Ophthalmology lecture

1. Dr. Ahmed Halal
MD, Ophthalmologist
Halal Eye Specialist
Hospital
STRABISMUS

2. Contents
 OCULAR MOTILITY SYSTEM &
EXTRAOCULAR MUSCLES
 BINOCULAR SINGLE VISION
 AMBLYOPIA
 STRABISMUS DEFINITION AND
CLASSIFICATION
 CLINICAL EVALUATION
 MANAGEMENT
 DISCUSSION SESSIONS

3. OCULAR MOTILITY
SYSTEM

4. SYSTEM

5. The Eyes as a Sensorimotor
Unit
 Light stimuli
 Refractive media
 Retina
 Physicochemical and
electrical changes
 Visual Pathway
 Central nervous system
 Visual sensations of
form, spatial
relationships, and color
appear in our
consciousness.
 Transforming the field
of vision into the field
of fixation
 Bringing the image of
the object onto the
fovea
 Positioning the two
eyes in such a way
that they are properly
aligned at all times
 Ensuring the
maintenance of single
Sensory
Tasks
Motor
Tasks
This sequence of events may be called
the Sensory aspect of the visual
process
These events may be called the Motor
aspect of the visual process

6. EXTRAOCULAR MUSCLES
Origin, Insertion, Action, Nerve

7. Types of ocular movements
(A) Uniocular movements are
called ‘ductions’ and include
the following:
 1. Adduction. It is inward movement
(medial rotation) along the vertical
axis.
 2. Abduction. It is outward movement
(lateral rotation) along the vertical
axis.
 3. Supraduction. It is upward
movement (elevation) along the
horizontal axis.
 4. Infraduction. It is downward
movement (depression) along the
horizontal axis.
 5. Incycloduction (intorsion). It is a
rotatory movement along the
anteroposterior axis in which superior
pole of the cornea (12 O’clock point)
(B) Binocular movements.
These are of two types:
versions and vergences:
1. Versions, also known as
conjugate movements, are
simultaneous symmetric
movements
of both eyes in the same
direction. These include:
Dextroversion, Levoversion,
Supraversion, Infraversion,
Dextrocycloversion,
Levocycloversion.
2. Vergence, also called
disjugate movements, are
simultaneous and symmetric
movements of both eyes
in opposite directions e.g:
1. Convergence. It is
simultaneous inward
movement of both eyes
2. Divergence. It is

8. Diagnostic positions of gaze
 There are nine diagnostic positions of gaze.
 These include one primary, four secondary and
four tertiary positions.

10. BINOCULAR SINGLE
VISION

11. Definition
 When a normal individual fixes his visual attention
on an object of regard, the image is formed on
the fovea of both the eyes separately; but the
individual perceives a single image. This state is
called binocular single vision.

12. Visual development
 Binocular single vision is a conditioned reflex
which is not present since birth but is acquired
during first 6 months and is completed during first
few years the process of its development is
complex and partially understood.
 At birth there is no central fixation and the eyes
move randomly.
 By the first month of life fixation reflex starts
developing and becomes established by 6
months.
 By 6 months the macular stereopsis and
accommodation reflex is fully developed.

13. Grades of binocular single
vision
 Grade I — Simultaneous perception. It is the
power to see two dissimilar objects
simultaneously.

14. Grades of binocular single
vision
 Grade II—Fusion. It consists of the power to
superimpose two incomplete but similar images to
form one complete image.

15. Grades of binocular single
vision
 Grade III— Stereopsis. It consists of the ability
to
 perceive the third dimension (depth perception).

16. Single Binocular vision
requires three factors for its
development:
 1. Reasonable clear vision in both
eyes
 2. Coordination of both eyes (NRC)
 3. Ability of visual cortex to promote

17. Anomalies of binocular
vision
Confusion and Diplopia

18. Compensatory Mechanism of
double vision
 Suppression
 Amblyopia
 Abnormal retinal correspondence (ARC)
 Abnormal head posture
 Eye closure

19. Amblyopia is the unilateral, or rarely bilateral,
decrease in best corrected visual acuity (BCVA)
caused by vision deprivation and/or abnormal
binocular interaction, for which there is no
identifiable pathology of the eye or visual
pathway.
AMBLYOPIA

20. Classification
 Strabismic amblyopia: results from abnormal binocular interaction
where there is continued monocular suppression of the deviating eye.
 Anisometropic amblyopia: is caused by a difference in refractive
error between the eyes and may result from a difference of as little as 1
dioptre.
 Stimulus deprivation amblyopia: results from vision deprivation. It
may be unilateral or bilateral and is typically caused by opacities in the media
(e.g. cataract) or ptosis that covers the pupil.
 Bilateral ametropic amblyopia: results from high symmetrical
refractive errors.
 Meridional amblyopia: results from image blur in one meridian. It can be
unilateral or bilateral and is caused by uncorrected astigmatism (usually >1 D)
persisting beyond the period of emmetropization in early childhood.

21. MANAGEMENT
 Occlusion of the normal eye, to encourage use of the
amblyopic eye, is the most effective treatment.
 Penalization, in which vision in the normal eye is
blurred with atropine, is an alternative method.
(younger the child, better the prognosis)

22. Full-time vs part-time Occlusion?
Age and Outcome?
Density & Outcome?
Organic disease and amblyopia?
Poor compliance?
DISCUSSION SESSION

23. STRABISMUS

24. DEFINITION
 Normally visual axis of the two eyes are parallel
to each other in the ‘primary position of gaze’ and
this alignment is maintained in all positions of
gaze (Orthophoria).

25. Classifications

27. PSEUDOSTRABISMUS
 In pseudostrabismus (apparent squint), the
visual axes are in fact parallel, but the eyes seem
to have a squint:
 1. Pseudoesotropia or apparent convergent
squint may be associated with a prominent
epicanthal fold (which covers the normally visible
nasal aspect of the globe and gives a false
impression of esotropia).
 2. Pseudoexotropia or apparent divergent
squint may be associated with hypertelorism, a
condition of wide separation of the two eyes

30. HETEROPHORIA
 Heterophoria also known as ‘latent strabismus’, is
a condition in which the tendency of the eyes to
deviate is kept latent by fusion. Therefore, when
the influence of fusion is removed the visual axis
of one eye deviates away.

31. Types of heterophoria
 1. Esophoria:
 Convergence excess type (esophoria greater for near
than distance).
 Divergence weakness type (esophoria greater for
distance than near).
 Non-specific type
 2. Exophoria:
 Convergence weakness type (exophoria greater for near
than distance).
 Divergence excess type (exophoria greater on distant
fixation than the near).
 Non-specific type
 3. Hyperphoria & Hypophoria
 4. Cyclophoria (incyclophoria, excyclophoria)

32. Etiology
 1. Anatomical factors (Orbital asymmetry, Abnormal
interpupillary distance (IPD), A mild degree of extraocular
muscle weakness)
 2. Physiological factors:
 1. Age. Esophoria is more common in younger age group.
 2. Role of accommodation. Increased accommodation is
associated with esophoria (as seen in hypermetropes and
individuals doing excessive near work) and decreased
accommodation with exophoria (as seen in simple myopes).
 3. Role of convergence. Excessive use of convergence may
cause esophoria while decreased use of convergence is often
associated with exophoria
 4. Dissociation factor such as prolonged constantuse of one
eye may result in exophoria (as occurs in individuals using
uniocular microscope and watch makers using uniocular

33. Complaint
 Depending upon the symptoms heterophoria can be
divided into compensated and decompensated
 1. Compensated: It is associated with no subjective
symptoms.
 1. Decompensated:
 Pain (Asthenopia, Headache, Photophopia)
 Difficulty in changing the focus
 Blurring of vision
 crowding of words while reading
 Intermittent diplopia
 Poor depth perception

34. Examination
 Testing for vision and refractive error
 Cover-uncover test
 Prism cover test
 Maddox rod test
 Measurement of convergence and
accommodation
 Measurement of convergence and
accommodation

37. MANAGEMENT
 Treatment is indicated in decompensated
heterophoria
 Correction of refractive error
 Orthoptic treatment (It is indicated in patients with
heterophoria without refractive error and in
those where heterophoria and/or symptoms are
not corrected by glasses)
 Prescription of prism in glasses (Exercising)
 General Treatment (Avoid prolonged near work,
general fatigue, mental anxiety)
NO
SYMPTOMS
NO
TREATMENT

38. SURGICAL CORRECTION OF
HETEROPHORIA?
DISCUSSION SESSION

39. CONCOMITANT STRABISMUS
 It is a type of manifest squint in which the amount
of deviation in the squinting eye remains constant
(unaltered) in all the directions of gaze; and there
is no associated limitation of ocular movements.

40. Etiology
 It is not clearly defined. The causative factors
differ in individual cases.
 the binocular vision and coordination of ocular
movements are not present at birth but are
acquired in the early childhood. The process
starts by the age of 3-6 months and is completed
up to 5-6 years. Therefore, any obstacle to the
development of these processes may result in
concomitant squint. These obstacles can be
arranged into three groups, namely: sensory,
motor and central

41. Sensory obstacles
 These are the factors which hinder the
formation of a clear image in one eye. These
include:
 Refractive errors,
 Prolonged use of incorrect spectacles,
 Anisometropia,
 Corneal opacities,
 Lenticular opacities,
 Diseases of macula (e.g., central chorioretinitis),
 Optic atrophy, and
 Obstruction in the pupillary area due to
congenital ptosis.

42. Motor obstacles
 These factors hinder the maintenance of the
two eyes in the correct positional relationship. A
few such factors are:
 Congenital abnormalities of the shape and size
of the orbit,
 Abnormalities of extraocular muscles such as
faulty insertion, faulty innervation and
mildparesis,
 Abnormalities of accommodation, convergence
and AC/A ratio.

43. Central obstacles
 These may be in the form of:
 Deficient development of fusion faculty, or
Abnormalities of cortical control of ocular
movements as occurs in mental trauma.

44. Types of concomitant
squint
 Three common types of concomitant squint are :
 1. Convergent squint (esotropia)
 2. Divergent squint (exotropia),
 3. Vertical squint.

45.  Convergent concomitant squint can be further
classified into following types:
 Accommodative esotropia.
 Non-accommodative esotropias.
 Secondary esotropia.

46. Accommodative esotropia.
 It occurs due to overaction of convergence
associated with accommodation reflex. It is of three
types: refractive, non-refractive and mixed.

47. Refractive accommodative esotropia:
 It usually develops at the age of 2 to 3 years and
is associated with high hypermetropia (+4 to +7
D). Mostly it is for near and distance (marginally
more for near) and fully correctable by use of
spectacles.

48. Non-refractive accommodative
esotropia:
 It is caused by abnormally AC/A (accommodative
convergence/accommodation) ratio. This may
occur even in patients with no refractive error.
 Esotropia is greater for near than that for distance
(minimal or no deviation for distance). It is fully
corrected by adding +3 DS for near vision.

49. Mixed accommodative esotropia:
 It is caused by combination of hypermetropia and
high AC/A ratio. Esotropia for distance is
corrected by correction of hypermetropia; and the
residual esotropia for near is corrected by an
addition of +3 DS lens.

50. esotropias.
 This group includes all those primary esodeviations in
which amount of deviation is not affected by the state of
accommodation. It includes:
 i. Essential infantile esotropia. It usually presents at 1-2
months of age.. It is characterised by fairly large angle of
squint (> 30o), alternate fixation in primary gaze and
crossed fixation in lateral gaze.
 ii. Essential acquired or late onset esotropia. It typically
occurs during first few years of life.
Secondary esotropia.
i. Sensory deprivation esotropia. It results from monocular
lesions (in childhood) which either
prevent the development of normal binocular vision or
interfere with its maintenance. Examples
of such lesions are: cataract, severe congenital ptosis, and
so on.

51. DIVERGENT SQUINT
 Concomitant divergent squint (exotropia) is
characterised by outward deviation of one eye while the
other eye fixates.

52. Clinico-etiological types
 1. Congenital exotropia. It is rare and almost always
present at birth.
 2. Primary exotropia. It is a common variety of
exodeviation (unilateral or alternating). It presents with
variable features. It may be of:
 Convergence insufficiency type (exotropia greater or near
than distance),
 Divergence excess (exotropia greater for distance than
near)
 Basic non-specific type (exotropia equal for near and
distance).
 3. Secondary (sensory deprivation) exotropia.
 4. Consecutive exotropia.

53. MANAGEMENT OF CONCOMITANT
STRABISMUS
 Goals of treatment. These are to achieve good
cosmetic correction, to improve visual acuity and
to maintain binocular single vision. However,
many time it is not possible to achieve all the
goals in every case.

54. Treatment modalities.
 These include the following:
 1. Spectacles with full correction of refractive
error should be prescribed in every case. It will
improve the visual acuity and at times may
correct the squint partially or completely (as in
accommodative squint).
 2. Occlusion therapy. It is indicated in the
presence of amblyopia. After correcting the
refractive error, the normal eye is occluded and
the patient is advised to use the squinting eye.
Regular followups are done in squint clinic.
Occlusion helps to improve the vision in children
below the age of 10 years.

55.  3. Squint surgery. It is required in most of the cases to
correct the deviation. However, it should always be
instituted after the correction of refractive error and
treatment of amblyopia.
 Basic principles of squint surgery. These are to
weaken the strong muscle by recession (shifting the
insertion posteriorly) or tonstrengthen the weak muscle
by resection (shortening the muscle).
 Type and amount of muscle surgery. It depends upon
the type and angle of squint, age of patient, duration of
the squint and the visual status. Therefore, degree of
correction versus amount of extraocular muscle
manipulation required cannot be mathematically
determined. However, roughly 1 mm resection of medial
rectus (MR) will correct about 1°-1.5° and 1 mm
recession will correct about 2°-2.5°. While 1 mm
resection and recession of lateral rectus (LR) muscle will

56.  4. Postoperative orthoptic exercises.
These are required to improve fusional
range and maintain binocular single
vision.

57. PARALYTIC STRABISMUS
 It refers to ocular deviation resulting from
complete or incomplete paralysis of one or more
extraocular muscles.
 The lesions may be neurogenic, myogenic or at
the level of neuromuscular junction.

58. RESTRICTIVE SQUINT
 In restrictive squint, the extraocular muscle is not
paralysed but its movement is mechanically
restricted.
 Restrictive squints are characterized by a smaller
ocular deviation in primary position in proportion
to the limitation of movement and a positive
forced duction test

59. SURGERY IN PARALYTIC STRABISMUS
?
DISCUSSION SESSION

60. REFERENCES
 American Academy Of Ophthalmolgy
 Binocular Vision and Ocular Motility Noorden 6th
edition
 Kanski's Clinical Ophthalmology - 8th Edition
 Comperhensive Ophthalmology A K Khurana 4th
Edition

61. THANK YOU
THE END