Squint basics Fourth year lecture Poonch Medical College Rawalakot AJK Pakistan

MBBS ophthalmology lecture on basics of squint

1. STRABISMUS
Prof Munim
PMCR

2. •Strabismus ; misalignment of the visual axes
•orthophoria ; perfect alignment of the visual axes.
Most individuals have heterophoria
•Heterophoria ; (latent squint) tendency of the eyes
to deviate. Ocular alignment maintained with effort.
•Heterotropia; (manifest squint) which is present at
all times
Prof Munim

3. •Esophoria; latent squint inwards turning of the
eyes
•Esotropia; manifest squint inwards turning of the
eyes
•Exophoria; latent squint outwards turning of the
eyes
•Exotropia; manifest squint outwards turning of
the eyes
•Hyperphoria/hypertropia; latent/manifest squint
upwards turning of eyes
•Hypophoria/hypertropia; latent/manifest squint
downwards turning of eyes
Prof Munim

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7. •Anatomical axis ; is a line passing from the
posterior pole through the centre of the
cornea .
•Visual axis ; line of vision ; extending from the
point of fixation to the fovea
•Angle kappa is the angle subtended by the
visual and anatomical axes .
Prof Munim

8. •5.0°
•A positive angle kappa of 5.0° on average is generally found in the normal
human eye12. A normal nasal ward displacement of the corneal light
reflex from the center of the pupil is called a positive angle kappa. A
temporal ward displacement is negative.
Prof Munim

9. •Causes for Pseudostrabismus
•Pseudoesotropia: Prominent epicanthal fold and negative angle kappa
•Pseudoexotropia: Hypertelorism and positive angle kappa
•Causes for Heterophoria
•• Anatomical causes: Orbital asymmetry, abnormal interpupillary
distance (IPD), mild weakness of extraocular muscles, etc.
•• Physiological causes: Esophoria is seen in increased
accommodation (hyperopes) and exophoria in decreased accommodation
(myopes).
•• Decompensation causes illness, the inadequacy of the fusional
reserve, older age, and precision jobs
Prof Munim

10. •Causes of Concomitant Squint:
•Sensory causes: These interfere with a clear image formation in one eye.
Refractive errors, anisometropia, media opacities, obstruction of pupillary
area, macular and optic nerve diseases
•The motor causes: These interfere with ocular alignment. Orbital,
extraocular muscle, and accommodation abnormalities.
Prof Munim

11. Extraocular muscles
•Horizontal muscles;
–Medial rectus-; Its sole action in the primary position is adduction.
occulomotor nerve supply
–Lateral rectus- Its sole action in the primary position is abduction.;
abducens nerve supply
•Vertical muscles;
–Superior rectus- Primary action elevation (secondary actions are
adduction and intorsion. Oculomotor r nerve supply
–Inferior rectus ; The primary action is depression ; secondary actions
are adduction and extortion. oculomotor nerve supply
Prof Munim

12. •Oblique muscles;
–Superior oblque; Originates superomedial to the optic foramen. It
passes forwards through the trochlea at the angle between the
srperior and medial walls and is then reflected backwards and laterally
to insert in the posterior upper temporal quadrant of the globe.The
primary action is intorsion ;secondary actions are depression and
abduction. oculomotor nerve supply
–Inferior oblique; Orginates from a small depression just behind the
orbital rim lateral to the lacrimal sac. It passes backwards and
laterally. To insert in the posterior lower temporal quadrant of the
globe, close to the macula. The prmary action is extorsion;;secondary
action are elevation and abduction . oculomotor nerve supply
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17. •Listing plane is an imaginary coronal plane passing through
the centre of rotation of the globe. The globe rotates on the
X,Y and Z axes of Fick., which intersect in Listing plane .
•The globe rotates left and right on the vertical Z axis.
•The globe moves up and down on the horizontal X axis.
•Torsional movements (wheel rotations) occur on the Y
(sagittal ) axis which traverses the globe form front to back
(similar to the anatomical axis of the eye )
•Intorsion occurs when the superior limbus rotates nasally and
extorsion on temporal rotation .
Prof Munim

18. •OCULAR MOVEMENTS
•Ductions
–Ductions are monocular movements around the axes of Fick. They
consist of
–adduction,abduction elevation, depression, intosion and extorrsion .
–They are tested by occluding the fellow eye and asking the patient to
follow a target in each direction of gaze.
Prof Munim

19. Versions
–Versions are binocular, simultaneous, conjugate movements
( in the same directon ) .
–Dextroversion and laevoversion sursumversion and deorsumversion .
–These four movements bring the globe into the secondary positions
of gaze by rotation around either a vertical or a horizontal X axis of Fick.
–Dextroelevation and dextrodepression and laevoelevation and
laevodepression . These four oblique movements bring the eyes into the
tertairy positions of gaze by rotation around oblique axes in listing
plane, equivalent to simultaneous movement about both the horizontal
and vertical axes.
–Torsional movements which maintain upright images occur on tilting of
the head.
Prof Munim

20. •VERGENCES
•Vergences are binocular, simultaneous disjugate or
disjunctive movements .Convergence is simultaneous
adduction; divergence is outwards movement from a
convergent position. Convergence may be voluntary or reflex.
Reflex convergence has four components:
–Tonic
–Proximal
–Fusional
–Accommodative
Prof Munim

21. •Positions of gaze
•Six Cardinal positions of gaze are those in which one
muscle in each eye has to move the eye into that
position as follows:
–Dextroversion
–Laevoversion
–Dextroelevation
–Laevoelevation
–Dextrodepression
–Laevodepression
Nine Diagnostic position of gaze are those in which
deviations are measured. They consists of the six cardinal
postions ,the primary position, elevation and depression .
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24. Laws of ocular motility
•Agonist ; antagonist – muscles of the same eye moving
the eye in opposite direction; medial and lateral rectus
•Synergists= muscles of the same eye moving it in the same
direction; superior rectus and inferior oblique causing
elevation
•Yoke muscles= muscles of both eyes moving the eyes in
same direction; medial rectus of both eyes
•Sherrington law; increase in innervation to one muscle
causes decreased innervation to its antagonist; medial and
lateral rectus
•Hering law; equal innervation flows to yoke muscles in eye
movement ; medial rectus of both eyes
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28. Consequences of squint
Suppression , amblyopia , confusion and diplopia , postural
changes according to strabismus
1. Amblyopia
–Definition – unilateral or bilateral decrease of best corrected visual
acuity caused by stimulus deprivation or abnormal interaction for
which there is no pathology of the eye or the visual pathway
–Types
•Strabismic amblyopia; abnormal interaction
•Stimulus deprivation amblyopia ; form vision deprivation
•Anisometropic amblyopia; difference of refractive errors in both eye ; one
eye is amblyopic
•Ametropic amblyopia; form vision deprivation of both eyes
•Meridional amblyopia; because of astigmatism
Prof Munim

29. •1. visual acuity; difference of two lines in best
corrected visual acuity in the absence of
organic lesion
•2. neutral density filter; normal eyes have
visual acuity reduced by two lines but there is
no change in amblyopia
Prof Munim

30. •Sensitive period during which the amblyopia
can be cured is below 10 years of age
•1. occlusion of the normal eye to encourage
the use of the abnormal eye is the most
effective treatment
•2. penalization; of the normal eye ; blurring of
the vision with atropine
Prof Munim

31. •How to Manage a case of Strabismus ?
Prof Munim

32. 1. History
2. Examination
3. Clinical Tests
4. Treatment

33. History:
A careful history is important in the diagnosis of strabismus
A.Family History
B.Age at Onset
C.Type of Onset
D.Variability
E.Type of Deviation
Prof Munim

34. EXAMINATION
Visual Acuity
Examination of Eye especially for media opacities, macular and
optic nerve disease
Ocular Movements
Measurement of Angle of Squint ( Motor Exam)
Bruckners Test
Hirschberg Test / Krimsky Test
Cover Test / Uncover Test / Alternate Cover Test / Prism Cover T
Sensory Examination (Amblyoscope)
Stereopsis testing (Titmus Fly )
Suppression Testing ( Worths Four Dot )
Determination of Refractive Error
Cycloplegic Refraction
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36. Determination of Angle of Deviation
(Angle of Deviation)
Bruckner’s test
Corneal Reflection test
1. Hirschberg method
2. Prism reflex method (Krimsky test)
Cover Tests
1. Cover tests
2. Uncover tests
3. Alternate cover tests
4. Prism plus cover testing
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39. 1 mm =
7 Degrees =
15 Prism Diopters
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41. • Observe corneal reflexes ( symmetrical / asymmetrical)
•If Asymmetrical DO COVER/UNCOVER TEST
–Cover the fixating eye COVER TEST
–Observer the deviated eye ( Movement / No movement)
–Movement means manifest squint in uncovered eye
–No movement means no squint / poor vision / eccentric fixation
–Observe the behavior of covered eye as it is uncovered ( movement / no
Movement) UNCOVER TEST
–Movement means manifest squint in opposite eye
–No movement means alternate Manifest squint
•If Symmetrical DO ALTERNTE COVER TEST
–Cover any eye alternatively for 2-3 seconds and note the behavior of covered
eye as it is uncovered ( movement / no movement)
–Movement means Latent Squint
–No movement means Orthophoria
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47. Classification of Esotropia
1. Accommodative
Refractive
Non-refractive
Mixed
2. Non-accommodative
Essential infantile
Convergence spasm
Divergence insufficiency /paralysis
Sensory
Consecutive
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49. Classification of Exotropia
1.Constant (early onset ) exotropia
2.Intermittent exotropia
3.Sensory exotropia
4.Consecutive exotropia
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54. Principles of Therapy of Strabismus

55. Objective and Principles of Therapy of
Strabismus
•Reversal of the deleterious sensory effects of
strabismus (amblyopia, suppression and loss
of stereoposis)
•Best possible alignment of the eyes by medical
or surgical treatment
Prof Munim

56. Objective and Principles of Therapy of
Strabismus
•Timing of treatment on children
Prof Munim

57. Medical Treatment
•Treatment of Amblyopia
–Occlusion therapy
•Initial stage
•Maintenance stage
–Atropine therapy
•Optical Devices
–Spectacles
–Prisms
•Botulinum Toxin
•Orthoptics
Prof Munim

58. Surgical Treatment
•Surgical procedures
–Resection and recession
–Shifting of point of muscle attachment
–Faden procedure
•Choice of muscles for surgery
•Adjustable sutures
Prof Munim