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Basics of Strabismus testing

Laura May, CO

Madison Kincade

http://www.allaboutvision.com/conditions/strabismus.htm

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Strabismus

• Strabismus is any misalignment of the eyes

• Estimated that 4% of the U.S. population has strabismus

• Commonly described by the direction of deviation

• Can be described by cause of strabismus

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Types of Strabismus

• Esotropia = ET

– E(T), E

• Exotropia = XT

– X(T), X

• Hypertropia = HT

– H(T), H

• Dissociated Vertical Deviation = DVD

• Measurements at near use ‘ symbol

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Testing Techniques

http://www.guldenophthalmics.com/products/index.php/occluder-short-handle-black.html

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Cover tests

• Cover-uncover test

• Alternate prism cover test

• Simultaneous prism cover test

• Patch test (Marlowe)

https://ohioamblyoperegistry.com/about/

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Cover Test

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Uncover Test

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Alternate Prism Cover Test

25 PD

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Alternate Prism Cover Test

30 PD

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Simultaneous Prism Cover Test

6 PD

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Simultaneous Prism Cover Test

10 PD

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Estimation Techniques

• Hirschberg

• Krimsky

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Angle Kappa

• The angle between the visual axis and the pupillary axis

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Motor fusion

• Types and normal ranges – Convergence

• Near: 35-40 pd

• Distance: 20-25 pd

– Divergence • Near: 15pd

• Distance: 7pd

– Vertical vergence • 2-3 pd (base up/down)

– Cyclovergence • 1-2 degrees

http://www.guldenophthalmics.com/products/index.php/prisms/bv-15-b-16-set.html

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Vergences

Simultaneous control of eyes in opposite direction Convergence

1. Tonic – constant innervation tone to the EOM while awake 2. Accommodative – near reflex, near triad 3. Fusional – stimulus to maintain clear, single image 4. Relative – amount of BO prism person can handle 5. Proximal – controlled by awareness of near 6. Voluntary – ability of eyes to converge without stimulus

Divergence 1. Tonic 2. Fusional 3. Relative

Vertical 1. Tonic 2. Fusional

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NPC/NPA

• Near point of convergence (NPC)

– Accommodative target moved towards patient’s nose, break point recorded when patient becomes XT

– 10cm or less = normal

• Near point of Accommodation

– Prince rule used to measure

– Tested monocular and binocularly

http://www.west-op.com/berensaccommod.html

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Binocular Vision

• Worth 4 dot

– SBV

– Suppression

– Diplopia

• Titmus Fly

– Stereo

– Monocular clues

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Bagolini Striated Lenses

• Bagolini lenses test for:

– Diplopia (ET/XT)

– Fusion or Harmonious ARC

– Suppression Scotoma

– Suppression

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Detection and measure cyclotropia

• Double maddox rods

• Synoptophore

• Bagolini lens

• Fundus photography

http://www.ophthalworld.de/lshop,showdetail,2004g,en,,vorhalter_und_leisten.neue_vorhalter_und_leisten,01130,8,Tshowrub--vorhalter_und_leisten.neue_vorhalter_und_leisten,.htm

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Diplopia

• Testing in clinic

• Monocular vs. Binocular

• Treatments

– Fresnel prism/ground in prism

– Fogging/occlusion

http://www.medicalnewstoday.com/articles/170634.php

http://www.eyecareandcure.com/ECC-Products/Occluders-Maddox-Rods

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AC/A ratio

• Gradient

• Heterophoria

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Prism adaptation test

• Uses

– Determine position of motor stability with acquired ET

– Determine fusion potential

– Determine risk of surgical over-correction

http://www.eyecareandcure.com.sg/fresnel-presson-prism35d-pi-4243.html?image=0

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Extraocular Muscles

http://marineyes.com/anatomy/muscles.html

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Extraocular Muscles

• Agonist: primary muscle that is moving eye

• Antagonist: opposite muscle that is relaxing in the same eye

• Synergist: muscle helping the eye move along with the agonist – Ispilateral synergist: same eye

– Contralateral synergist: opposite eye – Yoke pair

• Contralateral Antagonist: opposite eye that antagonist of the yoke pair in that eye

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Extraocular Muscles

• Herring’s Law: innervation to the EOM generated by yoke pairs/contralateral synergist.

• Sherrington’s Law: reciprocal innervation.

• Listing’s Law: no torsion occurs

• Donder’s law: torsion is produced

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Yoke Muscles

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Extraocular Muscles Muscle Primary Action Secondary

Action Cranial Nerve Innervation

Lateral Rectus Abduction None 6th CN

Medial Rectus Adduction None 3rd CN

Superior Rectus Elevation Adduction, intorsion

3rd CN

Inferior Rectus Depression Adduction, extorsion

3rd CN

Superior Oblique Intorsion Depression, abduction

4th CN

Inferior Oblique Extorsion Elevation, abduction

3rd CN

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Cranial Nerve Palsies

Common causes of CN palsies Nerve Childhood Adult life > 55yr

3rd Trauma Intracranial aneurysm

Hypertension and diabetes

4th Trauma Trauma Trauma

6th Idiopathic, isolated benign, increased ICP, Trauma

MS, Space occupying lesion, Trauma

Hypertension, diabetes, space occupying lesion

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Ocular rotations

Ductions vs Versions

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Ductions Horizontal Ductions Vertical Ductions

Cyclo-Ductions

Primary

Adduction

Abduction

Supraduction

Infraduction

Excycloduction

Incycloduction

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Versions

Supraversion Levosupraversion Dextrosupraversion

Dextroversion Levoversion

Dextroinfraversion

Infraversion

Levoinfraversion

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Objective measurements

• Distance and near fixation

• Nine diagnostic positions of gaze

• Head tilts

• Three-step test

http://schorlab.berkeley.edu/passpro/oculomotor/assets/images/Fig5-8.gif

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Pattern Strabismus

• A-pattern

– Increasing ET or decreasing XT in up gaze

– Decreasing ET or increasing XT in down gaze

– A pattern must have 10 pd of incomitance

• V-pattern

– Increasing XT or decreasing ET in up gaze

– Decreasing XT or increasing ET in down gaze

– V pattern must have 15 pd of incomitance

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“VAVA”

• V-ET – most common

• A-ET – most common in patients with Down syndrome

• V-XT

• A-XT – least common

http://www.cyber-sight.org/bins/volume_page.asp?cid=735-2858-4397-4403-4604-4619

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Abnormal Head Postures Characteristics Ocular Non-ocular

Cover test Abnormal EOM Normal motility

Straighten head - Able to passively straighten head

- Longstanding AHP more difficult

Unable to passively straighten head

Occlusion When one eye occluded, head will straighten

When one eye occluded no change in AHP

Facial Asymmetry No or slight facial asymmetry

Marked facial asymmetry

Head position Turn and tilt vary depending on muscle affected

Tilt and turn to side of contracted sternocleidomastoid muscle

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Esotropia

http://www.pedseye.com/strabismus_esotropia.htm

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Esotropia Infantile Acquired

Congenital Accommodative Esotropia

Nystagmus blockage syndrome Non accommodative Esotropia

Ciancia Syndrome Acute comitant Esotropia

Duane’s Syndrome Cyclic Esotropia

Abducens palsy Sensory Esotropia

Moebius Syndrome Divergence Insufficiency

Divergence Paresis

Spasm of near reflex

Medial rectus restriction

Lateral rectus weakness

Consecutive and secondary Esotropia

Small angle Esotropia

Monofixation Syndrome

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Esotropia

• Classification – Age of onset

• Infantile

• Acquired

– Role of accommodation and refraction • Non-accommodative

• Refractive

• High accommodative convergence to accommodation ratio

• Partially accommodative

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Psuedoesotropia

• Prominent epicanthal folds

• Narrow interpupillary distance

• Negative angle kappa

• Enophthalmos

• Craniofacial malformations

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Congenital Esotropia

• Onset near birth

• Usually large angle > 30PD

• Associated vertical deviations common

• Latent nystagmus

• Cross fixation

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Accommodative Esotropia

• Onset age 6mo – 7yrs, average 2.5yrs

• Moderate to high hyperopia

• May be only partially accommodative

• May have a high AC/A

• Can be intermittent or variable

• May decompensate

http://webeye.ophth.uiowa.edu/eyeforum/cases/129-accommodative-esotropia.htm

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Duane’s Syndrome

• Congenital miswiring of LR muscle with the branches from the medial rectus subnucleus

• 3 clinical types

• PF changes

• Globe retraction

By Jmarchn - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20423772

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6th CN Palsy

• Signs and Symptoms

– Limitation in abduction

– Ductions > versions

– D ET > N ET’

– Face turn toward paretic eye

– ET larger in affected gaze

– Can be unilateral or bilateral

http://entokey.com/neuro-ophthalmology-6/

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Duane’s vs VI palsy

Clinical Characteristics Type 1 Duane's VI Nerve Palsy

Complete absence of abduction

Typical Not Always

Large ET in primary No Yes

Globe retraction in adduction

Yes No

Lid fissure widening on abduction

Yes Possible

Upshoot/downshoot Yes No

Diplopia Rare Yes

Greater ET at distance Rare Common

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Monofixation Syndrome

• Small manifest ET

• Central scotoma

– 4 BO test

• 4 BO prism held in front of either eye, watch for a shift and convergence

• Mild amblyopia common

• Reduced stereoacuity

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Exotropia

http://optometrist.com.au/exotropia/

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Exotropia

Infantile Acquired

Congenital exotropia Intermittent exotropia

Sensory exotropia Secondary or consecutive exotropia

Convergence insufficiency exotropia

Third nerve palsy

Duane syndrome type 2

Sensory exotropia

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Exotropia

• Classification

– Age of onset

• Infantile

• Acquired

– Distance-near relationship

• Basic (D=N)

• Divergence excess (D>N)

• Pseudo-divergence excess

• Convergence insufficiency (N>D)

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Pseduoexotropia

• Positive angle kappa

• Wide interpupillary distance

• Wide palpebral fissures

• Exophalmos

• Narrowing lateral canthi

• Hypertelorism

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Congenital Exotropia

• Onset by age 6 months

• Associated vertical deviations

• Large angle > 30pd

• Latent nystagmus

• May have associated neurological abnormalities

https://www.aapos.org/terms/conditions/49

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X(T)

• Broken down X

• Monocular lid closure

• Wider VF

• No diplopia

• Control

– Good, fair, poor

http://www.omicsgroup.org/journals/peripapillary-staphyloma-in-a-child-with-intermittent-exotropia-2165-7920.1000424.php?aid=33470

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Convergence insufficiency

• Characteristics

– Reduced convergence amplitudes

– May c/o headaches, asthenopia and eye strain

– May have intermittent diplopia

– May have reduced NPC

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Convergence insufficiency

• Treatments

– Pencil pushups

– Stereogram

– Computer orthoptics

– Prisms

http://computerorthoptics.com/

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3rd Cranial Nerve

• 3rd CN

– Superior division innervates

• Superior rectus

• Levator

– Inferior division innervates

• Inferior recuts

• Inferior oblique

• Medial rectus

• Intraocular muscles

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3rd CN Palsy

• Characteristics

– Ptosis

– Dilation of pupil

– Limitation of adduction, elevation and depression

– Exotropia and hypotropia in primary

– Accommodative weakness

– May present as isolated extraocular muscle palsy

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Vertical Strabismus

http://www.cehjournal.org/article/understanding-detecting-and-managing-strabismus/

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Vertical Strabismus

Paretic Muscle Restriction Other

SO palsy Brown syndrome DVD

IO palsy Monocular Elevation Deficiency

Myasthenia Gravis

SR palsy CPEO Skew Deviation

IR palsy Congenital fibrosis PSP

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4th CN Palsy

• Superior Oblique Palsy

– Hypertropia of affected eye

– AHP is common

– Excylotorison

– Positive Bielschowsky head tilt test

– Can be congenital or aquired

– Unilateral or bilateral

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4th CN Palsy

Congenital/long standing Acquired

Diplopia Rare Present, but can be limited to paretic field

Image tilting Absent Common

Comitance Spread may obscure paresis

Characteristically incomitant

Abnormal head posture May persist on covering eye due to contracture

Disappears on covering eye

Facial Asymmetry Common Absent

Past pointing Absent Present

Old photos May show AHP Negative

Amblyopia May be present Absent

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Unilateral vs Bilateral 4th

• Bilateral SO palsy

– V pattern present

– 10 degrees of excyclotorsion, may increase in downgaze

– Reversal of HT on side gazes, tilts or oblique fields

– ET maybe associated

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Bilateral 4th CN Palsy

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Parks–Bielschowsky three-step test

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Brown Syndrome

http://www.webhealthwatch.com/eye-disorders/treatment-and-care-of-brown-syndrome.html

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Brown Syndrome

• Inability to elevate in adduction

– Duction = version

• Hypotropia in primary and/or upgaze

• Divergence on upgaze, V pattern

• Etiology

– Congenital, traumatic, inflammatory, iatrogenic

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IO palsy

• Inferior division of 3rd CN , look for MR, IR and pupil involvement

• Test with 3 step test

• Overaction of ipsilateral SO

• AHP – turn to opposite side, tilt to affected side

• Differential dx = Brown’s syndrome

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Brown vs IO palsy

Clinical Characteristics Brown Syndrome IO Palsy

Limitation of elevation in adduction

Yes Yes

Overaction of ipsilateral SO No Yes

Versions = Ductions with elevation in adduction

Yes No

Positive forced ductions Yes No

Positive forced generations No Yes

Positive head tilt test No Yes

Pattern V A

Incyclotorsion No Yes

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DVD

• Up-drift of eye occurring under cover or spoontaneoulsy during visual inattentiveness

• Associated with:

– early disruption of binocular development

– Latent nystagmus

– Horizontal infantile strabismus

– Poor binocular VA

• No associated HypoT deviation

http://www.mattweedmd.com/news/

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Conclusion

• Types of strabismus

– Horizontal/vertical

– Dissociated deviations

• Testing techniques

– Cover tests

– Special testing

• EOM

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Questions?