assessment of strabismus by Dr. ANWESHA MANNA, OPHTHALMOLOGY

2. INTRODUCTION:
DEFINITION:
Strabismus is the
condition when
visual axis of two
eyes do not meet at
the point of fixation.

3.  COMITANT: Although misaligned they retain relation in
all direction of gaze
 INCOMITANT: Deviation is different in all position of gaze
 TROPIA: It is manifest ocular misalignment .
 PHORIA: It is latent ocular deviation.
 ALTERNATE : Fixation is retained by alternate eye
 UNILATERAL: Only one eye habitually fixes
 INTERMITTENT: when deviation remain only for some
time

4. Contd..
Tropia Or Phoria can
be,
 Esotropia /phoria
 Exotropia/phoria
 Hypertropia/phoria
 Hypotropia/phoria
 Cyclotropia/phoria

5. ASSESSMENT:
History
Visual Acuity
Examination:
1) Examination of motor status : a) Head posture
b) Ocular deviation
c) Ocular motility
d) Diplopia
2) Examination of sensory status & adaptation
 Refraction & fundoscopy

6. HISTORY

7.  The age of onset
 Gradual or sudden (old photographs may sometime
help)
 Symptoms, i.e. diplopia/ discomfort/ blurring/ eye
ache/ cosmetic
 Whether the symptoms occur during fatigue / illness/
stress/inattentive condition etc.
 Whether it occurs for near/ distant vision
 Whether it is unilateral/ alternate or constant/
intermittent.
 General health ( measles, whooping cough), birth
history( LBW) & family history( high refractive error,
strabismus)
 Previous treatment if any, & type & improvement after
it.

8. VISUAL ACUITY

9. TESTING IN < 1YR AGE:
 OKN test
 Catford drum test
 Preferential looking
test
 Teller acuity card test
 Visually evoked
potential
 Indirectly by, blinking &
fixation( central, steady
, maintained)

10. TESTING IN 1-3 YRS AGE:
 Cardiff acuity card test
 Marble game test
 STYCAR graded balls
vision test
 Coin test, Miniature toy
test, etc.

11. TESTING 3-5 YRS AGE:
 Lea symbol chart
 Broken wheel acuity
 Sheridan- gardiner test
 Tumbling E test
 TESTING IN PRE-
SCHOOLAGE:
 Can be done by
snellen’s chart/ above
tests

12. EXAMINATION OF MOTOR STATUS:
 ABNORMAL HEAD POSTURE (AHP) :
 Chin elevation/ depression (vertical).
 Face turn to right/ left side ( horizontal).
 Head tilt to right or left shoulder (torsional).
 CAUSES:
Incomitant squints
A –V phenomenon
One eyed persons

13. OCULAR DEVIATION:
 Is it a true squint/ pseudo
or apparent squint?
 Causes of pseudo
strabismus:
Telecanthus
Epicanthus
Hypertelorism
Ptosis
Lid retraction
Large angle κ

14. ANGLE KAPPA:
 It is the angle subtended by the visual and
optical axis and is usually about 5° (positive).

15. Contd…
A large positive angle
κ stimulate exotropia
as in high hyperopia
 A negative one
stimulate esotropia
as in high myopia

16. TESTS TO MEASURE & DETECT
OCULAR DEVIATION:
1) Cover test
2) Cover- uncover test
3) Alternate cover test
4) Prism bar cover test
5) Maddox rod test
6) Double maddox rod test
7) Maddox wing test
8) Hirschberg’s test
9) Krimsky test
10) Bruckner test
11) 4D prism test
corneal reflection test

17. COVER TEST:
Fixation of eyes
Cover the apparently fixating eye
Observe the deviation of the other eye
Movement confirms manifest or true
squint(Heterotropia)

19. COVER-UNCOVER TEST:
One of the eyes is covered 2-3 sec
Then cover removed
In heterophoria the eye behind cover deviates
Examiner observes the movement of the on
removal of cover

21. ALTERNATE COVER TEST:
The right eye covered for several seconds
Occluder quickly shifted to the opposite eye for 2sec
It repeats for several times
Examiner notes the recovery of eye position
Compensated heterophoria will have straight eyes,
but poor control patient may show manifest
deviation

22. PRISM BAR COVER TEST:
Prism of increasing strength is placed in
front of squinting eye
Cover & alternate cover test is performed
Until the movement stops

24. MADDOX ROD TEST:
 ORTHOPHORIA
: streak passes
through white
light.
 If streak passes
on the left to
the light i.e.
esophoria &, if
to the right then
exophoria

25. DOUBLE MADDOX ROD TEST:
A red maddox rod is put in
front of suspected eye & white
in front of other eye.
Now a 6D prism is put
behind white rod
The rods are kept at 90° in
trial frame

26. Result:
 Orthophoria: 2 line
will be parallel
 Cyclodeviation : Not
parallel, red line will be
inclined.
 Angle can be
measured by rotating
the rod

27. MADDOX DOUBLE PRISM:
 Patient will see 3 horizontal line parallel to
each other.
 In cyclodeviation Intermediate line will be
oblique.

28. MADDOX WING TEST:
R/E : white arrow
vertically And red
arrow horizontally
pointing left.
L/E :Horizontal row of
figures in white and
Vertical row in red

29. Contd…
 White arrow measures
horizontal tropia
 Red arrow measures
vertical tropia
 In cyclophoria red
scale is adjusted to
appear parallel to
horizontal scale.

30. HIRSCHBERG TEST:
 Corneal reflections
are usually symetrical
in absence of squint
 In esodeviation
reflex fall on
temporal cornea.
 Roughly 1mm shift
signifies 7° or 15
prism diopter.

31. KRIMSKY TEST:
A prism bar is placed in
font of the fixating eye
The power increased
until the reflections get
symmetrical.

32. BRUCKNER TEST:
 Direct ophthalmoscope
is used to obtain a red
reflex simultaneously in
both eyes.
 In strabismus , the
deviated eye will have a
lighter and brighter
reflex.

33. 4 D PRISM TEST:
BIFOVEAL FIXATION:
 Base-out prism
placed in front R/E
 For fixation B/E
move to left
 Then L/E moveTo
right side to fuse
image

34. IN LEFT MICROTROPIA:
 When prism placed
in front L/E no
movement of
either eye is seen
 When moved to
R/E , R/E adducts,
Also the L/E
Abducts
 But L/E do not
Adducts again to
fuse image

35. OCULAR MOVEMENTS:
 Ductions: Monocular movement
 Versions: Binocular , simultaneous conjugate
movement.
 Vergences: Binocular, simultaneous,
disjugate movement .

36. ACTION OF EXTRA-OCULAR MUSCLES:

37. 9 POSITION OF GAZE:

38.  Near point of
convergence:
Nearest point on which eye
can maintain binocular
fixation.
Measured by RAF rule
It should be Less than 10 cm.
 Near point of
accommodation:
Nearest point on which eyes
can maintain clear focus.

39. CONVERGENCE TEST:
Hold a pencil / a finger at distance of 30-40cm
Ask the patient to look
at its tip
Bring it nearer to
patient’s eyes.
kept at the eye level of patient till the eye develops
Diplopia or one eye Deviates

40. FUSIONAL AMPLITUDE:
It is the efficacy of vergence movements.
 It is done by increasing prism dioptre.
 Vertical fusional reserve: 1.5°-2.5°
 Horizontal negative fusional reserve
(abduction range): 3°-5°
 Horizontal positive fusional reserve
(adduction range) : 20°-40°

41. PRISM VERGENCE TEST:
Patient at 6m distance from light source
The highest Prism that permits single
vision gives
Verging Power

42. TESTS FOR DIPLOPIA:
 Diplopia charting
 Hess screen test
 Lees screen test
 PARK’S 3 step test
 Forced duction test

43. DIPLOPIA CHARTING:
 Maximum separation is in the quadrant in
which the muscle acts most
 The level of 2 image
 In which direction the image is deviated
(image displaced toward the direction of
action of the muscle)

44. LEFT LATERAL RECTUS PALSY:

45. HESS CHART:
 Patient is asked to
superimpose green light
on the red light.
 Procedure repeated with
red filter in front of left
eye.
 The points are marked by
examiner.
RESULT:
 In orthophoria: both
lights superimpose in 9
position of gaze.

46. Rt 6th nerve
palsy:

47. R/E 4th nerve palsy:

48. LESS SCREEN:
 Consists of two
opalescent glass
screens at right-
angles to each other,
bisected by a two-
sided plane mirror
which dissociates the
two eyes
 interpretation done
as like hess chart

49. PARK’S 3 step test:
 Use to identify cyclovertical muscle paralysis.
 Performed by measuring the vertical
alignment in
1)primary position,
2) In right and left gaze and
3) In head tilt to the right and to the left.

50. RIGHT HYPERTROPIA:
1) Circle the muscles which pull R/E down or L/E
up

51. 2) Determine whether vertical deviation is more
on left/ right gaze

52. 3) If worse when head tilted to right, tilt the
circles to the right

53. FORCED DUCTION TEST:
Anesthetize the eye
Lids retracted
Patient looks in the direction of
the muscle tested
Globe hold at the opposite limbus
with globe holding forceps
Eye is rotated at the direction of
action of muscle

54. Contd..
RESULT:
 If free movement is
present then the test
is negative
 If restricted then the
test is positive

55. EXAMINATION OF SENSORY STATUS:
 Binocular vision & its grade
 Type of Retinal correspondence
 Suppression
It Determines prognosis in a case of squint.

56. GRADES OF BINOCULAR VISION:
1) First grade
(simultaneous
perception):
2) Second grade
(Fusion):
3) Third grade
(stereopsis)

57. SUPPRESSION:
 It is active inhibition of image of one eye by the
visual cortex, when both eyes are open.
 Stimuli :
 Diplopia
 Confusion
of image
 Blurred
image

58. RETINAL COREPONDENCE:
Each retina share the
same subjective visual
direction i.e.
In primary position:
both fovea
In right sided object:
Right nasal & left
Temporal retina , & vice
versa.

59. Abnormal retinal
correspondence:
Abnormal retinal
correspondence is a
condition in which non-
corresponding retinal
elements acquire common
subjective visual direction.

60. TESTS FOR SENSORY STATUS:
1) Bagolini’s striated glass test
2) Worth four dot test
3) After-image test
4) Synoptophore

61. BAGOLINI STRIATED GLASS TEST:
Symmetrical cross
response
Asymmetrical cross
response
Single line present
 Cross response with
gap in one line

62. WORTH FOUR DOT TEST:
 All 4 lights seen –
NRC/ Harmonious
ARC
 Left suppression – 2
red light
 Right suppression – 3
green light
 Diplopia – 3 green &
2 red light
 Alternating
suppression –
Alternate green & red
light.

63. AFTER-IMAGE TEST(HERING-
BIELSCHOWSKY ):
A bright linear light is used
Patient views the target with one eye and the
light is flashed
For R/E flash held vertically & for L/E horizontally
Patient appreciate a plus sign.

64. Contd…
a) is consistent with normal retinal correspondence
(NRC), (b) shows uncrossed after-image(diplopia)
and anomalous retinal correspondence (ARC) and
(c) shows left supression

65. SYNOPTOPHORE:
 It is an instrument ,used for potential for
binocular function in presence of manifest
squint, & tests SP, FUSION, STEREOPSIS

66. TESTS FOR STEREOPSIS:
1) TNOTEST
2) FRISBYTEST
3) LANGTEST
4) TITMUSTEST

67. TNO RANDOM DOT TEST:
Consists of seven plates of
randomly distributed
paired red-green dots.
Test targets are only
visible to individuals who
have stereopsis .

68. FRISBY TEST:
 Consists of 3
transparent plates of,
each printed with 4
squares.
 1 of the squares
contains a hidden
circle, & the random
shapes are printed on
the reverse side.
 Patient needs to find
out the hidden circle.

69. LANG TEST:
 Here glass is not used.
Patient has to identify simple shape (star ) on
the card

70. TITMUS TEST:
Viewed through
polaroid spectacle
 Right plate contains
a picture of fly
 Left contains 9
squares, each
containing 4 circles,
of which 1 has
disparity
 test done at 40cm
distance

71. Contd…
FLY: Appears to stand
out from page
CIRCLES: 1 circle form
disparity & appear
forward.
THE ANIMALS : 3 rows
of animal ,one of
which appear forward.

72. Fundoscopy & refraction:
 Dilated fundoscopy is mandatory.
 To exclude any underlying ocular pathology
such as macular scarring, optic disc hypoplasia
or retinoblastoma.
 Proper Refractive correction should be given
by retinoscopy

73. CONCLUSION
It is a common childhood & adult problem.
It is extremely difficult to examine a child and
a tactful examination is to be done.
Quantification of the angle of deviation,
binocular vision, ocular movement, refraction is
important for diagnosis & proper treatment
purpose.