Ocular motility and strabismus

 Visual axis—passes from the fovea,
through the nodal point of the eye to the
point of fixation (object of regard). The
fovea is usually slightly temporal to the
geometrical centre of the posterior pole
so that visual axis cuts cornea slightly
nasally.
 Anatomical axis—passes from the
posterior pole through the centre of the
cornea.
6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 2

 Angle kappa—between anatomical
and visual axis and it is about 5
degree. It is usually positive when
nasally and negative when
temporally.

 The lateral and medial walls of the orbit
are at an angle of 45 degree to each
other. So the orbital axis forms an angle
of 22.5 degree with both lateral and
medial walls. In primary position of the
gaze the visual axis forms about 23
degree with the orbital axis.

 The eyeball is moved chiefly by six
extrinsic muscles: four recti and two
oblique muscles .
 The four recti arise from a common
tendinous ring that surrounds the optic
canal and a part of the superior orbital
fissure.
 The four muscles are inserted into the
anterior portion of the sclera, 6-8 mm
posterior to the sclerocorneal junction
(limbus).

 The distance from the midpoint of the
rectus muscle tendons to the limbus is
approximately 5.5 mm, 6.5 mm, 7.0
mm, and 7.5 mm for the medial,
inferior, lateral, and superior rectus
muscles, respectively. This
configuration describes the spiral of
Tillaux.

 The superior oblique muscle arises from the
sphenoid bone superomedial to the optic
canal. It passes anteriorward, superior to
the medial rectus, and through a
cartilaginous pulley (the trochlea) attached
to the frontal bone. The tendon is thereby
directed posterolaterally, running inferior to
the tendon of the superior rectus to insert
into the posterior sclera.
 The inferior oblique muscle arises from the
maxilla at the anteromedial floor of the
orbit, passes in a posterolateral direction,
immediately inferior to the inferior rectus to
insert into the posterior lower temporal
quadrant of the globe close to the
macula.

 The superior oblique muscle is supplied
by the trochlear nerve(4th), the lateral
rectus by the abducent nerve(6th), and
the others by the oculomotor(3rd)
nerve.(LR6SO4)

 The horizontal lateral and medial
rectus muscles are purely horizontal
movers on the vertical Z- axis and
have only primary action. The medial
rectus is inserted 5.5 mm behind the
nasal limbus and its sole action is
adduction while the lateral rectus is
inserted 7.0 mm behind the temporal
limbus and its sole action is abduction.

 The vertical superior and inferior rectus
muscles run in line with orbital axis so
forms an angle of 23 degree with
visual axis. The superior rectus is
inserted 7.5 mm behind the superior
limbus and its primary action is
elevation while secondary actions are
adduction and intorsion. The inferior
rectus is inserted 6.5 mm behind the
inferior limbus and its primary action is
depression while secondary actions are
adduction and extorsion.6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 14

 The primary action superior oblique is
intorsion and secondary actions are
depression and abduction.
 The primary action inferior oblique is
extorsion and secondary actions are
elevation and abduction.

 The oculomotor (third cranial) nerve supplies all the
muscles of the eyeball except the superior oblique and
the lateral rectus muscles.
 The oculomotor nerve supplies the levator palpebrae
superioris and superior rectus (by its superior division) and
the medial rectus, inferior rectus, and inferior oblique
muscle (by its inferior division).
 A parasympathetic communication arises from the nerve
branch to the inferior oblique muscle.
 This nerve enters the ciliary ganglion and synapses there.
 Postganglionic parasympathetic nerve fibers pass from the
ganglion to the eyeball through the short cilliary nerves,
innervating the sphincter pupillae and ciliary muscle.
 In the act of focusing the eyes on a near object the
oculomotor nerves are involved in adduction (medial
recti), accommodation (ciliary muscle), and miosis
(sphincter pupillae).
 Paralysis of the oculomotor nerve results in ptosis (paralysis
of the levator), abduction (unopposed lateral rectus), and
other signs. 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 17

 The trochlear (fourth cranial) nerve
supplies only the superior oblique muscle
of the eyeball.
 It emerges from the dorsum of the brain
stem.
 The trochlear nerve is tested by asking
the subject to look downward when the
eye is in adduction.

 The abducent (sixth cranial) nerve
supplies only the lateral rectus muscle of
the eyeball.
 It is bending sharply anteriorward across
the superior border of the apical portion
of the petrous part of the temporal
bone.
 This perhaps accounts for abducent
involvement in almost any cerebral
lesion that is accompanied by increased
intracranial pressure.

 The ciliary ganglion is the peripheral ganglion of
the parasympathetic system of the eye. It is
situated between the optic nerve and the
lateral rectus .
 The postganglionic parasympathetic fibers pass
to the short ciliary nerves (which are branches of
the ganglion) and supply the ciliary muscle and
sphincter pupillae.
 Postganglionic sympathetic fibers from the
internal carotid plexus reach and pass through
the ciliary ganglion. By way of the short ciliary
nerves, the sympathetic fibers supply the dilator
pupillae and blood vessels, as well as smooth
muscle in the eyelid (superior tarsal muscle) and
in the inferior orbital fissure (orbitalis). A
sympathetic lesion (Horner syndrome) results in a
small pupil (miosis) and mild ptosis .

a)ductions—movement of one eye only
 Adduction(medial movement)
 Abduction(lateral movement)
 Supraduction(elevation)
 Infraduction(depression)
 Incycloduction(intortion)
 Excycloduction(extortion)
Agonist—it is the primary muscle moving the eye in
any one direction
Synergist—a muscle which act together with the
agonist
Antagonist—a muscle which acts in the opposite
direction to the agonist
Sherringtons law of reciprocal innervations—when
the agonist contracts then the antagonist relaxes

b)versions—binocular movements in the same
direction
 Dextroversion(right gaze)
 Levoversion(left gaze)
 Supraversion(up gaze)
 Infraversion(down gaze)
Above 4 are the secondary positions of gaze
 Dextro elevation
 Dextro depression
 Laevo elevation
 Laevo depression
Above 4 are tertiary position of gaze

Six cardinal position of the gaze-
 Dextroversion
 Laevoversion
 Dextro elevation
 Laevo elevation
 Dextro depression
 Laevo depression
Yoke muscle—a muscle of one eye is paired with
a muscle of the other eye while moving the
eye into each of the six cardinal position of
gaze
 Dextroversion(LR of right eye & MR of left eye)
 Dextroelevation(SR of right eye & IO of left eye)

Herings law of equal innervations—it says
that during any conjugate eye
movement equal and simultaneous
innervations follows to the yoke muscle.
So a paresis of one muscle is associated
with over action of its yoke muscle or
contra lateral synergist and it results in
more secondary angle deviation in
paralytic squint.

c)vergences—binocular movements but in
the opposite directions(convergence &
divergence). Divergence is the turning
outward while convergence is the turning
inward of the both eyes. The convergence
may be voluntary or reflux. The reflux
convergences are of four types—
 Tonic-due to inherent tone of medial recti
 Proximal-due to psychological awareness
of a near object

 Fusional-which is maintained by
binocular single vision, so that similar
images are projected onto the
corresponding retina.
 Accommodative-each dioptre of
accommodation is accompanied by a
constant increment in accomodative
convergence, giving the AC/A ratio. This
is the amount of convergence in prism
dioptre (∆) per dioptre (D). The normal
value is 3-5 ∆. This means that 1 D of
accommodation is associated with 3-5 ∆
of accommodative convergence.

d)supra nuclear eye movements—
 Saccades--rapid, voluntary, refixating
eye movements
 Pursuits—smooth following movements to
maintain vision on a slow moving object
 Vestibulo-ocular movements—vestibular
nystagmus in caloric test

 it is the co-ordinated use of the two eyes to produce a single
unified image. It is not present at birth but develops later with
Clear vision in both eyes
Co-ordination between both eyes in all directions of gaze
Ability of brain to fuse
a)simultaneous macular perception—ability to see two
dissimilar images simultaneously and to super impose them
b)fusion—ability to see the slightly dissimilar images formed in
each eye and blended them into one. The fusional vergence
may be decreased by fatigue or illness, converting a phoria to a
tropia. It can be increased by orthoptic exercises. The normal
values are
 Convergence (adduction)—15 ∆ for distance and 25 ∆ for near. It
controls exophoria
 Divergence (abduction)-- 6 ∆ for distance and 12 ∆ for near. It
controls esophoria
 Vertical—2-3 ∆
 Cyclovergence—about 2-3 degree
c)stereopsis—depth perception by two eyes

 Confusion—the simultaneous
appreciation of two superimposed but
dissimilar images caused by stimulation
of corresponding points usually fovea by
images of different objects.

 a)physiological diplopia—it is normal phenomenon due to
looking at a near object with attention directed to a distant
object.
 b)uniocular diplopia—when only one eye is open
 Immature cortical cataract
 Subluxated lens
 Large iridectomy, iridodialysis(polycorea)
 Retinal detachment
 c)binocular diplopia—when both eyes are open
 Paralysis of extra ocular muscle
 Displacement of eye ball due to tumour/fracture
 Mechanical restriction of eye movements(pterygium,
symblepharon, thyroid ophthalmopathy
 Decentred spectacles
 Anisoconia (due to aphakic correction of one eye)
 Congenital high anisometrpia
 In case covergent squint uncrossed(homonymous) diplopia
while in divergent squint crossed(heteronymous) diplopia

 a unilateral or bilateral reduction of vision
without any organic ocular lesion. The most
sensitive period of amblyopia to develop is
first 6 months of life and after 6 years
amblyopia usually does not occur. The types
are
Stimulus deprivation amblyopia(amblyopia
exanopia)—caused by congenital cataract,
leucoma, ptosis, occlusion
Strabismic amblyopia
Anisometropic amblyopia
Isoametropic amblyopia(bilateral
amblyopia)
Meridional amblyopia—due to uncorrected
astigmatism and it can be unilateral or
bilateral.

Diagnosis—
 Visual acuity—a difference in BCVA of two or
more lines between two eyes and visual acuity is
good for a single letter than a row of letters.
 Neutral density filters which decrease the visual
acuity in normal/organic lesion of the eye but no
decrease in case of amblyopia.
 Grating (grid pattern) acuity often exceeds
spatial (Snellen) acuity in amblyopia.
 The visual fields and colour vision are normal in
amblyopia.

Treatment—can be treated up to 7-8 years of age
in strabismic amblyopia and up to 11-12 years in
anisometropic amblyopia.
 Removal of opacity in the media
 Full correction of refractive errors
 Sound eye occlusion therapy—it may be total
occlusion(both light and form sense occluded) or
partial occlusion(only form sense occluded)
 Number of days of occlusion equal to the
number of years up to 6 years
 Penalisation by atropine
 Pleoptics and CAM stimulator to increase foveal
fixation

 Suppression— it is the active inhibition by the visual
cortex, of an image from one eye when both eyes are
open. The stimulus for suppression includes diplopia,
confusion and a blurred image resulting from
astigmatism/anisometropia. The central foveal
suppression of the deviated eye occurs in case of
confusion while peripheral retinal suppression occurs in
diplopia. Monocular suppression can leads to
amblyopia while alternating suppression does not
cause amblyopia.
 Abnormal retinal correspondence (ARC)—in this
the non corresponding retinal elements acquire a
common subjective visual direction. The fovea of the
fixating eye is paired with non foveal element of the
deviated eye. It allows some binocular vision with
limited fusion and frequently in small angle esotropia.6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 41

Motor adaptation to strabismus—this involves
the adoption of the abnormal head posture and
occurs in adults who cannot suppress or in
children with binocular vision potential. The
abnormal head posture is to maintain BSV and
to eliminate diplopia. The head is turned in the
direction of the action of weak muscle.
 Horizontally face is turned to right or left
 Vertically chin is elevated or depressed
 Torsionally head is tilted to right or left shoulder

History—
 Early age of onset requires surgery while
later onset likely to be accommodative
type.
 Old photographs are important.
 Intermittent squint suggests some degree
of binocularity while in alternating squint
both eyes have good vision.
 Children with cerebral palsy have
increased incidence of strabismus
 Less gestational period, low birth weight
 Family history

Visual acuity in preverbal child—
 Occlusion of good eye is objected by child
 Fixation test by 16 ∆ base-down prism over one
eye and other eye is occluded.
 Hundreds and thousands sweet test—if child is
able to pick up small sweets at 33 cm then visual
acuity is at least 6/24.
 Brisk rotation test—in case of impaired vision the
nystagmus does not stop after stopping the
rotation.
 Preferential looking test—Teller acuity cards
(black strips of varying thickness) and Cardiff
acuity cards (shapes of variable outlines)
 Pattern visually evoked potential
 Optokinetic nystagmus 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 44

Visual acuity in verbal child—
 At 2 years pictures test (Kay pictures)
 At 3 years single letter optotypes
(Sheridan-Gardiner test)
 At 4 years linear Snellen acuity test
Tests for steriopsis—
 Titmus fly and circles test
 TNO test with red and green spectacles
 Lang test
 Frisby test 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 45

Base out prism test— it is to detect BSV in
children who cannot perform the above
mentioned stereo tests. A 20 ∆ base-out prism
is placed in front of right eye so retinal image
is moved temporally to cause diplopia.
 Right eye will shift to left (right adduction) and
left eye will shift to left (left abduction) in
accordance with Hering law.
 Left eye then will go to corrective right (left re
adduction)
 On prism removal both eyes will go to right
 Left eye will make then left fusional movement

a) Worth four dots test—the patient wears red
lens in right eye (only red colour visible) and
green lens in left eye (only green colour visible).
The patient is shown one red, two green and one
white dot.
 If all four lights are seen—normal/ARC (with
deviated eye)
 Two red lights—left eye suppression
 Three green lights—right eye suppression
 Two red and three green lights—diplopia

Tests for sensory anomalies
Worth four-dot test
a - Prior to use of glasses
b - Normal or ARC
c - Left suppression
Bagolini striated glasses
a - Normal or ARC
b- Diplopia
c - Suppression
d - Right suppression
e - Diplopia
d - Small suppression scotoma

b) Bagolini striated glasses—to convert
a point light source into a line. Two lenses
are placed at 45 and 135 degree in front
of each eye and the patient fixates a
point light source.
 If an X- is visible then the patient is
either orthophoric or ARC (if strabismic)
 It two line do not cross then diplopia
 If one line only then other eye is
suppressed
 If a small central gap in one line then
central macular suppression

c) After image test—this test
demonstrates the visual direction of the
foveae. The one fovea is stimulated by
vertical bright flash light and other fovea
is stimulated by horizontal flash light. The
patient is asked to draw the relative
positions of the after image. Results are
 If two images cross each other then
normal retinal correspondence
 If two images do not cross each other
then ARC
 If esotropia with ARC the horizontal
image (if presented to right eye) is seen
to the left and reversed in exotro6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 53

Synaptophore—it is an instrument for assessing
strabismus and quantifying binocular vision. It has two
cylindrical tubes and a +6.5 D lens in each eyepiece.
This optically sets the testing distance at about 6
meters. The different pictures are inserted into the
slide carriers. It gives the grades of binocular vision
 Simultaneous perception (first grade)—two
dissimilar images are shown like a bird and a cage,
then the patient is asked what he sees. If two pictures
are not seen simultaneously then either suppression or
significant amblyopia.
 Fusion (second grade)—the ability of two eyes to
produce a composite picture from two similar pictures
each of which is incomplete in one small different
detail.
 Steriopsis (third grade)—depth perception by the
superimposition of two pictures of the same object
which have been taken from slightly different angles.6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 54

 Hirschberg corneal reflection test (1mm
=70 deviation)—a rough objective estimation
of the angle of squint. A torch light is shone
into the patients eyes at a arms distance. Each
1 mm difference is equal to 7 degree/15 ∆. If
reflex is at pupillary border then angle is about
15 degree and if at the limbus then angle is
about 45 degree.

Hirschberg test
• Rough measure of deviation
• Note location of corneal light reflex
Reflex at border of pupil = 15 Reflex at limbus = 45
• 1 mm = 7 or 15

 Krimsky prism reflex test—the prisms
are placed in front of the fixating eye until
the corneal light reflexes are symmetrical.
It measures only manifest deviation but
not latent deviaton.

 Prism bar cover test(PBCT)—10
deviation=2 prism dioptres
 Perimeter/tangent screen
 Synaptophore

1. Cover tests--
 Cover-uncover test—by far the most accurate
assessment of a deviation is with cover tests. The
tropias can be differentiated from phorias. The cover
and uncover test has two parts
 Cover test to detect a hetrotropia. It should be done
both for near and distance. If right deviation is
suspected then left eye is covered and movement in
right eye is noticed. No movement means
orthophoria/lefty heterotropia. Adduction of right eye
means exotropia while abduction of right eye means
esotropia. Down movement means hypertropia and
up movement means hypotropia.

 Uncover test to detect a hetrophoria. It
should be done both for near and
distance. The examiner covers the right
eye uncovers it after a few seconds. No
movement means orthophoria. Adduction
of right eye indicates exophoria while
abduction indicates esophoria. Up/down
movements indicate vertical phorias.

Cover tests
Cover test detects heterotropia • Prism cover test measures total deviatio
Alternate cover test detects total deviation
Uncover test detects heterophoria

2. Alternate cover test—it interrupts binocular fusion
and reveals total deviation (phoria + tropia). The eye
is occluded for 2 sec then other eye is occluded for 2
sec and then repeated several times. After the cover
is removed, then smoothness and speed of recovery is
noted as the eyes return to their pre dissociated state.
 Patient with heterophoria will have straight eyes before
and after the test
 Patient with heterotropia will have a manifest deviation
3. Prism cover test—it precisely measures the angle of
deviation. The prisms of increasing strength are placed
in front of one eye with apex in the direction of the
deviation. The alternate cover test is continuously
performed and stronger prisms are brought in till the
end point is reached with no further eye movement. At
this point the angle of deviation is equal to the
strength of prism.

a) Maddox wing— it dissociates the eyes for
near fixation (1/3 m) and measures
heterophoria. The right eye sees only a white
vertical arrow and a red horizontal arrow
whereas left eye sees horizontal and vertical
rows of numbers.
 The horizontal deviation is measured by asking
the patient at which number white arrow
points
 Vertical deviation is measured by red arrow
 Cyclophoria is determined by asking the
patient to rotate the red arrow until it is
parallel with the horizontal row of numbers

b) Maddox rod—consists of fused cylindrical
red/white glass rors which converts a point
light source into a line 90 degree to the axis of
the rods.
 Rod is placed in the right eye, this dissociates
the two eyes so that line is seen by right eye
and point source by left eye and in case of
squint they are not superimposed
 Amount of deviation is measured by
superimposing two images with the help of
prism (apex towards the deviation)
 This test cannot differentiate phoria from
tropia
 Ocular movements (versions and ductions) are
checked 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 67

 Near point of convergence (NPC)—the
nearest point on which the eyes can maintain
fixation and it is measured with the RAF rule
which rests on patient`s cheeks. The target is
slowly moved along the rule towards the
patient until one eye loses fixation and drifts
laterally (objective NPC). The subjective NPC is
the point at which patient reports diplopia. The
normal NPC should be nearer than 10 cm.
 Near point of accomodation (NPA)—the
nearest point on which the eyes can maintain
clear focus and also measured by RAF rule. At
the age of 20 years it is 8 cm and at 50 years
it is 46 cm. 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 71

 Refraction under cyclopegia—to
check hypermetropia, astigmatism,
anisometropia, myopia
 Fundoscopy—to rule out macular
scarring, optic disc hypoplasia,
retinoblastoma

It is the misalignment of the two eyes while
orthophoria is the perfect ocular alignment
without any effort. When a child develops squint,
the following changes occurs
 The fovea of the squinting eye is suppressed to
avoid confusion
 Diplopia occurs because non corresponding
retinal elements receive same image
 To avoid diplopia the patient will develop either
peripheral suppression of the squinting eye or
ARC
 If suppression occurs this will lead to strabismic
amblyopia

A)apparent squint(pseudo strabismus)
B)latent squint(heterophoria)
C)manifest squint(hetrotropia)
 Concomitant (non paralytic) squint
 Non concomitant (paralytic) squint

Apparent squint (pseudo strabismus)-- it
can be pseudo-esotropia or exotropia.
a) Pseudo-esotropia—
 Epicanthic folds
 Short inter pupillary distance
 Negative angle kappa—it is the angle between visual
and anatomical axes. Normally fovea is slightly
temporal so when a light is shone onto the cornea,
then reflex will be just nasal to the centre of the both
eyes. It is termed as positive angle of kappa but when
fovea is nasal (high myopia, ectopic fovea) then angle
kappa will be negative.
b) Pseudo-exotropia—
 Wide interpupillary distance
 Positive angle kappa

Pseudo-deviations
Pseudo-esotropia
Epicanthic folds
Short interpupillary distance
Negative angle kappa
Pseudo-exotropia
• Wide interpupillary distance
• Positive angle kappa

 the eye has a tendency to deviate but
prevented by the fusion mechanism to
have binocular single vision.Under stress
or when fusion is interrupted, the
deviation becomes manifest.
 Exophoria—eye tends to deviate
outwards
 Esophoria—eye tends to deviate inwards
 Hyperphoria—eye tends to deviate
upwards
 Cyclophoria—tortional deviation
 In general esophoria more in
hypermetropes and exophoria more in
myopes & presbyopes

Symptoms—
 Blurred vision
 Headache and eye ache
 Intermittent diplopia
Diagnosis—
 Cover test
 Maddox rod test
 Prism vergence test
 Synaptophore

 Smaller degree –not treated
 Errors of refraction corrected
 Orthoptic exercise to increase fusion
 Exercises with adverse prism(base of the
prism towards the direction of deviation)
 Relief of symptoms with prism(apex of
the prism towards the direction of
deviation)
 Operation is rarely indicated

 it is the dissociation of the eyes where the angle of
deviation remains the same in all directions of gaze.
The causes are
 Poor vision in one eye due to refractive errors, media
opacity, retinal & optic nerve diseases
 Disturbances of ocular muscle insertion/mal
development
 Dissociation between accommodation and
convergence relationship(in hypermetropes more
accommodation causing convergent squint and in
myopes less accommodation causing divergent squint
 Decomensated heterophoria leading to heterotropia
 Central causes are cerebral palsy, mental retardation,
deficient fusion

 in about 85% cases one eye takes up
fixation and other eye becomes squinting. It
may be
 Convergent—one eye deviates inwards
and caused by amblyopia(more),
hypermetropia, esophoria, orbital
asymmetry
 Divergent—one eye deviates outwards and
caused by amblyopia(less), myopia,
secondary divergent squint(blind eye at
rest), over correction of convergent squint
 Vertical—rare

 when one eye fixes the other eye
deviates and either of the eyes can
adopt fixation alternately.
 In this the visual acuity remains
normal/near normal in both eyes.
 There is no diplopia as the image formed
by the deviating eye is suppressed by
the brain.

 No symptoms/no diplopia
 In case of monocular squint the visual
acuity is poor(strabismic amblyopia)
 No limitation of ocular movements
 Primary angle of deviation is equal to
secondary angle of deviation
Primary angle—the deviation of the
squinting eye when other eye is fixed
Secondary angle—the deviation of the
normal eye under cover when squinting
eye is fixed

Accomodative type
 Refractive (fully accommodative/partially
accommodative)
 Non-refractive (with convergence
excess/accommodation weakness)
 Mixed accomodative

Non-accomodative
 Essential infantile
 Microtropia
 Basic—no significant refractive error with equal
deviation for near and distance. It is treated
surgically.
 Convergence excess-- no significant refractive
error with orthophoria/small esophoria for distance
and esotropia for near. Normal or low AC/A ratio with
normal near point of accommodation. Treated with
bilateral medial rectus recession.
 Divergence insufficiency—occurs in young healthy
adults with intermittent or constant esotropia for
distance. Full abduction bilaterally and treated
prisms/bilateral lateral rectus resections.

 Divergence paralysis—at any age and difficult to
differentiate with uni/bilateral lateral rectus palsy but
comitant. The esotropia is unchanged or decrease on
lateroversion (unlike a 6th nerve palsy). Neurological
causes such as head trauma, ICSOL and
cerebrovascular accidents may be present.
 Sensory esotropia—caused by unilateral cataract,
optic nerve atrophy/hypoplasia, toxoplasma
retinochroiditis and retinoblastoma.
 Consecutive esotropia—following surgical
overcorrection of an exodeviation.
 Acute onset
 Cyclic oculomotor spasm—usually hysterical an
intermittent phenomenon or occasionally with
trauma/posterior fossa tumour. During attack
esotropia with pseudo-myopia due to accommodative
spasm and bilateral miosis. Treated with cycloplegics

 Refractive accommodative esotropia—it
is due to high hypermetropia (between
+4 and +7 D) and AC/A ratio is normal.
The magnitude of deviation is usually <10
∆ and varies little between distance and
near. The fully accommodative type is
completely eliminated by optical
correction of hypermetropia while partial
type is reduced but not eliminated by
the correction of hypermetropia.

 Non-refractive accommodative esotropia—it is
associated by high AC/A ratio. In this one unit
increase of accommodation is accompanied by
a disproportionately large increase of
convergence in the absence of significant
hypermetropia.
a) Convergence excess type—characterised by
high AC/A ratio due to increased convergence
while accommodation is normal. Normal near
point of accommodation. The eyes are straight
for distance but esotropia for near.
b) Hypoaccomodative type—high AC/A ratio due
to decreased accommodation so extra effort of
accommodation is used for near with more
convergence. The near point of
accommodation is increased.6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 99

 Mixed accommodative esotropia—
hypermetropia and high AC/A ratio may
coexist, so esotropia for distance which
increases >10 ∆ on near fixation. The
distant deviation is usually corrected by
spectacles but for near esotropia patient
should wear bifocals.

H/O
 age of onset, acute illness,
 family history,
 intermittent or constant,
 unilateral/alternating, diplopia
 head posture to differentiate from paralytic squint
examination—
 visual acuity
 refraction under atropine(to find out refractive errors)
 ocular motility limitation
 foveal or extra foveal fixation
 anterior segment & fundus
 cover test to find out uniocular/alternating type6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 101

 Hirschberg corneal reflection test(1mm=70
deviation)—at papillary margin=150 and at
limbus=450
 Krimsky prism reflex test
 Prism bar cover test(PBCT)—10 deviation=2
prism dioptres
 Perimeter/tangent screen
 Synaptophore
 worth 4 dot test

 The aim is to make eye straight and to
ensure binocular single vision. The
prognosis decrease after 6 years and in
adults the surgical correction is purely for
cosmetic reason(4 Os)---

 Optical correction of refractive error--in children
less than 6 years a full cycloplegic refraction
revealed on retinoscopy should be prescribed. In
fully accommodative type esotropia this will
control the deviation both for near and distance.
After the age of 8 years the retinoscopy should
be done without cycloplegia and maximum plus
glasses that can be tolerated are prescribed. The
executive type bifocals are prescribed in case of
mixed accommodative type.

 Miotic therapy—used for short term in children
with accomodative esotropia due to high AC/A
ratio, who will not wear spectacles. 0.125%
ecothiopate iodide e. d. once/ day or 4%
pilocarpine qid for 6 weeks. This will cause more
peripheral accommodation directly by ciliary
muscle so less accommodative effort will be
used by patient for near vision and thereby less
accommodative convergence. 2.5%
phenylepherine b d can be used with
ecothiopate to decrease iris cyst formation.
 Occlusion therapy to treat amblyopia
 Orthoptic exercises
 Operative procedures-- when deviation is not
fully corrected by spectacles.6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 105

a)weakening procedures
 Recession--it slackens a muscle by
moving its insertion towards its origin. It
can be done for any extraocular muscle
except the superior oblique.

 Marginal myotomy
 Myectomy--severing the muscle from its
insertion without reattachment.
Commonly used for overacting inferior
oblique and sometimes for contracted
rectus.
 Tenotomy

 Fadens procedure(posterior fixation
suture)--to decrease the pull of the
muscle in its field of action without
affecting its primary position. The belly of
the muscle is sutured with a non
absorbable suture a few mm behind to
its insertion.

b)strengthening procedures
 Resection—to shorten a muscle to
enhance its effective pull.
 Advancement—to bring muscle nearer
to the limbus.
 Tucking (plication)—the muscle or its
tendon is reserved to enhance the
action of SO muscle in congenital 4th
nerve palsy.

 1 mm resection/recession of MR corrects 30 of
deviation
 1 mm resection/recession of LR corrects 20 of
deviation
 Medial rectus should not be recessed more
than 5.5 mm as this will cause convergence
deficiency and should not be resected more
than 5.5 mm as this will cause retraction of
the globe and narrow palpebral fissure
 The resection and recession limits for lateral
rectus are 7 mm.
 It is preferred to operate on elevators rather
than depressors

Convergent squint—
 MR recession & LR resection(in
squinting eye)
 Bimedial recession(in both eyes)
Divergent squint—
 LR recession & MR resection(in
squinting eye)
 Bilateral recession(in both eyes)

Essential infantile esotropia— An idiopathic within
first 6 month of life with no significant refractive
error and no ocular movement limitation.
 The angle is usually large >30 ∆
 Alternating fixation in primary gaze and cross
fixation in side gaze so right eye is used in left
gaze and left eye is used in right gaze.
 Nystagmus latent or manifest type and usually
horizontal
 Inferior oblique over action may present
 Dissociated vertical deviation in 80% cases by
the age of 3 years.

Differential diagnosis—
 Congenital bilateral sixth nerve palsy
 Sensory esotropia due to organic eye disease
 Nystagmus blockade syndrome in which convergence
dampens a horizontal nystagmus
 Duanes syndromes type I & III
 Mobius syndrome
 Strabismus fixus (due to fibrosis)
Management of essential infantile esotropia—the eyes
should be surgically aligned by the age of 12 months but
only after amblyopia or significant refractive error have
been corrected. Any associated over action of the
inferior oblique should be corrected. Treatment for
amblyopia (develops in 50% cases) and DVD should be
done.

 Dissociated vertical deviation (DVD)—
under cover up-drift with
excyclodeviation of the eye but when
cover is removed the affected eye
moves down without corresponding
down movement in the other eye. So
DVD does not obey Hering law. It is
treated by superior rectus recession with
or without a Faden procedure and/or
inferior oblique anterior transposition.

Microtropia (monofixation syndrome)—it
may be primary or after surgery for a large
deviation.
 Anisometropia in nearly all cases,
commonly with hypermetropia or
hypermetropic astigmatism
 Very small angle less than 8 ∆ which may or
may not be detected with cover test
 Central suppression scotoma of the
deviating eye prevents confusion
 Bagolini striated glasses show a cross with a
gap in the oblique line

 4 ∆ base-out prism is placed in front of
the normal eye, the image is moved
from the fovea to the parafoveal
temporal point resulting in a re-fixation
movement. No movement will occur
in the microtropic eye since the
image is moved within the central
suppression scotoma.
 Treated with spectacle correction of
anisometropia and occlusion for
amblyopia but bifoveal fixation never
occurs. 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 117

I. Constant types
 Congenital exotropia—present at birth with large and
constant angle with normal refraction. DVD and
neurological anomalies may be present. Treated with
bilateral rectus recessions combined with one or both
medial recti resection.
 Sensory—due to monocular/binocular impairment of
vision in children more than 5 years or in adults.
 Consecutive—following over correction of an
esodeviation
II. intermittent types—present around 2 years
 Basic—deviation same for distance and near
 Convergence weakness—in older children and adults.
The angle of deviation is greater for near.
 Divergence excess-- The angle of deviation is greater for
distance. 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 118

 It is the misalignment of the visual axis as
a result of paresis/paralysis of one or
more extra ocular muscles.
 The angle of deviation varies in different
directions of the gaze.

a) Lesions affecting cranial nerves
(neurogenic)—
 Supranuclear or internuclear
 Nuclear lesions—cerebrovascular diseases,
infections(encephalitis, meningitis,
peripheral neuritis, neurosyphilis), neoplasms
 Lesions of nerves—congenital hypoplasia,
head injury, meningitis, cavernous sinus
thrombosis
 Vascular lesions—hypertension, diabeties,
haemorrhage, thrombosis, atherosclerosis
 Direct or indirect trauma to nerves
 Carbon monoxide poisoning ,diphtheria
toxin, alcoholic and lead neuropathy
 Demyelinatig lesions like multiple sclerosis

b)Lesions of extra ocular muscles
(myogenic)—
 Congenital absence or hypoplasia of
muscles
 Injury of muscles
 Inflammatory lesions like myositis after
influenza, measles etc
 Myopathies, myasthenia gravis, thyroid
diseases

 Crossed (divergent squint)/uncrossed
diplopia (convergent squint)
 False orientation of the objects
 Vertigo and nausea
 Visual acuity is normal in both eyes
 Secondary angle of deviation is more
than the primary angle of deviation
 Restricted ocular movement in the
direction of action of paralysed muscle
 Compensatory head posture(head
turned in the direction of action of
paralysed muscle)

a) Total ophthalmoplegia—both intrinsic and
extrinsic muscles are paralysed. The clinical
features are
 Slight proptosis and divergent
position(anatomical rest position)
 Ptosis
 No movement
 Fixed dilated pupil
 No reaction to light and accommodation
b) External ophthalmoplegia—
 Paralysis of only extrinsic muscles
 Papillary reaction and accommodation
normal

c) Oculomotor nerve (3rd) palsy—
 Ptosis due to weak LPS function
 Divergent and slightly down eye ball due to
unopposed action of LR(6th) and SO(4th)
 Intorsion of eye ball on attempted downgaze
due to SO action
 Ocular movements restricted in all directions
except outward(LR action)
 Pupil dilated and not constricts to light or
convergence

d) Trochlear nerve(4th) palsy—
 Trauma is the most common cause
 Abnormal head posture(chin depressed,
head tilt & face turned to the normal
side)
 Diplopia more in the down gaze
 Eye ball deviates upward and
inward(ipsilateral hypertropia)
 Extortion of the globe
 Restricted downward and inward
movement
 Bielschwsky three steps test for diagnosis
of 4th nerve palsy

 The most common type of palsy and
commonly caused by raised ICT
 Eye ball convergent
 Defective abduction
 Face turned in the field of action of the
paralysed muscle

Sequelae of extra ocular muscle palsy
 Over action of contralateral synergist (yoke
muscle)
 Contracture of ipsilateral antagonist
 Inhibitionalpalsy of the contralateral
antagonist
a) Example of right lateral rectus palsy
 Over action of left medial rectus
 Contracture of right medial rectus
 Inhibitional (secondary) palsy of left lateral
rectus
b) Example of superior oblique palsy
 Over action of left inferior rectus
 Contracture of right inferior oblique
 Inhibitional palsy of left superior rectus

 Diplopia charting
 Hess screen chart
 Worth 4 dots test
 Forced duction test(FDT)
 X-ray skull
 CT scan(orbit & brain)
 MRI scan
 Blood sugar level
 Thyroid function tests
 Tensilon test for myasthenia

 Occlusion therapy
 Relieving prism
 Observation for 6 months
 Recession of contra lateral synergist
 Muscle transposition surgery
 Botulinum toxin injection to treat the
antagonist muscle

 Hummelsheim procedure—the medial rectus
is recessed and lateral halves of superior and
inferior recti are disinserted and reattached to
superior and inferior margins of paretic LR
muscle. To avoid postoperative anterior
segment ischaemia the MR recession may be
replaced by botulinum toxin injection.
 Jensen procedure—the splited lateral halves
of superior and inferior recti are sutured with a
non absorbable material superior and inferior
margins of paretic LR muscle with
recession/botulinum toxin injection of MR.

Surgery for superior oblique palsy—the surgery is
done in cases with abnormal head posture and diplopia
unresponsive to prisms.
 Congenital cases with large hypertropia in primary
position are treated with SO tucking.
 Acquired small hypertropias are treated by ipsilateral
IO weakening.
 Acquired moderate to large hypertropias are treated
by ipsilateral IO weakening combined with ipsilateral
SR weakening and/or contralateral IR weakening.
 Acquired pure excyclotropias without hypertropias are
treated by Harada-Ito procedure which involves
splitting and anterolateral transposition of the lateral
half of the superior oblique tendon.

 Adjustable sutures—indicated when a
precise outcome is essential and
conventional procedures are
unpredictable; for example acquired
vertical deviations with thyroid
myopathy, after blowout fracture, 6th
nerve palsy, adult exotropia etc.

Botulinum toxin chemodenervation—it
causes temporary paralysis of an extra
ocular muscle and can be used in
 To determine LR function in 6th nerve
palsy where MR contracture prevents
abduction. So botulinum toxin is injected
into the belly of overacting MR under
electromyographic guidance
 To determine the risk of postoperative
diplopia and to assess the potential of
BSV 6/17/2015Dr. Mohd Najmussadiq Khan, M. S. (Ophth) 143

Ocular motility and strabismus

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