eye

1. STRABISMUS

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

3. 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
• 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

8. • 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 .

9. • 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.
Versions
– Versions are binocular, simultaneous, conjugate movements ( in the same
directon ) .
– Dextroversion and laevoversion elevation and depression .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.

11. • 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

13. • 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 .

15. 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

18. 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

19. Diagnosis
• 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

20. treatment
• 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

21. EXAMINATION

22. EXAMINATION
History:
A careful history is important in the diagnosis of
strabismus
A. Family History
B. Age at Onset
C. Type of Onset
D. Type of Deviation
E. Fixation

23. EXAMINATION
• Visual Acuity
• Determination of Refractive Error
• Inspection

27. EXAMINATION
• Determination of Angle of Deviation (Angle of
Deviation)
a. Prism and Cover Tests
1. Cover tests
2. Uncover tests
3. Alternate cover tests
4. Prism plus cover testing
b. Objective tests
1. Hirschberg method
2. Prism reflex method (Krimsky test)

29. EXAMINATION
• Ductions (Monocular Rotations)
• Versions (Conjugate Ocular Movements)
• Disjunctive Movements
– Convergence
– Divergence

32. EXAMINATION
• Sensory Examination
– Stereopsis testing
– Suppression testing

36. Classification of Esotropia
• 1. Accommodative
– a Refractive
Fully accommodative
Partially accommodative
– b Non-refractive
With convergence excess
With accommodation weakness
– c Mixed

37. 2.Non- accommodative
– Essential infantile
– Microtropia
– Basic
– Convergence
– Convergence spasm
– Divergecne insufficiency
– Divergecne Paralysis
– Sensory
– Consecutive
– Acute onset
– Cyclic

38. • Classification of Exotropia
Constant (early onset ) exotropia
Intermittent exotropia
Sensory exotropia
Consecutive exotropia

41. Objective and Principles of Therapy
of Strabismus

42. 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

43. Objective and Principles of Therapy of
Strabismus
• Timing of treatment on children

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

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