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Peds > Anatomy/strabismus > Flashcards

Anatomy/strabismus Flashcards

1
Q

Tenon’s

A

EOMs penetrate Tenon’s to insert to globe
two divisions - anterior - fuses with conj 1 mm from limbus
posterior - separates orbital fat from muscles

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2
Q

intermuscular septum

A

fascial extensions from muscles between rectus muscles

fuses with conj 3 mm posterior to limbus

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3
Q

check ligaments

A

facial extensions between tenon’s and muscle capsule

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4
Q

Sclera thickness at limbus, front of muscles, behind muscles, ON

A 
Memorize thickness:
Limbus - 0.8 mm
Front of muscles 0.6 mm
behind muscles 0.3 mm
at ON 0.1 mm
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5
Q

Lockwood’s ligament

A

fusion of muscle sheaths of inferior rectus and IO
connects lower eyelid retractors
Make sure to disinsert Lockwood’s ligament when doing IR or IO surgery to prevent lower lid retraction

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6
Q

Whitnall’s ligament

A

fascial extension from levator palpebral superioris to SO nasally in area of the trochlea

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7
Q

Muscle lengths
Tendon lengths
Spiral of Tillaux
Muscle origins

A

Muscle length - all rectus approx 40 mm
IO is shortest muscle with shortest tendon (36mm, 1-2 mm respect)
SO longest muscle/longest tendon (60 mm, 30 mm)
Spiral of Tillaux MR - 5.5, SR 6.5, LR 7.0, IR 7.7
Recuts muscles origin - Annulus of Zinn,
IO origin - lacrimal crest
SO origin - medial/sup to annulus of Zinn

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8
Q

Blood supply for EOM

Nerve supply to EOM

A

7 anterior ciliary arteries travel through 4 rectus muscles (All have 2 except LR with 1)

branches of CN enter EOM in posterior 1/3 of muscle on inner aspect
EXCEPT
IO - neurovascular bundle enters mid muscle on outer aspect (some fibers go to ciliary ganglion - can get blown pupil with IO surgery)
Superior division of III - levator and SR
inferior division of III - MR, IR, IO

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9
Q

Felderstruktur fibers vs Fibrillenstruktur

A

FELD: Per Yi: “I felt like having a smooth grape”
for smooth pursuit
innervated in ‘en grappe’ fashion (multiple small nerve fibers)
Unique to EOM

FIBRILLEN: fast saccades
innervated ‘en plaque’ fashion
large myelinated nerve fibers

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10
Q

Sherrington’s law vs Hering’s Law

A

Share one eye - INCR innervation of a given EOM accompanied by DECR innervation of antagonist

HERING’s: equal and simultaneous innervation of muscles in each eye concerned with desired direction of gaze

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11
Q

Conditions that defy Hering’s law

A

DVD
Abberent regeneration of CN III
Duane’s syndrome

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12
Q

Normal fusional amplitudes

A

Remember 3:6:18 for distance and double for near

Vertical: D - 3, N - 6 (Per san antonio, Otherwise normally 2-3 D)
Divergence: D - 6, N -12
Convergence: D - 18, N 36

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13
Q

Two pathways in visual system

A

Magnocellular vs Parvocellular
Parvo - 90% of LGN (central VF and macula), develops by 8 mo
Responsible for stereoPsis, two-Point discrimination
“What info”

Magnocellular (10% of LGN)
for motion - “Where info”
parafoveal and peripheral retina

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14
Q

Horopter

Panam’s area

A

area of maximal stereopsis
region of single binocular vision
locus of all visual point imaged on the retina for a given fixation distance

Panam’s - region around the horopter within which images can be fused.

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15
Q

neurophysiology of amblyopia

anisometropic vs strabismic/deprivational

A

anisometropic: mild vision deprevation
P cell maldevelopment
Gross steropsis intact

Strab/depriv: severe vision deprivation
M cell maldevelopment
poor steropsis

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16
Q

PEDIG results

A

FT patching same as 6 hrs patching for severe amblyopia
2 hrs patching same as 6 hrs for mod amblyopia
patching vs atropine - same for mod amblyopia
atropine weekends vs atropine QD - same

amblyopia recurs within first 3 months of d/c penalization tx
more reverse amblyopia with atropine
Levodopa may be an adjunct to patching for pts up to 18 yr old

17
Q

Monofixation syndrome

type, how to test, prognosis

A

binocular sensory state in pt with small angle strabismus
- central scotoma with good peripheral fusion
have large latent phorias
Test with worth 4-dot test and 4 BO prism test:
Worth 4 dot: at distance, central scotoma in one eye, so will only see 2 or 3 dots
at near, scotoma shrinks and pt should see all 4 dots if ARN (will see 5 dots if NRC)

4 BO prism test: normally - eye will turn out and then refixate in
in monofixation when prism in front of normal eye - eyes will turn out, but not refixate
in front of scotoma eye - no initial turn out.

= good prognosis for long term alignment

18
Q

ARC:

tests

A

corresponding areas of retina have dissimilar relationship to respective foveas

Bagolini test and after image test
also amblyoscope and red glass test

19
Q

types of amblyopia

complications from patching

A

stabismic (cong ET 40%, accom ET 25%, Int XT <2%)
Refractive
Deprivation

Contact dermatitis
Strabismus
reverse amblyopia

20
Q

infantile esotropia

A 
ET > 35 PD
refraction normal
present before 6 mo, crossfixation early
\+ FHx
Associated with DVD, IO overaction, latent nystagmus,
21
Q

Accomodative ET

A

onset after 1.5 yrs

ET 3 D (can stop crossing after +7)

22
Q

How to measure AC/A method
Heterophoria method
Lens gradient method
Near/Distance deviation difference

A

Heterophoria = IPD + deviation at Near - deviation at distance/accomodation in D at near

Lens Gradient: Dev at N (w/lens) - Deviation at N (without lens)/Lens power

Deviation at near - deviation at distance (high AC/A if greater than 10 -15 PD)

23
Q

intermittent exotropia

A

most common XT
may be progressive
amblyopia uncommon

24
Q

congenital XT

A

rare
large angle deviation
most resolve by 6 months
Assoc: DVD, oblique muscler overaction, Cruzons, albinism, fetal alcohol, CP

25
Q

Convergence insufficiency

A

exophoria greater at near than distance

decr NPC and amplitudes of convergence

26
Q

Divergence insufficiency

A

ET greater at distance
Fuse at near
** rule out divergence paralysis (pontine tumor, head trauma) = no fusional vergence

27
Q

ciliary spasm

A

intermittent episodes of sustained convergence

Sx: headache, blurry VA at distance, abnormally close near point,

Peds (5 decks)

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