Grand Rounds

NATURE AND MANAGEMENT OF COMITANT CONVERGENT STRABISMUS Before dealing with specific types of strabismus, there are general factors that must be considered when assessing the suitability for treatment, which apply to all cases regardless of the condition.

Before dealing with specific types of strabismus, there are general factors that must be considered when assessing the suitability for treatment, which apply to all cases regardless of the condition.

Evaluation Age Age at onset Type of strabismus Angle of strabismus Depth of sensory adaptations Cooperation of patient and parent

Age

Age at onset

Type of strabismus

Angle of strabismus

Depth of sensory adaptations

Cooperation of patient and parent

Age under 4 years – no co-operation for exercises: Rx and occlusion possible only Over 8-9 years – not possible to restore BSV: cosmetic treatment only Most adults have come to terms with the strabismus and require refraction only. Some may want cosmetic surgery.

under 4 years – no co-operation for exercises: Rx and occlusion possible only

Over 8-9 years – not possible to restore BSV: cosmetic treatment only

Most adults have come to terms with the strabismus and require refraction only. Some may want cosmetic surgery.

Age at Onset this is critical (may have to refer to old photos) especially important to establish if the onset was within the first year (Px is more likely to have eccentric fixation, DVD, latent nystagmus) Next establish if onset is within the first 3 years Significance? : the younger the Px is at onset and the longer time to presentation, the worse the prognosis. NB May never have developed binocularly driven cells and therefore cannot expect to obtain BV If very recent onset the Px is more likely to have distressing symptoms and may require immediate referral (esp. if incomitant)

this is critical (may have to refer to old photos)

especially important to establish if the onset was within the first year (Px is more likely to have eccentric fixation, DVD, latent nystagmus)

Next establish if onset is within the first 3 years

Significance? : the younger the Px is at onset and the longer time to presentation, the worse the prognosis.

NB May never have developed binocularly driven cells and therefore cannot expect to obtain BV

If very recent onset the Px is more likely to have distressing symptoms and may require immediate referral (esp. if incomitant)

Type of Strabismus : some Pxs respond better to refractive/orthoptic treatment than others different methods of treatment are more appropriate for different types.

some Pxs respond better to refractive/orthoptic treatment than others

different methods of treatment are more appropriate for different types.

Angle of Strabismus the greater the angle the worse the prognosis >20∆ - surgery indicated 15-20∆ - other factors must be favourable for orthoptics <15∆ - good for orthoptics <6∆ - microtropia, no orthoptics necessary

the greater the angle the worse the prognosis

>20∆ - surgery indicated

15-20∆ - other factors must be favourable for orthoptics

<15∆ - good for orthoptics

<6∆ - microtropia, no orthoptics necessary

Depth of Sensory Adaptations the deeper, the worse the prognosis

the deeper, the worse the prognosis

Cooperation of Patient and Parent must have high levels of interest and perseverance and reasonable intelligence. Parents must give time for supervision of exercises

must have high levels of interest and perseverance and reasonable intelligence.

Parents must give time for supervision of exercises

Refractive Esotropias Fully accommodative esotropia Partially accommodative esotropia Convergence excess

Fully accommodative esotropia

Partially accommodative esotropia

Convergence excess

Fully Accommodative Esotropia Deviation is secondary to the presence of hyperopia Excessive accommodation for distance and near stimulates excessive convergence sufficient to cause a strabismus Onset usually 2-5 years; coincident with the increased use of accommodative effort AC/A ratio is usually normal BSV present in nearly all cases; may have microtropia if anisohyperopic Usually no or only slight amblyopia, unless strabismus is present for a long time

Deviation is secondary to the presence of hyperopia

Excessive accommodation for distance and near stimulates excessive convergence sufficient to cause a strabismus

Onset usually 2-5 years; coincident with the increased use of accommodative effort

AC/A ratio is usually normal

BSV present in nearly all cases; may have microtropia if anisohyperopic

Usually no or only slight amblyopia, unless strabismus is present for a long time

Management Correction of refractive error full cycloplegic Rx for constant wear Review 3-4 weeks later Check that no more latent hyperopia has become manifest and alter Rx is big difference Check state of BV and microtropia if aniso. Treat any suppression still present (simultaneous vision cards on the Holmes stereoscope; bar reading; appreciation of physiological diplopia)

Correction of refractive error

full cycloplegic Rx for constant wear

Review 3-4 weeks later

Check that no more latent hyperopia has become manifest and alter Rx is big difference

Check state of BV and microtropia if aniso.

Treat any suppression still present (simultaneous vision cards on the Holmes stereoscope; bar reading; appreciation of physiological diplopia)

Management If amblyopia worse than 6/12, may require period of direct part-time occlusion if under 7 years. NB if microtropia present, VA will never be equal NB Often a refractive error is all that is necessary Carefully selected Pxs may be able to remove Rx for sports or social events etc and can be helped to gain BSV without Rx by orthoptics

If amblyopia worse than 6/12, may require period of direct part-time occlusion if under 7 years. NB if microtropia present, VA will never be equal

NB Often a refractive error is all that is necessary

Carefully selected Pxs may be able to remove Rx for sports or social events etc and can be helped to gain BSV without Rx by orthoptics

Criteria: hyperopia < 4.00DS Astigmatism < 1.00DC Cooperation – Px should be of reading age (7 ish) Motivation – older children are best as they are more self-conscious regarding specs Parent’s cooperation is also essential. Warn that the Px will still need Rx at least for closework

hyperopia < 4.00DS

Astigmatism < 1.00DC

Cooperation – Px should be of reading age (7 ish)

Motivation – older children are best as they are more self-conscious regarding specs

Parent’s cooperation is also essential. Warn that the Px will still need Rx at least for closework

Method (i) teach Px recognition of pathological diplopia (eg coloured filters & spotlight, with or without vertical prism or CT to reveal other image) or train to stop accommodating (make the image go blurred) For many control of esotropia will occur spontaneously after (i).

(i) teach Px recognition of pathological diplopia (eg coloured filters & spotlight, with or without vertical prism or CT to reveal other image) or train to stop accommodating (make the image go blurred) For many control of esotropia will occur spontaneously after (i).

Method If not: (ii) Obtain BSV at intersection of visual axis and extend this area. Exercise fusional ranges (esp negative). Practice at home. (iii) Improvement of binocular VA without Rx by increasing negative relative convergence (difficult) eg bar reading whilst gradually reducing the Rx and print size; -ve lenses whist watching TV (take care to maintain BSV and not suppression); stereoscope; miotics for 3-4 weeks (HES; dual action) NB Most hospital departments want to see all fully accommodative strabismics. Any treatment should be taken cautiously and preferably in liaison with the HES.

If not: (ii) Obtain BSV at intersection of visual axis and extend this area. Exercise fusional ranges (esp negative). Practice at home.

(iii) Improvement of binocular VA without Rx by increasing negative relative convergence (difficult) eg bar reading whilst gradually reducing the Rx and print size; -ve lenses whist watching TV (take care to maintain BSV and not suppression); stereoscope; miotics for 3-4 weeks (HES; dual action)

NB Most hospital departments want to see all fully accommodative strabismics. Any treatment should be taken cautiously and preferably in liaison with the HES.

Partially Accommodative Esotropia Constant deviation but increases with accommodative effort Associated with hyperopia but residual angle still present with when corrected Usually amblyopia Onset 1-3 years; insidious BSV depends on the age of onset; usually not present Associated vertical deviation common (IO overaction of one or both eyes)

Constant deviation but increases with accommodative effort

Associated with hyperopia but residual angle still present with when corrected

Usually amblyopia

Onset 1-3 years; insidious

BSV depends on the age of onset; usually not present

Associated vertical deviation common (IO overaction of one or both eyes)

Management depends on the size of the residual angle. Referral is likely in most cases Full cycloplegic result given Treat any amblyopia by occlusion Re-inforcement and extension of BV – if it can be found to exist where the visual axes cross Introduce objects closer than and further than object of fixation to try to get Px to appreciate physiological diplopia – gradually move object in towards fixation object to overcome suppression, maintaining physiological diplopia

depends on the size of the residual angle.

Referral is likely in most cases

Full cycloplegic result given

Treat any amblyopia by occlusion

Re-inforcement and extension of BV – if it can be found to exist where the visual axes cross

Introduce objects closer than and further than object of fixation to try to get Px to appreciate physiological diplopia – gradually move object in towards fixation object to overcome suppression, maintaining physiological diplopia

Management bar reading at fixation distance where axes cross if above obtained easily , try to move point of fixation to reduce angle of deviation Refer for surgeons opinion:- for functional result if BSV demonstrated; otherwise cosmetic

bar reading at fixation distance where axes cross

if above obtained easily , try to move point of fixation to reduce angle of deviation

Refer for surgeons opinion:- for functional result if BSV demonstrated; otherwise cosmetic

Convergence Excess High AC/A ratio (>6:1) Strabismus at near only OR angle much greater at near Strabismus may only be present when looking at fine detail Onset 2-5 years, occasionally earlier Most have BSV, some microtropia Amblyopia rare (except in anisometropia) Most hyperopic but some are emmetropic or even myopic. It is important to differentiate convergence excess from non-accommodative near SOT (has normal AC/A ratio) and undercorrected hyperopia ( eg do cycloplegic).

High AC/A ratio (>6:1)

Strabismus at near only OR angle much greater at near

Strabismus may only be present when looking at fine detail

Onset 2-5 years, occasionally earlier

Most have BSV, some microtropia

Amblyopia rare (except in anisometropia)

Most hyperopic but some are emmetropic or even myopic.

It is important to differentiate convergence excess from non-accommodative near SOT (has normal AC/A ratio) and undercorrected hyperopia ( eg do cycloplegic).

Management Depends on the AC/A ratio If >8-10∆/D, unlikely to respond conservatively Also if near deviation is >25 - 30∆, refer for surgery

Depends on the AC/A ratio

If >8-10∆/D, unlikely to respond conservatively

Also if near deviation is >25 - 30∆, refer for surgery

Management Otherwise: correction of refractive error – full cycloplegic Rx, unless Px is myopic then give a slight undercorrection amblyopia treatment (if necessary) by PT occlusion Bifocal spectacles – find an add that eliminates near deviation (by CT) enabling PX to maintain comfortable BSV with adequate binocular VA for all near activities Start with +1.00 Add and increase in 0.50 steps Try Fresnels on one month trial Give large flat top seg set high bisecting pupil Carefully fit and give full instructions Gradually reduce add in time and discard if possible Use a bar reader to establish BSV Problem: dependency on add by young adults, poor fitting and compliance by children and wear and tear

Otherwise:

correction of refractive error – full cycloplegic Rx, unless Px is myopic then give a slight undercorrection

amblyopia treatment (if necessary) by PT occlusion

Bifocal spectacles – find an add that eliminates near deviation (by CT) enabling PX to maintain comfortable BSV with adequate binocular VA for all near activities

Start with +1.00 Add and increase in 0.50 steps

Try Fresnels on one month trial

Give large flat top seg set high bisecting pupil

Carefully fit and give full instructions

Gradually reduce add in time and discard if possible

Use a bar reader to establish BSV

Problem: dependency on add by young adults, poor fitting and compliance by children and wear and tear

Management Contact Lenses – Calcutt (1984) reported that CLs (sometimes with extra +1.00D) reduced the angle by up to 15∆, often producing a latent deviation and useful BSV. Needs further trials Miotic drugs – combined with orthoptics (particularly good for 2-5 year olds whose cooperation is poor for other methods. Use over a period of weeks) Orthoptics for use without the Rx – minority of Pxs > 6 years; good cooperation and small deviations Antisuppression treatment

Contact Lenses – Calcutt (1984) reported that CLs (sometimes with extra +1.00D) reduced the angle by up to 15∆, often producing a latent deviation and useful BSV. Needs further trials

Miotic drugs – combined with orthoptics (particularly good for 2-5 year olds whose cooperation is poor for other methods. Use over a period of weeks)

Orthoptics for use without the Rx – minority of Pxs > 6 years; good cooperation and small deviations

Antisuppression treatment

Management Control of deviation by extending area of BSV – move target closer Increase binocular VA – increase –ve fusional reserves (usually needs some optical correction to achieve) Of minimal value on its own but can be useful in conjunction with other treatment or surgery Surgery – especially where the prognosis is poor for orthoptics or other methods have failed

Control of deviation by extending area of BSV – move target closer

Increase binocular VA – increase –ve fusional reserves (usually needs some optical correction to achieve)

Of minimal value on its own but can be useful in conjunction with other treatment or surgery

Surgery – especially where the prognosis is poor for orthoptics or other methods have failed

Non-refractive Esotropias

Constant: Onset 1-2 years Strabismic amblyopia common Often have an associated vertical deviation

Onset 1-2 years

Strabismic amblyopia common

Often have an associated vertical deviation

Intermittent:

Near esotropia Ortho or small SOP on distance fixation Moderate/large SOT for near No amblyopia Often no significant refractive error Normal or low AC/A ratio Normal near point of accommodation No reduction in angle with plus lenses Normal sensory and motor fusion Thought to be due to high proximal convergence or high tonic convergence

Ortho or small SOP on distance fixation

Moderate/large SOT for near

No amblyopia

Often no significant refractive error

Normal or low AC/A ratio

Normal near point of accommodation

No reduction in angle with plus lenses

Normal sensory and motor fusion

Thought to be due to high proximal convergence or high tonic convergence

Distance Esotropia Rare SOT for distance, SOP for near No significant refractive error VA normal and equal Full ocular movements (differentiates 6 th nerve palsy or dysthyroid eye disease)

Rare

SOT for distance, SOP for near

No significant refractive error

VA normal and equal

Full ocular movements (differentiates 6 th nerve palsy or dysthyroid eye disease)

Cyclic Esotropia Esotropia occurring at regular intervals of time, BSV at others Usual pattern = 24 hrs SOT/ 24 hrs BSV = “alternate day strabismus” Onset 4-5 years or older Most emmetropic with equal VAs Diplopia rare Gradually becomes constant - then surgery can be considered Often associated with a psychogenic disturbance

Esotropia occurring at regular intervals of time, BSV at others

Usual pattern = 24 hrs SOT/ 24 hrs BSV = “alternate day strabismus”

Onset 4-5 years or older

Most emmetropic with equal VAs

Diplopia rare

Gradually becomes constant - then surgery can be considered

Often associated with a psychogenic disturbance

Consecutive Esotropia Spontaneous – following XOT (rare – occurs with DVD) Post-operative – following overcorrection of an XOT

Spontaneous – following XOT (rare – occurs with DVD)

Post-operative – following overcorrection of an XOT

Symptomatic (secondary) esotropia Following severe visual loss in childhood, due to muscle tonus

Following severe visual loss in childhood, due to muscle tonus

The management of non-refractive SOT is almost always surgical. Can try prism for distance SOT where angle < 10 ∆ (Use Fresnel lens initially – adaptation) Correct the refractive error to remove any astenopia (independent of the deviation) Any amblyopia must be treated.

Can try prism for distance SOT where angle < 10 ∆ (Use Fresnel lens initially – adaptation)

Correct the refractive error to remove any astenopia (independent of the deviation)

Any amblyopia must be treated.

Essential Infantile Esotropia Occurs before 6 months (usually 3-6 months) Usually large angle (>40 ∆) Same angle distance and near Crossed alternating fixation Less than half have ambyopia with EF (Dale, 1982) May have latent nystagmus Sometimes have DVD Looks like a bilateral LR palsy (distinguish by “dolls head” movement)

Occurs before 6 months (usually 3-6 months)

Usually large angle (>40 ∆)

Same angle distance and near

Crossed alternating fixation

Less than half have ambyopia with EF (Dale, 1982)

May have latent nystagmus

Sometimes have DVD

Looks like a bilateral LR palsy (distinguish by “dolls head” movement)

Nystagmus Blocking (or compensation) Syndrome Convergent strabismus is adopted to lessen the nystagmoid movements which are reduced on convergence of the eyes Pxs head usually turned away from side of fixing eye – produces greater convergence of this eye.

Convergent strabismus is adopted to lessen the nystagmoid movements which are reduced on convergence of the eyes

Pxs head usually turned away from side of fixing eye – produces greater convergence of this eye.

Accommodative Infantile Esotropia Rare Most are hyperopic Half have a high AC/A ratio BV weak and unstable compared with later onset accommodative strabismus Strabismic amblyopia

Rare

Most are hyperopic

Half have a high AC/A ratio

BV weak and unstable compared with later onset accommodative strabismus

Strabismic amblyopia

Sixth Nerve Palsy Rare in isolation, but can occur with neurological disorders eg hydrocephalus Can be caused by trauma in forceps delivery NONE OF THESE CONDITIONS CAN BE TREATED BY REFRACTIVE OR ORTHOPTIC TREATMENT ALONE : SURGICAL TREATMENT SHOULD BE SOUGHT AS SOON AS POSSIBLE

Rare in isolation, but can occur with neurological disorders eg hydrocephalus

Can be caused by trauma in forceps delivery NONE OF THESE CONDITIONS CAN BE TREATED BY REFRACTIVE OR ORTHOPTIC TREATMENT ALONE : SURGICAL TREATMENT SHOULD BE SOUGHT AS SOON AS POSSIBLE

Nature and Management of Comitant Divergent Strabismus

Divergence Excess Manifest for distance fixation only, usually intermittently but may be constant Most apparent during inattention, ill health and fatigue, after alcohol and in bright light Mostly females Little refractive error VA usually good and equal Usually no symptoms as the sensory adaptations are good Px may not have known about strabismus until told by others AC/A is normal in true, but high in pseudo-divergence excess

Manifest for distance fixation only, usually intermittently but may be constant

Most apparent during inattention, ill health and fatigue, after alcohol and in bright light

Mostly females

Little refractive error

VA usually good and equal

Usually no symptoms as the sensory adaptations are good

Px may not have known about strabismus until told by others

AC/A is normal in true, but high in pseudo-divergence excess

Management Correction of myopia or anisometropia Low degrees of hyperopia best left uncorrected Most require referral for surgery Where angle is <15∆ (rare – usually much larger) and BSV maintained most of the time, optical &/or orthoptic treatment may be of benefit – but usually only in the short term to delay surgery

Correction of myopia or anisometropia

Low degrees of hyperopia best left uncorrected

Most require referral for surgery

Where angle is <15∆ (rare – usually much larger) and BSV maintained most of the time, optical &/or orthoptic treatment may be of benefit – but usually only in the short term to delay surgery

Management Orthoptics : anti-suppression exercises (only if NRC) Exercise base out prism vergences Teach physiological diplopia (so Px knows when strabismic) Optical:negative lenses can be successful in the short term, where accommodation is good Prisms (full base in – then gradually reduce) – short term Tinted spectacles – useful in countries with high light intensity – again only short-term- high illumination has a dissociating effect in exodeviations – can cause suppression or closing of one eye PROBABLY BEST TO REFER FOR SURGERY FROM OUTSET

Orthoptics : anti-suppression exercises (only if NRC) Exercise base out prism vergences Teach physiological diplopia (so Px knows when strabismic)

Optical:negative lenses can be successful in the short term, where accommodation is good

Prisms (full base in – then gradually reduce) – short term

Tinted spectacles – useful in countries with high light intensity – again only short-term- high illumination has a dissociating effect in exodeviations – can cause suppression or closing of one eye PROBABLY BEST TO REFER FOR SURGERY FROM OUTSET

Near Exophoria (Convergence Insufficiency) Most commonly occurs in the mid-teens when reduced convergence &/or increased myopia break down the BV, can be in adults Rarely occurs at around 5-7 years old with an accommodative element – usually low AC/A Typically XOP at distance XOT at near Pxs present with symptoms (diplopia, astenopia) Usually equal VAs, poor or no convergence, NRC and normal sensory fusion with poor positive fusional amplitude Often myopic

Most commonly occurs in the mid-teens when reduced convergence &/or increased myopia break down the BV, can be in adults

Rarely occurs at around 5-7 years old with an accommodative element – usually low AC/A

Typically XOP at distance XOT at near

Pxs present with symptoms (diplopia, astenopia)

Usually equal VAs, poor or no convergence, NRC and normal sensory fusion with poor positive fusional amplitude

Often myopic

Management If strabismus is constantly manifest for near and angle >25∆ - refer For smaller angles and only occasionally manifest: Correct any myopia (this may be enough to make deviation latent) Orthoptics – exercise base out prism vergences (often successful) Prisms – base In just sufficient to enable BSV for near (Usually tolerated for distance) gradually reduce the strength of the prism and combine with orthoptics Occasionally try negative adds If no improvement – refer for surgery.

If strabismus is constantly manifest for near and angle >25∆ - refer

For smaller angles and only occasionally manifest:

Correct any myopia (this may be enough to make deviation latent)

Orthoptics – exercise base out prism vergences (often successful)

Prisms – base In just sufficient to enable BSV for near (Usually tolerated for distance)

gradually reduce the strength of the prism and combine with orthoptics

Occasionally try negative adds

If no improvement – refer for surgery.

Constant (Basic) Exotropia Constant divergent strabismus, equal angles distance and near Onset in early childhood: no symptoms, no sensory fusion Closure of one eye in bright light Often alternating, with equal VAs; homonymous fixation

Constant divergent strabismus, equal angles distance and near

Onset in early childhood: no symptoms, no sensory fusion

Closure of one eye in bright light

Often alternating, with equal VAs; homonymous fixation

Management Surgical correction for cosmetic (or occasionally functional) result Occasionally in children <7 years old – try –ve additions to eliminate strabismus on the CT in conjunction with exercises to establish BSV. Gradually try to phase out the –ve add over several years. If a divergent strabismus has a vertical component – orthoptics not successful

Surgical correction for cosmetic (or occasionally functional) result

Occasionally in children <7 years old – try –ve additions to eliminate strabismus on the CT in conjunction with exercises to establish BSV.

Gradually try to phase out the –ve add over several years.

If a divergent strabismus has a vertical component – orthoptics not successful

Consectutive Exotropia Spontaneous – usually occurs following early onset partially accommodative esotropia with a high degree of hyperopia. Develops as the amplitude of accommodation decreases, or precipitated by the late correction of hyperopia Post-operatively – usually several years after surgical correction of accommodative SOT – especially if hyperopic correction is now prescribed

Spontaneous – usually occurs following early onset partially accommodative esotropia with a high degree of hyperopia.

Develops as the amplitude of accommodation decreases, or precipitated by the late correction of hyperopia

Post-operatively – usually several years after surgical correction of accommodative SOT – especially if hyperopic correction is now prescribed

Management Partial correction of hyperopia + Base out prism vergence exercises sometimes helps Remedial surgery

Partial correction of hyperopia + Base out prism

vergence exercises sometimes helps

Remedial surgery

Symptomatic (Secondary) Exotropia Due to severe loss of vision in one eye in adult life Management = Cosmetic surgery

Due to severe loss of vision in one eye in adult life

Management = Cosmetic surgery

Onset of Exotropia before 1 year old Usually symptomatic (or secondary) due to visual loss from birth Rarely congenital exotropia, often with nystagmus and DVD Management No optometric treatment - refer

Usually symptomatic (or secondary) due to visual loss from birth

Rarely congenital exotropia, often with nystagmus and DVD

Management

No optometric treatment - refer

Vertical Heterophoria Hyperphoria a potential deviation of one eye upwards which becomes an actual deviation when the two eyes are dissociated and recovers when the dissociating factors are removed 15-30% patients have a measureable hyperphoria (not necessarily decompensated).

a potential deviation of one eye upwards which becomes an actual deviation when the two eyes are dissociated and recovers when the dissociating factors are removed

15-30% patients have a measureable hyperphoria (not necessarily decompensated).

Two types Secondary Primary

Secondary

Primary

Secondary hyperphoria Horizontal heterophoria Incomitant deviations Tilted spectacles

Horizontal heterophoria

Incomitant deviations

Tilted spectacles

Primary/True hyperphoria – seldom >3  is considered largely due to slight anatomical misalignment of the eyes or orbits or muscle insertions for which there is physiological compensation

seldom >3 

is considered largely due to slight anatomical misalignment of the eyes or orbits or muscle insertions for which there is physiological compensation

Investigation

Symptoms Marked with low degrees Frontal HA’s; pain, soreness of lid margins Head tilt alleviates symptoms Prefers monocular vision Motility - Evaluate carefully to ensure there is no paresis Refraction – very important to assess binocular balancing, and check if both images are aligned (Mallett units are useful for this or infinity balance techniques).

Marked with low degrees

Frontal HA’s; pain, soreness of lid margins

Head tilt alleviates symptoms

Prefers monocular vision

Motility - Evaluate carefully to ensure there is no paresis

Refraction – very important to assess binocular balancing, and check if both images are aligned (Mallett units are useful for this or infinity balance techniques).

Management Remove cause of decompensation ie pay attention to working conditions, any stress or ill health of the patient RE: Rx may alleviate symptoms anisometropia – take care to prevent vertical problems. Orthoptics: if associated with horizontal phoria, development of horizontal fusional reserves may result in the vertical phoria becoming compensated. Prisms: perhaps best method of treatment especially for primary vertical hyperphoria. The minimum amount of prism should be prescribed and the prism should be divided between the two eyes or the maximum prism is placed before the non-dominant eye. Surgery: May be necessary in high hyperphoria or Incomitancy Truly comitant hyperdeviations are rare.

Remove cause of decompensation ie pay attention to working conditions, any stress or ill health of the patient

RE: Rx may alleviate symptoms anisometropia – take care to prevent vertical problems.

Orthoptics: if associated with horizontal phoria, development of horizontal fusional reserves may result in the vertical phoria becoming compensated.

Prisms: perhaps best method of treatment especially for primary vertical hyperphoria. The minimum amount of prism should be prescribed and the prism should be divided between the two eyes or the maximum prism is placed before the non-dominant eye.

Surgery: May be necessary in high hyperphoria or Incomitancy

Truly comitant hyperdeviations are rare.

Dissociated Vertical Deviation (alternating sursumduction) Can be mistaken as a hyperphoria During CT the covered eye deviates slowly up to  25  Eye tends to extort on cover When cover is removed eye returns to fixation position Movement may not be equal between the eyes Can be accompanying cyclorotation Latent nystagmus is common associated finding Obscure No symptoms- no treatment If co-exists with another deviation, treatment appropriate to the other deviation is given if symptoms exist.

Can be mistaken as a hyperphoria

During CT the covered eye deviates slowly up to  25 

Eye tends to extort on cover

When cover is removed eye returns to fixation position

Movement may not be equal between the eyes

Can be accompanying cyclorotation

Latent nystagmus is common associated finding

Obscure

No symptoms- no treatment

If co-exists with another deviation, treatment appropriate to the other deviation is given if symptoms exist.

Dissociated Vertical Deviation (alternating sursumduction) Stidwell, 1997

A and V Patterns These deviations show variations in horizontal magnitude as the fixation point moves up and down. may be associated with convergence or divergence and occur in both heterotropia and heterophoria.

These deviations show variations in horizontal magnitude as the fixation point moves up and down.

may be associated with convergence or divergence and occur in both heterotropia and heterophoria.

Convergence A pattern Increased convergence on elevation Decreased convergence on depression V pattern increased convergence on depression decreased convergence on elevation

A pattern Increased convergence on elevation Decreased convergence on depression

V pattern increased convergence on depression decreased convergence on elevation

Divergence A pattern increased divergence on depression decreased divergence on elevation V Pattern -increased divergence on elevation decreased divergence on depression

A pattern increased divergence on depression decreased divergence on elevation

V Pattern -increased divergence on elevation decreased divergence on depression

The aetiology of A and V patterns is not agreed and may vary between individuals although over- and under-action of the oblique muscles appears to be the most likely cause. It is thought that bilateral inferior oblique overaction produces a V pattern in both eso and exo deviations; and bilateral superior oblique overactions produces the A pattern.

is not agreed and may vary between individuals although over- and under-action of the oblique muscles appears to be the most likely cause.

It is thought that bilateral inferior oblique overaction produces a V pattern in both eso and exo deviations; and bilateral superior oblique overactions produces the A pattern.

Cyclodeviations Incidence not known Usually caused by an imbalance between the muscle pair affecting intorsion (SO and SR) and the muscle pair inducing extorsion (IO and IR ). Doubtful if cyclophoria exists as a primary cyclophoria although authorities give methods for its detection.

Incidence not known

Usually caused by an imbalance between the muscle pair affecting intorsion (SO and SR) and the muscle pair inducing extorsion (IO and IR ).

Doubtful if cyclophoria exists as a primary cyclophoria although authorities give methods for its detection.

Pseudostrabismus Epicanthus in infants can be more or less pronounced. Epicanthus can obscure the inner canthus giving rise to the appearance of esotropia when none is present. In time epicanthal fold usually disappears with the development of the bridge of the nose Other examples of pseudostrabismus include facial asymmetry failure of the optical (centres of the cornea and lens) and visual axis (fovea to fixation point) to coincide

Epicanthus in infants can be more or less pronounced.

Epicanthus can obscure the inner canthus giving rise to the appearance of esotropia when none is present.

In time epicanthal fold usually disappears with the development of the bridge of the nose

Other examples of pseudostrabismus include

facial asymmetry

failure of the optical (centres of the cornea and lens) and visual axis (fovea to fixation point) to coincide