2. Stereopsis, Stereo means solid or three-
dimensional and opsis means appearnce or sight.
3. Stereopsis
Implies the ability to obtain an impression of depth
by super imposition of two picture of the same object
which have been taken from different angle
Depth perception means the perception of distance
of objects from each other it s a visual appreciation of
three dimensions during binocular vision
4. Test For Stereopsis
1)The TNO stereo test
2)Lang Stereotest II(random dot)
3)Frisby Stereo Test
4) Titmus Fly Test(Polaroid vectograph)
5. (1) The TNO stereo test
It graded to provide retinal disparities ranging from 15 to 480 sec
of arc
it consist of a booklet containing seven plates
Each test plate consists of a stereogram in which various shapes
have been created by random dots in complementary colour
The plates contain two types of figures the one which can be
perceived when viewed binocularly with red green spectacles by
normal subject having stereopsis
The second set of figures can be seen with and without
spectacles even in the absence of stereopsis
6. PROCEDURE
1) Explain the test to the patient: I am now going to
test your 3D vision. Ask the patients to wear the
red/green goggles
2)Ask the patient to hold the booklet at about 40cm
3) Keep the room lights on.
4)For general screening test, the first four plates are
useful as the disparity is large & provides a qualitative
assessment of stereopsis
7. (a) Plate I: two butterflies; one is easily seen
monocularly, the other is only seen in stereopsis.
(b) Plate II: four discs; Two are seen without
stereopsis. Ask the patient: how many circles? Which
is the biggest?
(c) Plate III : four “hidden” shapes(
circle/square/triangle/diamond) are arrange around a
centrally easily visible cross.
(d) Plate IV : Three disc. One seen with right eye, one
seen by left & one seen binocularly.
8.
9. (5) Plate V to VII: grade stereoacuities from 480-15
seconds of arc.
(6)If patients are hesitant about an answer, allow them
plenty of time to view the test plate.
(7) Record the patient’s stereoacuity in seconds of arc.
10. Recording
If the stereo shapes are identified in plates I-III but not
V-VII, record “gross stereopsis”.
If plate IV is incorrect,record which is the suppressing
eye.
For plates V-VII,record the stereoacuity as at least the
highest level where both responses were correct,e.g
“TNO stereoacuity <_ 15”
11. Lang test
This test( Lang,1983) was designed to simplify
stereopsis screening in children.
It is based on two principles; random dots &
cylindrical gratings.
The test is a single card that can be held easily by
yourself or the Pt.
It has three levels of stereopsis, all of which are at a
low level.
12. The test presented at 40cm the pt. has to locate the arc
of the moon(200seconds),a star(200 seconds),a
car(400 seconds) & an elephant(600 seconds).
13. (3) Frisby test
In this test consist of three plastic cards each
containing for squares of small random shape one of
this squares in each plate contains a hidden circle
which is seen disparity
The disparity is created by displacement of random
shapes by the thickness of the plate so this test also
does not require use of glasses
16. The Fly Test
The right side of the test booklet contains a large
housefly to test gross stereopsis
It is especially useful in young children
The asked to pick up one of the wings of fly.
17. The Animal test
It is performed if the gross stereopsis is present
This test consist of tree rows of 5 animal
The subject is asked which one of the animal stands
out
18. THE CIRCLES TEST
It consist of nine squares each containing four circles
arranged in the form of a lozenge
Only one of the circles in each square is disparately
imaged at random with threshold ranging from 800 to
40 sec of arc
If the subject has passed other two test, he asked to
push-down the circle that stands out, beginning with
the first set.
