Dr.Puskar Ghosh

PGT

Burdwan Medical College

• It is a condition in which the visual axis of the two eyes does

not meet at the point of regard.

• Greek word-”strabos”:crooked

• PHORIA:latent visual axis deviation,held in check by fusion.

• TROPIA:a manifest visual axis deviation.

• Intermittent Tropia:deviation may exist in only certain gaze

positions or target distance.

• Visual axis (line of vision) : extending from the point of

fixation to the fovea.

• Anatomical (Pupillary) axis:is a line passing from the posterior pole through the centre of the cornea .

• Angle kappa : is the angle subtended by the visual and anatomical axes .

+5˚ exotropic.

5.5

6.6

7.0

7.7

• Uniocularly-Duction

• Binocularly-Version.-Same direction

• Opposite direction-Vergence

• Adduction-nasally horizontal

• Abduction-temporally horizontal

• Sursumduction or elevation-upward

• Deorsumduction or depression-downward

• Incycloduction

• Excycloduction

Yoke musclesFor co ordinated eye

movements one muscle of the

each eye act togather.These

are called yoke muscle.

• Hering’s law,for a

binocular movement the

corresponding muscle

(yoked) receive equal and

simultaneous innervation.

• Sherington’s law of

reciprocal innervation,for

any binocular movement the

direct antagonist receives

an equal and simultaneous

inhibition of its innervation.

• Definition:

It is the state of simultaneous vision with two seeing eyes that

occurs when a person fixes his visual attention on an object of

regard.

• Simultaneous perception

• Fusion

• Stereopsis

Ability to fuse points

outside corresponding

retinal area

Ability to fuse

image projected in

corresponding

retinal pints

Ability of

perception of depth

• Confusion-

due to different image viewed by two fovea

Immediately checked by cortical or retinal rivalry mechanism.

• Diplopia-

one object is perceived by one of the fovea of one eye and other object is perceived by extrafoveal point of the other eye which has a different localization value in space.

Binocular diplopia-single image on closing one eye

Monocular diplopia-in astigmatism,neurological conditions

Uncrossed diplopia-esodeviation

Crossed diplopia-exodeviation

• Motor Adaptation:

1. Fusion

• Beyond fusional reserve-asthenopia

1. Head postures

• Chin elevation or depression

• Face turn

• Head tilt

3. Blind spot mechanism:

esotropia of 15˚,other image falls

On blind spot-no diplopia.

• Sensory Adaptation:

• Supression:

Confusion is takled by foveal rivalry which is actually a

suppression.

extrafoveal image suppression is readily occurs if the

visual potential of the extrafoveal point is poor.

Facultative

Obligatory

• Anomalous Retinal Correspondence:

It is the binocular functional adaptation to strabismus at

the cortical level.The fovea of the fixing eye develops a

correspondence (binocular relationship) with an

extrafoveal point of the other eye.

• orthophoria ; perfect alignment of the visual

axes. Most individuals have heterophoria.

• Hypophoria/hypertropia; latent/manifest

squint downwards turning of eyes

• Hyperphoria/hypertropia; latent/manifest

squint upwards turning of eyes

• Exophoria; latent squint outwards turning of the eyes

• Exotropia; manifest squint outwards turning of the eyes

• Esophoria; latent squint inwards turning of the eyes

• Esotropia; manifest squint inwards turning of the eyes

Strabismus

Concomitant:deviation same in all gaze Incomitant:inequal deviation

Horizontal

1. Esotropia

2. Exotropia

Vertical

1. Hypertropia

2. Hypotropia

Torsional

1. Incyclotropia

2. Excyclotropia

Underaction Overaction

Restrictive Paralytic

Neurogenic

1. Supraneuclear

2. Infraneuclear

3. Neuclear

Myogenic

INCOMITANT CONCOMITANT

Age Late early

Magnitude of squint Varies with eye position Same in all gazes

Diplopia Present Usually absent

Onset Sudden Gradual

Precipitating event Head injury Rare

Head posture Present Absent

Secondary deviation >primary =primary

Ocular movement Restricted Full

False projection Present Absent

Mechanism Defect in efferent

pathway

Defect in afferent path

Or central mechanism

Sensory adaptation Rare frequent

Cyclotropia Usually present Absent (expt A,V

patterns)

• History:

H/O present illness-

• Age of onset

• Duration of the squint

• Chief Complaints:

• Symptoms-

• Asthenopia:

• Uniocular

• Binocular

• Onset:

• Recent onset squint manifested with

• Diplopia

• Past pointing

• Vertigo

• Prostration

• Diplopia:

• Diplopia may not be complained of in case of

adoption of head posture

• Or,when sensory adaptation occurs.

• Decompensation of pre existing heterophoria-

diplopia of intermittent onset.

• Recent onset acquired squint-sudden onset

diplopia.

• Type of diplopia-horizontal,cyclovertical

• Direction of gaze in which it predominant

• Whatever BSV is retained

Cosmetic defects:

• Whether the defect is Intermittent or constant

• Whether unilateral or alternating

• Head Posture.

Precipitating factor:like injury,illness,shock.

Past medical history

• Developmental history (children with cerebral palsy)

• H/O glass-

Regularity of use

Power of the glass

Proper cycloplegia for correction for his age.

• Use of prisms/convergence exercise/occlusion

• Surgery for squint

One or both eye

Which muscle

How much

What Sx.

Birth History

• Antenatal history-drugs taken/illness during pregnancy

• Gestational age & birth weight at delivery

• Type and length/problem during labour.

Family history

A. Visual Acuity:

a) In Preverbal Children-

• Fixation and following

• Comparison between behavior of the two eyes.

• Fixation Behavior

• 10∆ test

• Rotation test

• Preferential looking

a) Teller Acuity cards

b) Cardiff Acuity cards

• VEP

b) Verbal children:

• 2 years:picture naming (crowded Kay picture)

•

• 3 years:matching the letter optotypes (Keelaer logMar)

• B.Refraction

• C.Examination of Anterior and Posterior chamber

Lid problems,ptosis,media opacities

Pupillary reflexes

Fundus

1. Synoptophore

2. TNO test:480-15 sec of arc

3. Frisby:600-15 sec of arc

4. Lang:200-1200 sec of arc

1. Head posture:

• To be noted when pt is unconcious about it.

• Eye is out of the field of action.

2. Ocular Deviation

• By ordinary mm scale

• Synoptophore

• What to see?

Direction

Frequency

Magnitude

Comitancy

Laterality

AC/A ratio

A. Cover Tests:

• Prerequisites:

Ability to fixate the target

Have central fixation

No gross/severe mobility defects

a. Alternate Cover

b. Cover uncover test

c. Prism Bar Cover tests

a

b

• Cover Uncover test for tropia:

• Prism Bar Cover test

A. Hirschberg test:

B. Krimsky test

• A pen-torch is shone into the eyes

from arm’s length and the patient

asked to fixate the light.

• The distance of the corneal light

reflection from the centre of the pupil

is noted; each mm of deviation is

approximately equal to 7° (one

degree ≈ 2 prism dioptres).

placement of prisms in front of the

fixating eye until the corneal light

reflections are symmetrical

Hirschberg test

No obvious squint Manifest squint

Cover test(either eye) Cover test(fixing eye)

Other eye moves for

fixation

No movement

Remove cover

Squint remains

momentarily then aligned

Intermittent

Cover other eye

No movement Movement

fellow eye

Uncover test

Cover eye straighten No movement

Immediate: latent Sometime:intermittentAlternate cover

Latent/intermitent

No movement

Microtropia

Next slide

• Cover Test(fixing eye)

Other eye remain deviated

1. Blind eye

2. Eccentric fixation

3. Immobile

4. Pseudosquint

Other eye moves for fixation

Remove cover

Eye deviate again Eye remain straight,other eye

deviates

Manifest constant squint

Manifest alternating squint

1. Epicanthic folds-

esotropia

2. Abnormal interpupillary

distance-

short:esotropia

wide:exotropia

3. Angle kappa

Positive:exotropia

Negative:fovea is situated

nasal to the posterior pole

(high myopia and ectopic

fovea):esotropia

A. Maddox wing test

• Maddox rod test:

• Maddox Double Prism

Used in case of cyclodeviation

• Two prism of 4pd

• Pt looks at a horizontal

line (other eye ocluded)

two lines,parellal but

shifted vertically from

each other.

• Pt opens other eye (not

have double prism)

Line in between above

two lines.

• Versions towards the eight eccentric positions of gaze

are tested by asking the patient to follow a target.

• A quick cover test is performed in each position of gaze

to confirm whether a phoria has become a tropia or the

angle has increased and the patient is questioned

regarding diplopia.

• Ductions are assessed if reduced ocular motility is noted

in either or both eyes.

• The fellow eye is occluded and the patient asked to

follow the torch into various positions of gaze.

• Adduction:

• Normal-if nasal 1.3rd of the cornea

crosses the lower punctum

• Abduction:

• Normal-if temporal limbus touches

the lateral canthus.

• Oblique overaction-

• Angle of adducting eye makes

with horizontal line as it

elevates,abducts on lateral

version to opposite side.

RAF Rule

• It determines the capability of the motor system to cope

with an induced misalignment of visual axes.If it is

large,even a large angle squint remains latent.

• They may be tested with prisms bars or the

synoptophore.

• An increasingly strong prism is placed in front of one

eye, which will then abduct or adduct (depending on

whether the prism is base-in or base-out), in order to

maintain bifoveal fixation. When a prism greater than the

fusional amplitude is reached, diplopia is reported or one

eye drifts the other way, indicating the limit of vergence

ability.

A. Test for supression-

a) Worth 4 dot test:

• Four dots-NRC/HARC

• Five Dots-

Esodeviation-uncrossed

(red on right)

Exodeviation-crossed

(red on left)

Vertical-vertically displaced

• Three green Dots-Supression

of Rt.eye.

• Two red dots-Supression of

left eye.

b. Bagalini’s striated glass

test:

Symetrical cross-NRC or ARC of

Harmonious type

Asymetrical Cross-incomitant squint

with NRC

Single line-supression of the other eye

Cross with gap-central supression

scotoma

• C.4∆ Prism test:

In bifoveal fixation In Microtropia

• D.After Image Testing:

Flash-

horizontal-RE

Vertical-LE

Response:

1. Cross-NRC(irrespective

of deviation)

2. Asymmetrical crossing-

ARC

• Amount of separation

depends on angle of

anomaly.

A. Past Pointing:

• Diplopia charting:

• Image is

separated by red

green glass.

• To quantify the

separation

between the

double image

• Maximum

separation-field of

action of paralytic

muscle

• Hess/Lees charting:

• Anaesthesia

• Supine position

• Lids retracted

• Pt is asked to look in the

direction of the muscle being

tested (to relax antagonist)

• Eye is held in the limbus

• Rotated in the direction of

action of the muscle

Moves freely-negative

Restricted-positive

Push posteriorly-false +ve for

recti,desired for obliques.

• 1.Assess which eye is hypertropic in primary position.

2.Any increase in hypertropia in horizontal gaze

3.Bielschowsky Head tilt test:to see if any

increase of hypertropia on tilting of head to any

side