squint or strabismus evaluation

1. Dr.M.Sudheer Kumar

2.  Strabismus is misalignment of eyes.
 GOALS OF STRABISMUS EVALUATION
• To find the etiology of strabismus
• To assess the binocular status
• To measure the amount of deviation
• To diagnose amblyopia,
• To define a plan of management.


3.  A strabismus patient may be examined in the
following order:
• Eliciting a detailed history
• Visual acuity assessment
• Cycloplegic refraction
• Fundus examination
• Sensory tests
• Measurement of deviation
• Ocular motility examination
• Special tests for specific diagnosis

4.  requires special types of equipments


5. HISTORY
 Presenting complaints should be recorded in the
patient’s words.
 The age of onset and duration of squint is very
important for the prognosis regarding attainment and
maintenance of binocular single vision.
 Whether the deviation is intermittent or constant,
unilateral or alternating has to be asked
 History of treatment taken in the past like spectacles,
patching, previous surgery (for strabismus ,glaucoma
implant, retinal detachment, etc) should be noted.

6.  Family history should be taken for presence of
hereditary forms of strabismus.
 history of significant head posture, confirmed by old
photographs, may indicate good binocular potential.
 Antenatal and perinatal history is important for any
squint appearing since birth.
 A patient with recent onset of squint may present with
diplopia, past-pointing, abnormal eye movements and
headache.

7. EXAMINATION
 General Inspection of the Patient
Observation of the degree and direction of squint.
– Presence of wide nasal bridge with increased
interpupillary distance and epicanthal folds which may
be the cause of pseudoesotropia, needs to be noted.
– Observation of facial asymmetry.
– Presence of an abnormal head posture is noted

8.  Upward or downward slanting of palpebral fissures.
– Ptosis.
– Any lid/conjunctival scarring.
– Pupillary reactions are abnormal in patients with
sensory deviation due to diseases of retina and the
optic nerve
 Assessment of Visual Acuity : In children above 5 years
various Snellen’s charts can be used
Media and fundus examination:
 It is important to evaluate the eye for any organic
abnormality that could be causing visual loss and
secondary or sensory strabismus.

9.  It is the starting point for evaluation for strabismus.
 A refractive error could be the primary or a
contributing cause of the strabismus.
 Correction of the refractive error is paramount to the
management of strabismus.
 It is performed at the end of strabismus examination
and preferably under full cycloplegia for children.

13.  Assessment of Vision in Nystagmus
near acuity targets visible with binocular
viewing must be ascertained Before assessing
monocular vision in nystagmus patients
 When assessing monocular vision, an occluder
placed in front of one eye worsens the nystagmus
and leads to a decline in visual acuity.
 This decline can be avoided by high plus lenses by
fogging or neutral density filters

14.  Examination of squint can be considered in two
aspects:
a. Examination of sensory status
b. Examination of motor status

15.  Sensory testing is an essential part of strabismus
evaluation. It comprises the assessment of the binocular
status of the eyes
 different sensory adaptations that can take place in
response to clinical situations that disrupt binocular vision
are
 1. Visually mature (occurring after the visual system is
mature)
2. Visually immature (occurring during visual development
)


16.  Visually Mature:sensory adaptations occur after the
development of bifoveal fusion, when the visual
system is mature.
 These are associated with normal retinal
correspondence.
 Visual neural development is said to mature by
around 9 to 10 years of age.
 at this point there is not enough cortical plasticity
for adaptations such as cortical suppression and ARC

17.  Diplopia: The patients with diplopia fixate with one
fovea, and suppress the fovea of the deviated eye.
 The diplopic images come from the perifoveal retina of
the deviated eye.
 The foveal image from the fixing eye is perceived as
being located directly in front of the patient.
 while the perifoveal retinal image from the deviated
eye projects to its corresponding visual field.


18.  Exotropia causes the image to fall temporal to the
fovea, which projects to the nasal field producing
“crossed diplopia”
 Esotropia causes the image to fall on the nasal retina,
which projects temporally and causes “uncrossed
diplopia “


19.  Confusion: Instead of diplopia, strabismic patients
with confusion perceive two different images
superimposed on top of each other.
 Confusion is caused by the simultaneous perception of
two different images from the two foveae that are
pointing to different objects
 It is rarely seen clinically.

20.  Rivalry: is a condition where a patient with normal
binocular vision is presented with different images to
corresponding retinal points of each eye.
 Instead of seeing two different images superimposed
on each other (confusion)
 the subject perceives patchy dropout of each image
where the images binocularly overlap

22.  The following sensory adaptations occur when the
binocularity is disrupted during the first few years of
life, usually before 8 to 10 years of age.
 Monofixation and suppression: Small angle
strabismus (<10 PD), or mild to moderate unilateral
retinal image blur, in young children and infants
causes
- a central suppression scotoma of the deviated or
blurred eye,
- central fixation of the preferred eye,
- but peripheral fusion is maintained

23.  It refers to the ability of the sensory system to
appreciate the perceived direction of the fovea and
other retinal elements in each eye relative to the other.
 The two eyes have corresponding retinal elements that
have a common visual direction
 The two foveae represent the highest degree of
correspondence
 Abnormal retinal correspondence (ARC) is a
sensory adaptation of the immature sensory visual
system to an abnormal motor position of the eye.

24.  Worth’s Four Dot Test: The patient wears a red glass
in front of right eye and a green glass in front of left
eye.
 He then views a box with four lights; one red, two
green and one white

25.  If all four lights are seen, normal fusion is present.
• If all four lights are seen in the presence of a manifest
deviation, ARC is present.
• If two red lights are seen, left suppression is present.
• If three green lights are seen, right suppression is
present.
• If two red and three green lights are seen, diplopia is
present.
• If the red and green lights alternate, alternating
suppression
is present.

27.  Bagolini’s Striated Glasses: Each lens is covered
with fine striations which convert a point source of
light into a line, similar to the Maddox rod.
 The two lenses are placed at 45 degrees and 135
degrees in front of each eye and the patient fixates a
punctate light source placed at 6 meter away.


29.  This is the least dissociative of all diplopia tests.
It permits determination of whether the patient is:
• Fusing
• Suppressing one eye
• Suppressing centrally only
• The type of retinal correspondence present.

30.  After Image Test: This test demonstrates the visual
direction of the fovea.
 One fovea is stimulated by a vertical bright flash
of light and the fellow eye is stimulated by a horizontal
flash of light.
 The vertical flash of light is harder to suppress and
should be applied to the deviating eye.
 The patient then draws the relative positions of the
after images.

31.  Synoptophore: This is an instrument for
- assessing strabismus,
-Quantifying binocular single vision (BSV)
-Detects ARC and suppression

32.  Grades of binocular vision: Binocular vision is graded
on the basis of Synoptophore.
 First grade–(simultaneous macular perception) is
tested by introducing two dissimilar but not mutually
antagonistic pictures.
 one picture is smaller than the other so that the
smaller picture is seen by the fovea of one eye and the
larger picture is seen by the parafoveal area of the
other eye.

33.  Second grade–(fusion) is the ability of the two eyes to
produce a composite picture from two similar pictures
each of which is incomplete in one small different
detail.
 Third grade–(stereopsis) is the ability to obtain an
impression of depth by the superimposition of two
pictures of the same object which has been taken from
slightly different angles …

35.  These tests use one fixation target that is seen by both
eyes. Here we disrupt fusion by obscuring or
eliminating peripheral fusion clues, or providing
different images to each eye .
.Diplopia charting test
• Maddox rod (Most dissociating)
• Worth four dot test
• Red filter test
• Bagolini’s lenses (least dissociating)

36.  Diplopia test: Plotting of diplopia fields is indicated in patients
complaining of confusion or double vision.
 The patient is asked to wear red-green charting goggles; red in
front of the right eye and green in front of the left eye.
 The patient is made to sit with his head straight in a semi dark
room and is shown a fine linear light from a distance of 4 feet.
 The light is moved from primary position into all of other eight
directions of gaze.
 For each direction, the patient is asked to comment on the
position, brightness, separation between the red and green
images and the relative angle of one image to the other.

39.  The Maddox rod consists of a series of parallel glass
cylinders of higher power (usually red color) set
together in a metallic disk.
 The Maddox rod produces a linear image of a point light,
when viewed through the rod the line image is formed
perpendicular to the axis of the cylinders.
 The rod is placed in front of the right eye. This dissociates
the two eyes because the red streak seen by the right eye
cannot be fused with the unaltered white light seen with
the left eye.
 does not differentiate between tropia and phoria.


41.  Maddox Wing Test: Maddox wing is an instrument by
which the amount of heterophoria for near (1/3rd m)
can be measured subjectively.
 The instrument is constructed in such a way that the
right eye sees only a white vertical arrow and a red
horizontal arrow,
 whereas the left eye sees the horizontal and vertical
rows of numbers only

43.  The horizontal deviation is measured by asking the
patient towards which number the white arrow points.
 The vertical deviation is measured by asking the
patients regarding the number the red arrow
intersects.
 The amount of cyclophoria is measured by asking the
patient to move the red arrow so that it is parallel with
the horizontal row of numbers.

44.  It utilizes the principle of Hering’s law of equal
innervation.
 The test is performed with each eye fixating in turn.
The patient wears the red and green dissociating
glasses with the red glass over right eye.
 sits at 50 cm from an illuminated screen on which
each red target can be lit up in turn and its position
indicated by the patient using a linear green light.
 In orthophoria, the two lights are more or less
superimposed in all nine positions of gaze. The
relative positions are connected with straight lines.


46.  Lee’s Screen: The apparatus consists of two opalescent
glass screens at right angles to each other, bisected by a
two sided plane mirror which dissociates the two eyes.


47.  Interpretation of Hess/Lee's Screen Test
• The two charts are compared.
• The smaller chart indicates the eye with the paretic
muscle.
• The larger chart indicates the eye with the overacting
muscle.
• The smaller chart shows its greatest restriction in the
main direction of action of the paretic muscle.
• The larger chart will shows its expansion in the main
direction of action of the yoke muscle.

49. The examination of motor status includes:
1)Head posture
2)Measurement of ocular deviation
3)Limitation of ocular movements
4)Fusional vergences

50.  Head posture has three components:
a. Chin elevation or depression (vertical)
b. Face turn to the right or left side (horizontal)
c. Head tilt to the right or left shoulder (torsional).
 These three components at three different joints
between the head and the neck correct for the motility
disturbances in the three dimensions
 The patient chooses the head posture
where the ocular deviation is least, the ocular
alignment is maximum and where the images can be
fused.

52.  Light Reflex Tests
Hirschberg test:A pen torch is shone into the eyes from
arm’s length and the patient is asked to fixate upon the
light.
 If the eyes are deviated, the light reflex falls on
different locations instead of the center.
 1 mm deviation = 7 degrees deviation =14 pd deviation


54.  Krimsky test: It is a modification of the Hirschberg
test.
 A prism is placed in front of one eye with the apex
towards the deviation, a pen light is then thrown into
both eyes and the patient is asked to fixate on the
accommodative target.
 The prism is then increased or decreased until
the reflex becomes symmetrically centered in the
pupil.


55.  Bruckner test: This test is performed by using the
direct ophthalmoscope to obtain a red reflex from
both eyes simultaneously.
 In patients with strabismus, the test shows asymmetric
reflexes with the brighter reflex coming from the
deviated eye.


56.  based on the patient’s ability to fixate,
 both eyes should have central fixation.
 They allow the examiner to differentiate tropia from
phoria,
 Assess the degree of control of deviation, and note
fixation preference and strength of fixation of each
eye.

57.  Gold standard objective method
 Use: to differentiate
-between phoria and trophia
-detect pseudostrabismus
-differentiate concomitant from incomitant squint
done for both near (33cm) and distance (6 meter)
 Consist of 3 parts
1)cover test -confirms tropia
2)uncover test – to diagnose phoria
3)alternate cover test –measure total deviation

58. Ask pt tofixate on target and look for any deviation
Deviation visible ,eg:LE exo
Do COVER TEST,By
covering fixing eye,i.e RE
with occluder
Deviated LE
moves inward
to take
fixation,so RE
under occluder
also moves due
to herrings law.
CONFIRMS
EXOTROPHIA
No movement,
Indicate
pseudosquint
Deviation not visible
Do COVER TEST
If no movement of
uncovered eye no tropia
But fusion is broken ,so covered eye moves
to position of least resistance.now do
UNCOVER TEST

59.  On uncovering ,the covered eye is seen to move inward
 Indicate PHORIA

61.  This test is done to dissociate binocular fusion
in order to determine the full deviation, including any
latent phoria.
 Alternately each eye is occluded and refixation
movement of uncovered eye to midline is observed.
 No shift in the alternate cover test indicates
orthophoria.
 A refixation shift to indicates that strabismus is
present, either a tropia, phoria.

62.  This test determines the amount of prism necessary to
neutralize the full deviation including any latent
phoria, by quantitating the shift associated with
alternate cover testing.
 A prism is placed in front of the deviating eye
with the apex towards the deviation.
 Alternate cover testing is then performed with the
prism in place, the prism is changed (either increased
or decreased) depending on the refixation shift.

63.  Simultaneous prism cover test: It is used to measure
the tropia component of the monofixation syndrome
without dissociating the phoria.
 therefore it is used in patients with small angle
strabismus.
 A prism and occluder is presented
simultaneously in front of either eye
and this process is repeated until
there is no shift of the deviated eye
when the fixing eye is covered

64.  When measuring patients with restrictive or paralytic
deviations the primary and secondary deviation should be
considered.
 In accordance with Hering’s law, the deviation is larger
when the eye with limited duction is fixing (secondary
deviation) than when the “good eye” fixes (primary
deviation).
 While measuring a deviation with prisms, the eye without
the prism is considered the fixing eye and the eye with the
prism is the non-fixing eye, irrespective of presence of
amblyopia.
 This is because the eye without the prism must come to the
primary position to take up fixation.

65.  Ductions : Mono ocular movements and are examined
with one eye occluded,
-abduction -adduction
-elevation -depression
-intortion -extortion
 Versions : are binocular ,simultatneous eye
movements In the same direction ,i.e conjugate
movements
-Dextroversion -Levoversion
-Dextro elevation -Levoelevation
-Dextrodepression -Levodepression
-Sursumduction -Deorsumduction

66.  Both horizontal and vertical ductions are quantified with
a graded 0 to minus 4 scale,
 with minus one limitation meaning slight limitation and
minus four limitation meaning severe limitation
 Evaluation of versions include eye movements through
all 9 cardinal gaze positions. Abnormal versions can be
noted on a scale of + 4 through 0 to – 4, with 0 indicating
normal movement,
 + 4 indicating maximum overaction, while – 4 indicates
severe underaction.
 The rest of the grades fall in between.

68. - Binocular , simultaneous movements in opp direction
- i.e disgugate movements
-Vergence amplitudes are tested in three planes:
1. Horizontal: Convergence and divergence
2. Vertical: Sursumvergence and deosumvergence
3. Torsional:Incyclovergence and excyclovergence.
- Measurement can either be done with prisms or the
synoptophore

69.  Near point of convergence: The simplest way to
measure convergence is to bring a point drawn on
paper closer to the eyes, till the point becomes double.
 This in the near point of convergence. The point at
which it becomes blurred is the near point of
accommodation
 Normally, the near point of convergence is 8 to 10 cm.

70.  Convergence and divergence for near (33 cm) and
distance (6 m) can be measured with the help of a
prism bar or rotary prisms.
 Using base-out prisms, the convergence
amplitudes can be measured
 using base-in prisms, the divergence amplitudes are
measured.

71. Thank you