, and it’s
most often seen over low, unobstructed
horizons such as the ocean.

SUN PILLAR
A Sun pillar is an atmospheric phenomenon
caused when high-altitude ice crystals reflect
the rising or setting Sun’s reddened light.

SCINTILLATION OR GRID ILLUSION

VISUAL ILLUSION: OPTIC
1. Thermal Inversion
The Titanic was sailing from Gulf
Stream waters into the frigid
Labrador Current, where the air
column was cooling from the bottom
up, creating a thermal inversion:
layers of cold air below layers of
warmer air.
Extraordinarily high air pressure kept
the air free of fog.

2. Superior Mirage
A thermal inversion refracts light
abnormally and can create a
superior mirage: Objects
appear higher (and therefore
nearer) than they actually are,
before a false horizon.
The area between the false
horizon and the true one may
appear as haze.

3. Iceberg Camouflage
The Californian’s radio operator
warned the Titanic of ice. But the
moonless night provided little
contrast, and a calm sea masked the
line between the true and false
horizons, camouflaging the
iceberg.
A Titanic lookout sounded the alarm
when the berg was about a mile
away—too late.

4. Mistaken Identity
• Shortly before the collision, the
Titanic sailed into the Californian’s
view—but it appeared too near and
small to be the great ocean liner.
• Californian captain Stanley Lord
knew the Titanic was the only other
ship in the area with a radio, and so
concluded this ship did not have one.

5. Morse Lamp
• Lord said he repeatedly had
someone signal the ship by
Morse lamp “and she did not
take the slightest notice of it.”
• The Titanic, now in trouble,
signaled the Californian by
Morse lamp, also to no avail.
• The abnormally stratified air was
distorting and disrupting the
signals.

6. Distress Rockets Ignored
• The Titanic fired distress rockets
some 600 feet into the air—but
they appeared to be much lower
relative to the ship.
• Those aboard the Californian, unsure
of what they saw, ignored the
signals.
• When the Titanic sank, at 2:20 a.m.
April 15, they thought the ship might
be simply sailing away.

CONFLICTING CUES: ONLY BINOCULAR
 Random Dot Stereograms

3D ABILITY: 3D MOVIE
The archetypal 3D glasses, with modern red
and cyan color filters, similar to the red/green
and red/blue lenses used to view early
anaglyph films.

Resembling sunglasses, polarized glasses are
now the standard for theatrical releases and
theme park attractions.

A pair of LCD shutter glasses used to view
XpanD 3D films. The thick frames conceal the
electronics and batteries

BEYOND THE LECTURE
 I have seen with my own eyes!
 So now…
 What do you think?
 Seeing doesn’t mean believing
 Think again!

Retinal correspondence

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Retinal correspondence