eye test used for depth perception

1. Stereopsis

2. Stereopsis
• This is the ability to perceive two slightly
dissimilar image, one formed on each
retina, and to blend them as one with the
perception of relative depth on the basis
of this image disparity.
• Special tests are used to access
stereopsis
• It also accessed by synaptophore using
slides of stereopsis.

3. History
• Stereopsis was first explained by Charles Wheatstone
in 1838: “… the mind perceives an object of three
dimensions by means of the two dissimilar pictures
projected by it on the two retina …”. He recognized
that because each eye views the visual world from
slightly different horizontal positions, each eye's image
differs from the other. Objects at different distances
from the eyes project images in the two eyes that
differ in their horizontal positions, giving the depth cue
of horizontal disparity, also known as retinal disparity
and as binocular disparity. Wheatstone showed that
this was an effective depth cue by creating
the illusion of depth from flat pictures that differed
only in horizontal disparity. To display his pictures
separately to the two eyes, Wheatstone invented
the stereoscope.

4. Types of steriopsis
• Coarse stereopsis (also called gross stereopsis)
appears to be used to judge stereoscopic motion in the
periphery. It provides the sense of being immersed in
one's surroundings and is therefore sometimes also
referred to as qualitative stereopsis.[5] Coarse
stereopsis is important for orientation in space while
moving, for example when descending a flight of stairs.
• Fine stereopsis is mainly based on static differences. It
allows the individual to determine the depth of objects
in the central visual area (Panum's fusional area) and is
therefore also called quantitative stereopsis. It is
typically measured in random-dot tests. Fine stereopsis
is important for fine-motorical tasks such as threading
a needle.

5. Functional life and
stereopsis
• needle-threading
• ball-catching
• pouring liquids
• Using stairs
• shopping
Professional activity may involve
• operating stereoscopic instruments such as a
binocular microscope
• airplane pilots
• Surgeons normally demonstrate high stereo
acuity. As to Car driving,

6. Absence of steriopsis
• High-grade stereopsis confers an
advantage when performing a fine
motor task under direct vision.
However, stereopsis does not appear
advantageous to task performance
under 2D viewing conditions, such as
in video-assisted surgery.

7. • Performance on motor skills tasks was
related to stereoacuity, with subjects
with normal stereoacuity performing
best on all tests. This quantifiable
degradation in performance on some
motor skill tasks supports the need to
implement management strategies to
maximize development of high-grade
stereoacuity.

11. Assessment of stereopsis
i. Two pencil tests for stereopsis to
check gross stereopsis
ii. Titmus stereo test
iii. Lang I and Lang II stereo tests
iv. TNO random dot test

12. Titmus stereo test
Recognized as the standard for Stereo Depth Perception
testing,
It allows evaluation of both gross and fine stereo vision.
Easy to perform
Polarized glasses are used to perform test
The test includes:
A fly for gross stereopsis (3000 seconds of an arc)
Graded circle test (800 to 40 seconds of arc)
Animal test (400 to 100 seconds of arc)

13. LANG-STEREO TEST
• Measures stereo acuity between 1200
and 200 seconds of an arc.
• The LANG-STEREO TEST is an easy-to-
use
• No spectacles are required
• Screening-test designed for early
detection of problems with sterescopic
vision in children.

14. Lang I and Lang II test

15. • Two versions of the test plates are
available, which differ only according to
the 3D objects to be recognized.
• The LANG-STEREOTEST I displays a star,
a cat and a car
• LANG-STEREOTEST II displays a moon, a
truck and an elephant, each of them
appearing on a different level.
• In addition, the LANG-STEREOTEST II
contains a star that can be seen with only
one eye.

16. Frisby stereo test
• Consist of 3 transparent plates of
varying thickness
• It measures stereo acuity between
600 and 15 seconds of an arc
• Does not require any spectacle
• Based on the actual depth of target,
disparity is created by the thickness of
plate

17. Frisby stereo test

18. TNO random-dot tests
• Consist of seven plates each of which
contains various shapes created by
random dots in complementary colors
which are viewed through red green
goggles.
• First tree plates are to check the
presence of stereopsis other are to
quantify it.
• It measures 480 to 15 sec. of an arc

19. TNO test plates
• Plate I: 2 butterflies are present, one can be seen
monocularly, the other is only seen in stereopsis.
• Plate II: 4 discs, 2 are seen monocularly two
require stereopsis.
• Plate III: four hidden shapes (O, , , ) are
arranged around a centrally placed cross
• Plate IV: This is a suppression test. There are 3
discs, one seen by the right eye, one by the left,
and one is seen binocularly.
• Plate V-VII: Here the test items (Pac-man
Shapes) are presented at 6 different disparities
ranging from 15 – 480 sec. of arc.

21. It is noted as..
• Steriopsis is notes as the seconds of
arcs perceived by patients during
different test.
• Normal stereoacuity is 60 sec. of arc

22. PRESCRIPTION OF STEROVISION
• Yoke prisms(which non-specialist
optometrists donot even
prescribe)...improved depth
perception...Gregg went from bottom of the
batting order in baseball to top.
• Treatment For Stereo Blindness
Patient with stereo blindness require
optometric vision therapy,including the use of
prism and 3D glass.Treatment duration will
depends upon the patient condition.

23. • In the case of acquired strabismus with
double vision(diplopia),it is long-established
state of the art to aim at curing the double
vision and at the same time recovering a
patients earlier ability for stereo vision, For
example a patient may have had full stereo
vision but later had diplopia due to a medical
condition including vision therapy and
strabismus surgery,may recover thr double
vision and recover the stereo vision which
had temporarily been absent in the patients.

24. References
• http://iovs.arvojournals.org/article.aspx?articleid=21
85960
• https://books.google.com/books?isbn=142891681
• www.visiontherapy.ca/3dmediaandvision.html
• file:///C:/Users/ASUS/Downloads/Stereopsis%20-
%20Wikipedia,%20the%20free%20encyclopedia.htm