Strabismus Flashcards
What is the function of the medial rectus?
it adducts the eye
What is the function of the lateral rectus?
it abducts the eye
What are the functions of the superior rectus muscle?
it primarily elevates the eye
it also adducts & intorts the eye
What are the functions of the inferior rectus muscle?
it depresses, adducts, and excyclotorts the eye
What is the function of the superior oblique muscle?
depresses & intorts the eye
What is the function of the inferior oblique muscle?
elevates & extorts the eye
Which extra ocular muscles are innervated by the 3rd CN?
medial rectus inferior rectus superior rectus inferior oblique levator palpebra
Which extra ocular muscles are innervated by the 4th CN?
innervates the superior oblique
Think SO4
Which extra ocular muscles are innervated by the 6th CN?
lateral rectus
What are ductions?
movements of one eye
What are versions?
movements of both eyes in the same direction (conjugate)
What are vergences?
movements of both eyes in a disconjugate way (not same direction)
What is strabismus?
misalignment of visual axes
What is phoria?
latent deviation of eyes
**appears only when fusion disrupted
What is tropia?
manifest deviation
**beyond the range of fusional control
What is esotropia?
nasalward deviation of an eye (cross eye)
What is exotropia?
temporal deviation “wall eye”
What is hypertropia?
vertical deviation, relative to higher eye
What is concomitant strabismus?
- *this is where the angle of deviation remains constant regardless of the direction of gaze
- *range of motion of eyes is full-without limitations
What is incomitant strabismus?
- *this is where the angle of deviation varies with the direction of the gaze
- *ocular movements are limited
- *pt may have head in an abnormal posture to maintain binocularity…
Which type of strabismus is more commonly seen in childhood onset strabismus?
concomitant strabismus more common
Is incomitant strabismus congenital?
it can be…or it can be acquired.
In which type of strabismus do you esp see abnormalities of binocularity, motion processing, poor fusional vergences?
comitant strabismus
Which type of developmental diseases can lead to incomitant strabismus?
Duane’s
Brown’s
mobius
Which type of neurologic diseases can lead to incomitant strabismus?
cranial nerve palsy
myasthenia
Which type of restrictive diseases can lead to incomitant strabismus?
orbital fractures-trauma
grave’s disease-thyroid disease
congenital fibrosis syndrome
What are some important tests to do when diagnosing strabismus?
cover test, alternate cover test light reflex testing angle of deviation measured with prisms motility evaluation for ductions & versions sensory testing to assess binocularity
What is pseudoesotropia? Which category does this fall into? Which age group is this common in? What are some of its other characteristics?
this is where the eyes appear to be crossed, but really they are straight & properly aligned
**characteristics: wide flat nasal bridge, epicanthal folds
**common in infants
Category: comitant strabismus
How does pseudoesotropia do with light reflex & cover tests?
all is normal with these tests, b/c there really isn’t a problem, just large epicanthal folds.
What is congenital esotropia?
this is a congenital condition in which the eyes are turned inward
there is a large angle deviation, cross fixation, and limitation of abduction
Congenital esotropia is often confused with which condition? What is the treatment? Which category does it fall into?
confused with congenital sixth nerve palsy
requires surgical treatment
falls into the category of comitant strabismus
What is accommodative esotropia? Which category does it fall into? What is the usual age of onset?
this is where the eyes are deviated inwardly somewhat, but really only b/c the kid is trying to focus–over-convergence related to accommodation in hyperopia
- *usual onset: 2-3 years
- *comitant strabismus
What is the treatment for accommodative esotropia?
glasses
bifocals are sometimes necessary
What is exotropia? Which category does this belong to? Which age group does this affect?
eyes deviate outward when fatigued or not paying attention
normal binocular vision when eyes are straight
seen intermittently in childhood
belong to comitant strabismus category
What is Duane’s Retraction Syndrome? Which category does this fall into?
absence of 6th nerve nucleus–deficient abduction
miswiring of 3rd nerve–cocontraction of medial & lateral rectus.
**gives globe retraction on adduction
Category: Incomitant Strabismus, developmental
What is mobius syndrome? Which category does it fall into?
congenital bilateral 6th & 7th nerve palsies.
Category: Incomitant Strabismus, developmental
What is Brown’s syndrome? Is it congenital? Which category does it belong to?
abnormality of a trochlear pulley–superior oblique problems
deficit of elevation of eye in adduction
**can be congenital or acquired
**Incomitant Strabismus, Developmental
What is congenital fibrosis syndrome? How is it inherited? What is its category?
w/ this syndrome you have inelastic muscles & ptosis
get positive forced ductions
autosomal dominant disorder
Incomitant Strabismus, Restrictive
How does Graves’ disease lead to eye problems? Which category does it fall into?
you get lymphocyte infiltration & secondary fibrosis of the extra ocular muscles
Category: Incomitant Strabismus, Restrictive
What’s the deal with orbital fractures? Which category does this fit into?
this causes scarring or entrapment of orbital tissues & extra ocular muscles…
Category: Incomitant Strabismus, Restrictive
What are some things that can cause cranial nerve palsies & neurological incomitant strabismus?
microvascular problems
a tumor
trauma
aneurysm
What is the specific effects seen in 3rd nerve palsy?
the eye moves down & out
you get droopy eyelid (ptosis)
sometimes have pupillary involvement
What are the specific effects seen in 4th nerve palsy?
oblique diplopia & torsion
this is seen bilaterally, usu following trauma
What are the specific effects seen in 6th nerve palsy?
difficulty with abduction of eyes
face turns towards the affected side
What’s the deal with myasthenia gravis? Which category does this fall into?
this is a problem involving acetylcholine receptor antibodies
you get variable strabismus & ptosis
can use the tensilon test
Category: Neurological Incomitant Strabismus
When you do recession in strabismus surgery…what happens to the eye you operate on?
it weakens the effect of this operated muscle
When you do resection in strabismus surgery…what happens to the eye you operate on?
this enhances the effect of the operated muscle
When transposition happens in strabismus surgery…what is the result?
this shifts the force vector of the muscle
What happens in normal single binocular vision? What is steropsis?
there is a fusion of images from both eyes
if you get sufficient fusion you get stereopsis & you can have depth perception.
