10. Introduction to paralytic strabismus Flashcards
What is paralytic strabismus and what does it result in?
Meaning: Angle of deviation changes depending on gaze or depending on which eye is fixing.
Also known as incomitant deviation.
Cause of paralytic strabismus ?
Poor motility in 1 or both eyes
Paralytic strabismus - Congenital or acquired?
Both possible
What is RADSIN?
Recti ADduct, Superior INtort
How are versions tests?
When both eye are open- patients are asked to look at 9 different position of gazes.
Duction are bilateral movements- true or false?
False- ductions are bilateral
Dextro version VS Laevoversion?
Dexto- px asked to look right
Laeovo- px asked to look left
If an underaction is seen on versions, before making a diagnosis what is important?
It is important to check ductions as well before making a diagnosis.
3 classification of limited eye movement?
- Neurogenic- majority of the palsies.
- Mechanical
- Myogenic
What are neurogenic palsies?
What causes this?
Ductions greater than versions.
When underacting doesn’t move when both eyes are open. But when normal eye is covered, the underacting eye will get extra innervation and move.
Cause: Causes by lesions between nucleus and muscle
What are neurogenic intranuclears?
VI (abducens), UV (trochlear), III (Occulomotor)
What are mechanical palsies?
These are palsies that prevent free movement of the globe or interfere with muscle contraction and relaxation.
Examples of mechanical palsies?
Brown’s. Duanes. TES. Blow- out facture
What are myogenic palsies?
Palsies within the actual muscle that cause the problem. May involve individual extraocular muscles or a combination.
Examples of myogenic palsies?
Myasthenia Gravis, Myositis, TED (wet phase)
What are the 4 diagnose aims when investigating paralytic palsies?
- Identify if- neuro, mechanical or myogenic
- What muscles are affected?
- Congenital vs acquired?
- Possible causes?
Other than the 4 diagnose aims what other investigating paralytic palsies is needed- 4?
- Decide if referral is needed and how urgent.
- Treat symptoms if possible
- Document progress/ recovery
- Is it congenital or acquired? - congenital is a more worrying sign
AHP- Congenial vs acquired?
Congenial
Congenial vs acquired- in relation to H&S?
Congenital= vague onset of symptoms.
Acquired = know exact time, date of when symptoms started
Important questions to ask when patients report diplopia?
Vertical/ horizontal?
Monocular/ binocular?
Is amblyopia reported in congenital issues?
If uncontrolled, yes
Versions or ductions used to differential between neuro/ mechanical?
Versions
Do congenital issues have potential for binocular function?
No
What extra tests are done in HES as orthoptic assessments?
Hess, Fields of BSV
Medical - blood tests, BP, CT scan, MRI scan
What is the referral process for palsies?
- All acquired nerve palsies/ motility problems need referral to eye causality.
(Young patients may require a more urgent referral compared to adults - >55 and children- to investigate for aneurysms, tumor, raised ICP). - <55 - often cause is microvascular in origin and therefore referred to eye causality, not life threating. If they have other symptoms i.e. related to stroke- emergency to A&E.
- Known congenital issue in a patient, not symptomatic = no referal.
- Suspected congenital issue, diagnosis not confirmed yet = refer for investigation.
3 types of neurogenic palsies?
- 6th nerve palsy
- 4th nerve palsy
- 3rd nerve palsy
What is seen on 6th nerve palsy?
the 6th nerve supplies lateral rectus. hence, limited abduction when affected.
What is seen in bilateral 6th nerve palsy?
Cause of bilateral 6th nerve palsy?
Both the eyes do not move out when affected side is looking out
Cause: trauma
4th nerve supplies?
Superior Oblique
What is seen in 4th nerve palsy?
Hypertropic + esotropic in primary position
(Not enough pull down)
Role of 3rd nerve?
It supplies medial rectus, superior rectus, inferior oblique muscle. Also innervates muscles of lid and sphincter muscle of the pupil.
What is observed in 3rd nerve palsy?
Droopy lids, when eye are open = hypotropic + exotropic (down & out)
2 causes of congenital nerve palsies?
- Isolated- nerve palsy is the only problem.
- Associated with other conditions- hydrocephalus, cerebral palsy, intoxications from mother, brain tumour (rare).
What causes an isolated nerve palsy?
Lesion to all aspects of the nerve pathway.
Either of the nucleus or nerve.
Most common congenital nerve palsy is?
4th nerve
Difference in how congenital vs acquired palsies look, symptoms?
Congenital: Unacceptable cosmesis, vague onset of when diplopia started or no symptoms. No aware of long standing head posture.
Acquired: Sudden onset of diplopia, aware of uncomfortable AHP.
How is ocular motility different in congenital vs acquired palsy?
Congenital: full muscle sequelae evident.
Acquired: muscle sequelae not fully developed.
How is the vertical fusion in congenital 4 nerve palsy?
Extended vertical fusion, large than expected vertical phoria.
How can you find out if AHP is long standing?
Ask patient to look at old pictures and see if they have always had an AHP.
How is cover test different in neurogenic vs mechanical palsy?
Neurogenic = deviation in primary position reflects extents of palsy. Greater limitation in primary position.
Congenital = often only small deviation in primary position even with a large mechanical limitation of movement.
How is ocular motility different in neurogenic vs mechanical palsy?
Neurogenic: motility is better on ductions than version.
Mechanical: Ductions= versions
How is Hess in neuro vs mechanical palsy different?
Mechanical:Neurogenic: Space between inner and outer fields is equal. Fields displaced close to the inner field in position greatest limitation.
Forced duction test in neurogenic vs mechanical palsy?
Neurogenic: full passive limitation
Mechanical: Limited passive movement
How is IOP in mechanical vs neurogenic palsies?
Neurogenic- same in all positions
Mechanical- increases when looking away from position of limitation.
