Strabismus Flashcards
The cover test can show ___ while the alternate cover test can reveal ___. In a patient with manifest strabismus, the cover test cover should be placed on the fixating/nonfixating eye?
cover: tropia
alt cover: phoria
- cover should be placed on fixating eye, to make nonfixating eye come back to primary
when quantifying strabismus, a glass prism should be held ____ while a plastic prism _____
glass: perpendicular to the visual axis of the deviating eye (out at angle angle to face)
plastic: perpendicular to the visual axis of the fixating eye (parallel to face). this is the more common type of prism uses in the office setting
which test measures strabismus using the corneal light reflex only, and what ratio of deviation to prism diopters is assumed in this test?
Hirschberg; ~20 D/mm. for a 3 mm pupil, a light reflex at the pupil margin means 30 D. Mid iris (3 mm from center) is 60 D, and limbus (~6mm from center) is 90 D
which strabismus measurement tests are best for uncooperative patients
Hirschberg and Krimsy; cover/alt cover w/ prism requires fixation and is difficult in uncooperative patients
how is the Krimsky test done?
place prisms over the deviating eye until the corneal light reflexes are centered
orthotrpoic patients have a ___ angle kappa. esotropics have ____ and exotropics ____.
normal and exo: positive angle kappa (fovea temporal to pupillary axis, so light reflex is nasal)
eso: negative angle kappa (fovea nasal to pupillary axis, and light reflex is temporal)
can Maddox rod testing differentiate phorias from tropias?
no, because fusion is precluded
In Maddox rod testing, if the white light is seen above the red line (assuming red cover over right eye), what deviation is present? What is the white light is seen to the right of a vertical red line?
left hypodeviation, or right hyperdeviation
crossed –> exodeviation
uncrossed –> exodeviation
What is the practical use of the LAncaster red-green tests, and what criteria must be met for this test to be useful?
good for complicated incomitant strabismus, but must have normal retinal correspondence
fusional convergence eliminates _____ retinal disparity, and fusional divergence eliminates ______ retinal disparity.
convergence eliminates bitemporal retinal disparity (nasal VF of each eye would be different without this fusion; think of looking close up and each eye has a different nasal field of your nose)
divergence eliminates binasal retinal disparity (
cutoff for high AC/A ratio when measured by heterophoria method?
this takes the difference in deviation at far v near. A difference of 10 or more prism diopters is considered a high AC/A
average fusional vergence amplitudes at far and near for convergence, divergence, and vertical?
convergence: 14, 38
divergence: 6, 16
vertical: 2.5, 2.6
What are the Bielcschowsky 3-step findings for paralysis of each cyclovertical muscle?
RRR: LIO RRL: RIR RLR: RSO RLL: LSR LLL: RIO LLR: LIR LRL: LSO LRR: RSR
head positioning for a SO palsy?
chin down and head turn and head tilt AWAY from side of lesion
head positioning for Brown’s?
chin up, contralateral head turn
patient with RSO palsy and right head tilt?
paradoxical head tilt, likely to reduce conflict between two images when fusion is not possible
torticollis that improves with supine positioning?
unlikely musculoskeletal, more likely ocular
chin positioning for V pattern esotropia? A pattern exotropia?
chin down for both (more orthotropic in upgaze)
3 responses to ocular misaligment
diplopia, ARC, or suppression
What is suggested by crossed images in the red-glass test? By uncrossed but nonoverlapping images? How can you determine ARC v NRC? What if only a red dot is seen?
- crossed: exotropia
- uncrossed: esotropia
- If image disparity is equal to that of previously measured deviation (such as from prism alt cover), then NRC is present
- If image disparity is less than previously measured deviation or if overlapping of images is present, then ARC is present
- If only a red dot is seen, then suppression is present
In the 4 prism diopter base out prism test, what will happen when the prism is placed over the fixing eye in monofixation syndrome? the nonfixing eye?
- fixing eye: both eyes will move away from fixating eye
- nonfixating: no effect (disrupting the suppressed eye does nothing to the eye which is fixating)
*Of note, it is possible that the patient alternates fixation and therefore alternates suppression, and shows no movement regardless of which eye is being covered
What is the best purpose of the Worth 4-dot test?
to test for a suppression sctotoma
What are the possible findings of the Worth 4-dot test and what does each indicate?
(remember, red glass over right eye and green glass over left eye. orientation of dots is red on top, green to sides, and white on bottom)
- 2 vertical red: suppression of left eye
- 3 green: suppression of right eye
- 4 dots with red-green competition of the bottom dot: orthophoria with NRC, or manifest deviation with harmonious ARC
- 5 dots with red dots to the right: uncrossed deviation = esotropia
- 5 dots with red dots to the left: crossed deviation = exotropia
Findings in monofixation syndrome with Worth 4-dot test
suppression at distance (2 or 3 dots) but no suppression at near (4 dots), because at near, the dots will fall on peripheral retina outside of suppression scotoma
RF for esotropia
family history, hyperopia, maternal smoking during pregnancy, anisometropia, prematurity, low birth weight, neurodevelopmental impairment
% amblyopia in children with esotropia
50%
how to differentiate pseudoesotropia from esotropia
normal corneal light reflex in the former
age cutoff for infantile esotropia
present by 6 months of age
common findings in infantile esotropia
cross fixation (leading to apparent abduction deficit), DVD, overelevation in adduction, latent nystagmus
55 prism diopter esotropia in 4 month old with cross fixation, mild abduction deficits and abducting nystagmus?
Ciancia syndrome
reasonable goals for surgery for infantile esotropia?
8-10 prism diopters or less with the development of monofixation syndrome
timing of surgery for infantile esotropia
as early as 4 months, no later than 24 months
most common surgery for congenital esotropia
bilateral medial rectus recession (BMRc)
effect of Botox injection on EOM, and how long before it wears off?
paralyzes and lengthens muscle; lasts 5-8 weeks (as opposed to orbicularis Botox injections which last 3-4 months)
typical age of presentation for accommodative ET?
6 months - 7 years, averaging around 2.5 years
intermittent ET in a 2 year old that becomes constant by 3 years old?
likely accommodative ET
triad of factors leading to refractive accommodative esotropia
uncorrected hyperopia, compensatory accommodative convergence, and inadequate fusional divergence
normal range of ET at distance and near for refractive accommodative ET? average refractive error?
20-30 prism diopters, equal at distance and near. average of 4.00 D of hyperopia
patient with CRx 2.25 D hyperopia and esotropia only present at near despite refractive correction: diagnosis, treatment
high AC/A ratio esotropia. bifocals are mainstay: should be executive flat top-style with bifocal bisecting the pupil and the lowest plus power needed
treatment of refractive accommodative ET
Full CRx!!! also treat for amblyopia if present. remeasure CRx if eso still present, and consider surgery if stil > 8-10 prism diopters
patient about to undergo surgery for 30 D esotropia that manifested at 2.5 years of age. patient has iris cysts and mild cataracts that developed recently. what very important preoperative consideration must be made?
scenario suggests that patient is using ecothiophate, a long-acting cholinesterase inhibitor, for accommodative ET. succinycholine CANNOT be given to this patient for anesthesia, as the ecothiophate will prevent its breakdown and lead to prolonged muscle paralysis including diaphragmatic weakness causing respiratory compromise
normal trend in refractive error through early life?
begin hyperopic, increase hyperopia until 5-7 years, then become progressively more myopic
surgical approach to partially accommodative esotropia?
correct only for esotropia that persists with glasses on. eyes will not be straight post-op when glasses are off
6 year old with no previous ocular history is head in head with stick and develops hyphema. affected eye is patched for a week, and upon follow up esotropia is detected: diagnosis, workup, management
acute esotropia. often develops after prolonged disruption of fusion (hyphema, patching, ptosis, preseptal cellulitis). should consider neuroimaging in patients with acute ET with other symptoms. treatment is surgical.
average cycle length for cyclic esotropia? is diplopia usually present during cycles of ET? treatment?
48 hours. diplopia more rare in younger children who can suppress, but may be found in older patients. Tx is surgery for maximum deviation detected on strabismus days.
esodeviation greater at distance that near?
divergence insufficiency
diagnosis and management of intermittent ET in teenager that manifests during versions as a substitute for horizontal gaze?
spasm of near reflex; reassurance as is often related to stress and anxiety. treatment includes cycloplegica, hyperopic correction, and Botox of MR for residual cases
head turn in patient with 6th nerve palsy
toward side of lesion
most common strabismus in Europe and Americas? In Asia?
esodeviations more common in Western world
exodeviatons more common Asia
RF for exodeviations
family history, premature birth, maternal smoking during pregnancy, Asian ancestry, uncorrected refractive error
differential for intermittent XT that is worse at distance? how can you differentiate between the possible causes?
pseudodivergence excess due to tenacious proximal fusion (more common), or true divergence excess due to high AC/A ratio (rare). If you perform monocular occlusion for 30-60 minutes prior to measuring XT at distance and near, this will break proximal fusion and measurements will be equal at distance and near for pseudodivergence excess. If XT still greater distance, then true divergence excess is present (high AC/A ratio)
XT greater at near than distance?
convergence insufficiency. Tx involves base out prisms to challenge the eyes to converge (orthoptic exercises). If these fail, can use base in prisms to improve XT
most common surgical treatment for pseudodivergence excess?
bilateral LR recession, but this is not hard and fast
approach to refractive correction in intermittent XT?
generally only correct hyperopia > 4.0 D or anisohyperopia > 1.5 D, because correcting hyperopia will decrease accommodation and can worsen XT
which is a more desirable outcome for XT surgery: mild XT or mild ET?
mild ET is more acceptable and will often resolve; residual XT often gets worse
V pattern is more common in ____, and significant V pattern is greater than _____ prism diopters.
A pattern is more common in ____, and significant A pattern is greater than _____ prism diopters.
V: esotropia. >/= 15 prism diopters (larger than A pattern becuase there is some physiologic convergence in down gaze)
A: exotropia. >/= 10 prism diopters
Rule of thumb for vertical transposition of horizontal muscles to correct A and V pattern eso- and exotropias?
MALE: medial to the apex, lateral to the empty space
*Applies regardless of whether horizontal muscle is being resected or recessed
Example: V pattern esotropia, will perform medial rectus recession with inferior displacement of the MR (inferior is to the “apex” of the “V”)
Surgery for A/V pattern strabismus with ODAd/OEAd? Without?
With: weakening of the SO/IO
Without: vertical transposition of horizontal muscles according to MALE rule
treatment of V pattern esotropia with DVD?
anterior transposition of IO
treatment of A pattern ET in Trisomy 21 patients?
vertical transposition of horizontal rectus muscles
Double Maddox rod test findings in right SO palsy
- right hypertropia with right extorsion
- red line (right eye) will be under the white line, and the nasal aspect will be lower
(line appears opposite of what deviation is)
how long to wait after cranial nerve palsy to do strabismus surgery?
6 months
surgical approach to CN IV palsy
up to 15 D of hypertropia: ipsilateral IO weakening.
> 15 D: ipsilateral IO weakening + contralateral IR weakening
surgical approach to bilateral CN IV palsy with minimal hyperdeviation but 25 D excyclotorsion and symptomatic diplopia?
Harada-Ito (bilateral transposition of anterior torsional fibers of SO to increase intorsion)
Differentiate IO palsy from Brown’s
- Brown’s: positive forced ductions, worse on retropulsion, may have V pattern
- IO palsy: intorsion, positive Bielschowski head tilt, SO overaction, may have A pattern strabismus
what is the Knapp procedure
vertical transposition of MR and LR i patients with monocular elevation deficiency
surgery of choice for esotropia in non-active TED patient with residual tight right MR
NEVER DO RESECTIONS!! This can lead to Globe retraction. Operating directly on the affected muscle is best. Thus, right MR recession is best. If larger deviation, can also recess left MR
surgery for isolated DVD?
SR recession. IR resection for residual
pathophysiology of Duane’s?
manifests in week 4-6 of gestation. agenesis of 6th nerve nucleus with aberrant regeneration of LR from CN III leading to co-contraction of MR and LR on attempted gaze in either direction. Usually MR is stronger leading to a more predominant ABDuction deficit (Type 1)
types of Duane syndrome? most common?
1: limitation of ABDuction (most common: 50-80%)
2. limitation of ADDuction
3. limitation of both abduction and adduction
esotropic patient with very limited abduction in one eye, narrowing of PF on attempted abduction, and on adduction of that eye, the eye downshoots
Duane’s (can upshoot or downshoot on adduction, probably from LR slippage)
systemic associations with Duane’s?
Goldenhar, maternal thalidomide
differentiate CN 6 palsy form Duane’s
CN 6 palsy will have much greater eso at primary position. Duane’s will have globe retraction on attempted abduction, and may have upshoot or downshoot of involved eye on adduction.
surgery of choice for type 1 Duane’s? Type 2?
**Except for rare scenarios, resections are NOT DONE as they may worsen globe retraction!
Type 1: ipsilateral MR recession. can recess bilaterally for larger deviations
Type 2: ipsilateral LR recession. can recess bilaterally for larger deviations
Type 3: recess LR and MR. can recess bilaterally for larger deviations
patient with inability to elevate either eye and with bilateral upperlid retraction, both since birth. sister suffers from same symptoms: diagnosis and management
congenital fibrosis of extraocular muscles, affecting superior division of CN III. recession of SR and LPS
mask-like facies with bilateral abduction deficits? management?
Mobius syndrome (bilateral CN 6 and CN 7 palsies). MR recession is probably first line
management of acute onset Brown’s?
CT orbits and sinuses to evaluate for sinusitis, which can cause acquired Brown’s
% bilaterality of Brown’s?
10%
effect of retropulsion of globe in Brown’s patient?
will worsen restriction by further tightening SO tendon
differentiate So overaction from the downshoot in adduction in Brown’s?
Brown’s downshoot is much more abrupt
head position in Brown’s?
may have chin down
systemic disease that can cause Brown’s?
rheumatoid arthritis
method to test possibility of post-op diplopia in adult patient with CN III palsy ?
prism adaptation: correct deviation with prisms. if this gives diplopia, patient may have ARC. many patients grow out of this and can tell which image id the real one, but others will not be pleased
time to wait for surgery with CN III palsy?
adults: at least 6 months. congenital: don’t wait as can lead to amblyopia
surgical options for CN palsy?
- incomplete: large MR resection
- complete: large LR recession with fixation of globe to nasal orbital periosteum. can also disinsert LR and reattach to lateral periosteum to maximize inactivation. may also perform SO tenotomy or transposition to decrease hypotropia
- ptosis is often corrected at a subsequent procedure
order of decreasing frequency of involvement of EOMs in TED
“I M SLO”
IR (most commonly involved), then MR, SR, LR, obliques
indications for surgery for TED
diplopia, abnormal head positioning
side effect of large IR recession?
eyelid retraction; can resect lower lid retractors to prevent this
child with bilateral ptosis and slowly progressing bilateral restriction of eye movements. fundus exam shows pigmentary retinopathy: diagnosis and workup?
Kearns-Sayre syndrome (special type of CPEO); order skeletal muscle biopsy looking for ragged red fibers, and ECG to evaluate for heart block
what is a Cogan lid-twitch and what does it usually indicate?
overshoot of eyelid when looking straight after prolonged down gaze; highly suggestive of myasthenia gravis
how long should you hold an ice pack over a patient’s eyes when testing for myasthenia?
2-5 minutes
what medications can be used to diagnose myasthenia?
edrophonium (i.e. Tensilon) or neostigmine, which are acetylcholinesterase inhibitors
ocular misalignment in high myopia?
esotropia and hypotropia, from slippage of SR and LR
patient with apparent bilateral abduction deficits but upon thrusting his head to the side and returning to primary gaze is able to maintain horizontal gaze?
ocular motor apraxia
convergence retraction nystagmus and paralysis of upgaze in child?
dorsal midbrain lesion, likely pinealoma or congenital aqueductal stenosis in child
positioning of prisms for a patient with nystagmus?
apex pointed toward the null point
surgical correction for nystagmus?
eyes are surgically rotated towards the direction of the head turn and away from the null point
table to guide amount of recession/resection of MR/LR depending on degree of eso/exo
ESO:
15 D: 3mm MR recess OU or 4mm LR resect OU
20 D: 3.5mm MR recess OU or 5mm LR recess OU
…and so on
EXO
15 D: 3mm MR resect OU or 4mm LR recess OU
20 D: 4mm MR resect OU or 5mm LR resect OU
…and so on
what is a hang-back recession?
the muscle tendon is suspended by a suture attached to the original insertion, and it is unknown exactly where the tendon reattaches to the sclera. this can be very useful when navigating around scleral buckles or glaucoma drainage implants
rule of thumb for amount of prism diopter change per mm of vertical muscle recession
3 prism diopters per mm recession
how long to wait for reoperation for post strab diplopia?
at least 4-6 weeks
slippage of which EOM is most dire?
MR, because is hardest to recover (has no oblique running tangentially to it as a landmark)
where do lost muscles reattach o the globe?
they do not reattach; they retract through Tenon’s capsule
reason for slipped muscles?
inadequate suturing techniques
where does dehiscence of a muscle during surgery (pulled-in-two syndrome) generally occur
at tendon-muscle junction; most common is IR
management of scleral perforation in strab surgery
see if vitreous escapes, and if so apply topical abx. many surgeons perform laser or cryo to the site. post-op ophthalmoscopy with referral to retina as needed. most scleral perforations only result in small chorioretinal scars, but RD or endophthalmitis can occur
management of posterior Tenon’s tear with fat prolapse?
excision of prolapsed fat with repair of Tenon’s defect with absorbable sutures
earliest sign of anterior segment ischemia?
cell and flare
earliest sign of malignant hyperthermia?
elevation of end-tital CO2
