This document discusses various tests used to evaluate stereopsis and depth perception. It describes: 1. Tests of gross stereopsis like the pencil test that evaluate the ability to perceive depth with both eyes open versus monocularly. 2. The Frisby and Randot stereotests that use displaced shapes or dots seen through polarized lenses to test fine stereopsis. 3. Administration and passing criteria for the TNO and Lang stereotests which use random dot patterns to evaluate minimum stereoacuity. 4. The Fly test and Titmus test which similarly use vectographic images seen through polarized lenses but include shapes of increasing difficulty to measure fine stereoacuity.

1. Fakhruddin Aliasger
Lecturer
SPIO
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2.  Depth may be perceived in two forms
 1. Binocular Disparity (stereopsis)
 2. Monocular Depth Clues
 Stereopsis is the perception of the relative
depth of objects on the basis of binocular
disparity which reflects the slight difference
in the image presented to each eye
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3.  Stereoacuity is the angular measurement of
the minimal resolvable binocular disparity,
which is necessary for the appreciation of
stereopsis
 The ability to demonstrate stereopsis
indicates the presence of retinal
correspondence
 The normal level of stereopsis being
40seconds of arc
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4.  This is a test for gross stereopsis
 The patient attempts to place a pencil on top
of one held by examiner
 Patient who possess stereopsis will find it
easier to perform the test with both eyes
open than monocularly
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7.  This uses random shapes with displacement
and consists of three plastic plates of
different thickness of 6mm, 3mm and 1mm
 Each plate consists of four squares produced
by random shapes printed on one side
 Corresponding to one of the squares a
disparity is produced
 This disparity creates a 3D appearance of a
circle
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8.  Frisby plates held at a distance of 40cms of
6mm, 3mm and1mm thick produces
stereopsis of 340”, 170” and 55” respectively
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9.  Random dot stereogram test comprise
images, formed of dots which are displaced
in relation to each other
 The space created by this is filled randomly
by dots
 Those seen by one eye have no relation to the
other eye
 This produces disparity of viewing as both
eyes will see different dots
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10.  There are two types of Random dot test
 1. Lang stereotest
 2. TNO stereotest
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11.  The Lang-stereotest was developed by the
Swiss ophthalmologist Joseph Lang in the
beginning of the eighties
 Two versions are available Lang-stereotest I
and II which only differ in the type of
stereoscopic objects to be recognized
 The Lang-stereotest II additionally contains a
picture that can be recognized with one eye a
star
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12.  The Lang-stereotest for the first time
combines two functional principles of
stereograms the random dots of Julesz and
the grid of cylinders of W.R. Hess
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13.  Position yourself in front of the examinee, so
that you can easily observe his/her eye
movements
 Show the test plate exactly at right angles at
a distance of about 40 cm (16 inches)
 Ask the child if he/she sees something on the
plate and watch the searching movements of
his/her eyes
 When a 3D object has been detected, ask the
child to look for additional objects and also
to describe them
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14.  The examinee may then also point at the
figures and should be able to tell which of
them sticks out most
 Disparities Lang test I
 Car: 550”
 Star: 600”
 Cat: 1200
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15.  Disparities Lang test II
 Moon: 200”
 Truck: 400”
 Elephant: 600”
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17.  Positive
 Correct localization and naming of all hidden
objects, typically jumping eye movements from
one object to the next
 Negative
 No object can be detected, and eye movements
also do not indicate the recognition of the 3D
objects
 Eyes are scanning the test plate and then shift
away from it
 Doubtful
 only one hidden object is localized and named
correctly, eyes are scanning the plate for objects.
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18.  This test was primarily designed for screening
pre-school children for defects of binocular
vision
 It consists of seven plates to be viewed with
red – green spectacles that carry figures that
can be seen only when both eyes cooperate
to give stereoscopic vision
 Three plates (plate I-III) enable the examiner
to quickly establish whether stereoscopic
vision is present at all
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19.  The three plates (V-VII) may be then used for
exact determination of stereoscopic
sensitivity
 When used for screening plate V should be
used as pass fail criterion
 Plate V measures stereoacuity of 480-240 sec
of arc
 Plate VI measures stereoacuity of 120-60 sec
of arc
 Plate VII measures stereoacuity of 30-15 sec
of arc
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20.  When administrating the test plates should be
well illuminated
 The test should be carried out at a distance of
40cms
 The plate should be held squarely and should
not be rotated
 Red green goggles should not be removed
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21.  Plate I
 In this plate two butterflies can be seen, but
one of them is hidden that is visible only
when both eyes are used
 The child is asked to point out at each
butterfly it can see
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23.  Plate II
 Four discs (balls, saucers), that differ in size
are present
 Two of these the largest and second smallest
are visible only stereoscopically
 First ask for the smallest disc which always
visible and then for the largest
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24.  Plate III
 It consists of four hidden item a disc,
triangle, square and diamond are arranged
around a central cross of different texture
 The child is first asked to look for an example
on the opposite page and then asked to find
for the corresponding plate
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26.  Plate IV
 This is a suppression test
 It consists of a small disc and two large disc
each flanked on sides
 If a child sees only two disc one big and one
small it indicates presence of suppression
 Big disc seen in front of which eye
corresponds to dominant eye
 If the child shows the ability to see small disc
fused with one of the large disc it indicates
presence of fusion
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27.  Plate V-VII
 Here the test figures disc with a sector
missing are presented at six different level
 The corresponding retinal disparity ranges
from 15 to 480 sec of arc
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28.  It is based on the principle of linear
polarisation
 Polaroid filters are worn and a vertical image
of a light source is seen through one filter
and a horizontal image of light is seen
through the other filter
 The target are presented as vectographs
 The disparirty produced by either eye results
in stereopsis
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30.  One plate contains the image of a fly
 The second plate consists of nine boxes each
containing four circles and three rows of
animals
 One circle is displaced to produce disparity
 The image of one animal in each row also
appears to stand out
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31.  The patient wears his/her correction and
wears polaroid lenses over it
 The patient is first shown the fly
 The patient is asked to catch the fly by its
wings
 If the fingers reach above the plates patient
has stereopsis if not the finger will touch the
plate
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32.  In the second part of the test there are three
rows of animals
 The patient is asked to push down the animal
that stands out
 The third part of the test consists of nine
squares with four circle in each of square
 In each square one of the circle appears to
stand out which the patient is asked to push
down
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33.  This test is based on the principle of linear
polarisation
 This test is similar as titmus fly test having
three parts
 On one plate it consists of two groups of four
square
 Three of which it contains geometric shapes
which includes circle square and star
 The shapes appear to stand out distinctly
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35.  The other plate consists of animals and circle
similar to that of titmus fly test
 The perception of random shapes gives
stereoacuity of 500-250 sec of arc
 The perception of circle and animal shapes
gives stereoacuity of 400-20 sec of arc
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