1. Review of BSV
SENSORY EVALUATION OF
STRABISMUS
Gauri S. Shrestha, M.optom,
Lecturer
Deepa Dhungel, B.Optom II year

2. Normal Binocular Vision

3. • Monocular: 160°(w)X175°(h)
• Binocular: 200° (w)X175°(h)
• Region of binocular overlap: 120° (w)X135°(h)

4. visual field
Prerequisite for BSV
• Separate fields of vision must
overlap in all direction of
gazes.
• Separate fields of fixation
must overlap with coordinated
movements of the two eyes.
• Neural transmission from the
two eyes must reach the same
area of brain.
• Perceptual co-ordination must
take place.

5. Corresponding retinal points
• Every retinal point or
area has a partner in the
fellow retina with which
it shares relative
subjective visual
direction

6. Horopter
• “Locus of all the object points that are imaged
in corresponding retinal elements at a given
fixation point”

9. Panum’s fusional area
• The region around the horopter that’s allows
single vision.
• Object stimulates slightly non- corresponding
points
• Objects are not only seen single, but are seen
stereoscopically.

11. Physiological diplopia
• The diplopia elicited by an object off the
Panum’s fusional area
• Types
– Crossed (heteronymous) diplopia
– Uncrossed (homonymous) diplopia

13. Grades of BSV
• 1 – simultaneous perception
• 2 - superimposition
• 3 – flat fusion
• 4 - Stereopsis

14. Simultaneous perception
• Is the most elementary type of binocularity
• Occurs when the visual cortex perceives
separate stimuli to the two eyes at the same
time and concerns itself essentially with the
absence of suppression.

15. • The two different pictures are seen
simultaneously in the same direction
• Differing targets are the superimposed into
one
2 - superimposition

16. • Cortical unification of visual stimuli into
a single percept after simultaneous
stimulation of corresponding retinal
areas.
• The objects must be similar in shape
and size
3 – flat fusion

18. 4 - Stereopsis
• It is the ability to fuse images that stimulate
horizontally disparate retinal elements within
Panum’s fusional area resulting in binocular
appreciation of visual object in depth i.e. in the
third dimension
• Stereopsis occurs when
– Retinal disparity is large enough for simple fusion
but small enough not to cause diplopia

20. Abnormal binocular vision
• Sensory adaptation
– Confusion
– Diplopia
– Supression
– Ecccentric fixation
– Anomalous retinal correspondence (ARC)
– Amblyopia

21. Diplopia /Confusion

22. Introduction - Suppression
• Cortical inhibition of visual sensation that
originates from spatially abnormal eye to
eliminate the problem of visual confusion and
diplopia.
• Pathologic suppression results from strabismic
misalignment of the visual axes
• Physiologic suppression occur in eyes with
BSV

23. Patient without suppression

24. Classification of suppression
• Physiologic v/s Pathologic
• Central v/s peripheral
• Monocular v/s alternating
• Facultative v/s obligatory

25. 3. ARC
• Sensory anomaly where the fovea of the
fixating eye and a non-foveal site of the
deviating eye have a common visual
direction
• Objective angle(<H)–
• Subjective angle(<S)–
• Angle of anomaly (<A)

26. Types
A= H-S
• No anomaly
• Harmonic ARC
• Unharmonic ARC
• Paradoxical ARC I & II

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Types of ARC
• Harmonious ARC;
– Angle of anomaly(A)=
objective angle (D)
– (S)=0

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• Unharmonious ARC
– Subjective angle(S) is
less than Obj angle
but greater than
zero.
– Angle of anomaly not
equal to the obj
angle

29. Eccentric fixation
• The fovea has lost its principal visual direction
• Px reports that they are looking straight at an
object stimulating non foveolar retinal area
• Types
– Foveal off-center ---1 degree or less (> 0 degrees)
– Parafoveal---3 degrees or less (> 1 degree)
– Paramacular---5 degrees or less (> 3 degrees)
– Peripheral---Greater than 5 degrees

30. Tests for Sensory Anomalies

31. Worth Four-Dot Test
• a gross test which provides
information only about the
status of peripheral
binocular cooperation
• Harmonious ARC= 4 lights
(Deviation)
• 2 lights (Left suppression)
• 3 lights (right suppression
• 5 lights (Diplopia)

32. Bagolini striated glasses
• The Bagolini lenses
have fine barely visible
striations, oriented at
135 degrees before the
right eye and 45
degrees before the left
eye

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Bagolini striated glasses test
NRC/ HAC UAC, Esotrope
,
UAC, Exotrope
Vertical ARC

34. 4 prism base out test
• Usually determines
whether a patient has
bifoveal fixation or a
small suppression
scotoma.
• A 4 prism dioptre base
out prism is placed
infront of one eye & a
biphasic movement of
the fellow eye is noted.

36. Vectographic tests
• Polarised charts seen with polarising lenses
• One eye sees half of the chart and the other
sees the other half
• Polamirror
• Looking into the mirror while wearing
polarising glasses
• No suppression both eyes seen
• With suppression only one eye seen

37. • an instrument for the
assessment of
strabismus and the
grade of binocular
vision
Synoptophore

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Vectographic slide
• Subjective angle
calculated and
compared with
objective angle

40. Binocular Perimetry and Haploscopy
• use of one form of color differentiation, such
as red-green spectacles
• If left eye, provided with a green filter, fixates
a green spot and right eye is provided with a
red filter, a projected red light will be seen
every where by the right eye except in the
region of the scotomas.

41. Filter Bar Method
• Patient fixates a spot of light
• A filter bar (palest filter) is
placed before the non-
suppressing eye
• the density of the filter is
increased until two lights are
seen
• This filter is a measure of
depth
Fig: Red filter bar

42. After-Image method (Hering-
Beilschowsky test)
• In clinical practice the test is performed by
using a battery-powered camera flash to
produce a vertical afterimage in one eye and
a horizontal afterimage in the other eye
• Resulting afterimage is that of a line with a
break in its middle, which represents the
fovea

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Hering-Beilschowsky After Image Test

44. • The patient fixates steadily the central mark,
first with one eye while the slit is horizontal
and then with the other eye while the slit is
vertical
• In a darkened room or with the eyes closed,
the patient sees the two successively
imprinted as positive afterimages (bright
lines)
• In a lighted room or with the eyes open,
negative afterimages (dark lines) will be seen

45. • Then open eyes and look at a plain surface and
see if lines cross
• In NRC the after images will coincide
• In ARC the after images will be separated

47. 4. Red Filter/Diplopia Method
• A spotlight is taken into account with both
eyes open
• A red filter before the strabismic eye and a
vertical prism (6-15∆) before one eye to move
the image out of the suppression area

48. • The patient should see one red and one white
light
• If vertically aligned but a strabismus is present
= HRC
• If separated, either NRC or UNRC

50. 5. Foveo-Foveal Test of Cu¨ppers
• An asterisk is placed on the fovea of the
deviated eye while the other eye fixates the
light on a Maddox cross or tangent screen
• If the fixation target appears to be
superimposed on the central fixation light of
the Maddox cross → normal retinal
correspondence

51. • In the presence of anomalous
correspondence foveae have different visual
directions
– The asterisk will be superimposed on one of the
numbers on the horizontal bar of the Maddox
scale
– This number indicates the angle of anomaly in
degrees

52. A,Schematic representation of the testing arrangement. B,Patient sees the asterisk
superimposed on the central fixation light of the Maddox scale(NRC, normal retinal
correspondence). C, The asterisk appears over the number 4 on the horizontal bar of the Madd
scale

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Visuoscopy
Test of eccentric fixation
Available in ophthalmoscope

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55. Tests for stereopsis
1. Titmus stereotest
• is a vectograph and
uses Polaroid
dissociation glasses

56. 2. TNO random dots stereotest
• An anaglyph, dissociation
is by color instead of
Polaroid filters

57. • TNO Random Dot Test:
– consists of seven plates,
each of which contains various shapes
Tests For Stereopsis:…

58. 3. Lang Stereotest
• Consists of card, approx.
the size of a average
post card in which
random dots are
incorporated in
paragraph
• Cylindrical lenses
laminated onto the
surface of the card are
used for dissociation of
the eyes

59.  Lang test