Ocular Motility - OMT 270 Flashcards
(30 cards)
Zippy Lomax
PCC Eye Tech Program
Ocular Motility Flashcards – Part 1 & 2
Extraocular Muscles & CNs
MR - CN III
LR – CN VI
SR – CN III
IR – CN III
SO – CN IV
IO – CN III
🧠 mnemonic: SO4, LR6 — all the rest are 3
there are 6 extraocular muscles:
Medial Rectus (MR): CN III (Oculomotor)
Lateral Rectus (LR): CN VI (Abducens)
Superior Rectus (SR): CN III
Inferior Rectus (IR): CN III
Superior Oblique (SO): CN IV (Trochlear)
Inferior Oblique (IO): CN III
👁️ each cranial nerve controls eye movement by innervating specific muscles — damage to any can cause diplopia or gaze limitations
Actions of Each Muscle
Primary & Secondary
MR: Adduction
LR: Abduction
SR: Elevation, Intorsion, Adduction
IR: Depression, Extorsion, Adduction
SO: Intorsion, Depression, Abduction
IO: Extorsion, Elevation, Abduction
→ secondary actions italicized
✨ tip: think of primary action as what the muscle mainly does when the eye is in primary gaze – secondary actions kick in as eye position changes
Muscle Origins & Insertions
(for 4 recti + formation)
all recti originate at the Annulus of Zinn, insert on anterior sclera, spiralling around globe (Spiral of Tillaux)
→ MR = closest, SR = furthest from limbus
🌀 imagine muscles wrapping around the eye like a spiral staircase
origin:
→ common tendinous ring
→ (Annulus of Zinn; a fibrous ring at the apex of the orbit)
insertions:
→ anterior to the eye’s equator, on the sclera of the globe
distance from limbus varies:
→ MR: closest
→ IR
→ LR
→ SR: farthest
→ these insertions create the Spiral of Tillaux
Mnemonics
‘SO4, LR6, All the Rest 3’
‘BID on IOUs’
→ EOM innervation
→ IO actions
SO = CN IV
LR = CN VI
all other EOMs = CN III
→ helps easily identify innervation of extraocular muscles
actions of Inferior Oblique (IO):
B = extorsion (rotates top of eye outward)
I = elevation (raises the eye)
D = abduction (moves eye outward)
→ IO is the only muscle that both elevates and abducts – it’s the quirky outlier!
💡 alternate IO mnemonic:
‘Inferior Obliques Elevate the Outcast Eye’
Elevate = elevation
Outcast = abduction (moves out)
Eye Twist = extorsion
Nine Diagnostic Positions of Gaze
primary:
→ straight ahead, looking directly at the target
right:
→ looking to the right
left:
→ looking to the left
upward:
→ looking directly upwards
up & right:
→ looking diagonally upwards & to the right
up & left:
→ looking diagonally upwards and to the left
downward:
→ looking directly downwards
down & right:
→ looking diagonally downwards and to the right
down & left:
→ looking diagonally downwards and to the left
→ use an ‘H’ pattern to isolate EOMs
art prompt: create a symmetrical face diagram with dotted gaze directions and muscle initials
Two Main Laws Governing Eye Movements
Hering’s Law of Equal Innervation
(yoked muscles)
Sherrington’s Law of Reciprocal Innervation
(agonist/antagonist pairs)
Hering’s:
→ yoked muscles (e.g., RLR + LMR) receive equal neural signals
→ explains coordination in binocular eye movement.
Sherrington’s:
→ reciprocal neural signals
→ when one contracts, its antagonist relaxes
→ example: LMR contracts → LLR relaxes.
Duction, Version, Vergence
duction = movement of one eye only (e.g., abduction, elevation)
version = both eyes move in same direction (e.g., right gaze)
vergence = eyes move in opposite directions (e.g., convergence = inward, divergence = outward)
visual prompt: design a trio of simple side-profile sketches showing one eye moving, two eyes moving together, and two eyes moving inward/outward
Ideal Motility Exam Order
- observation
- Hirschberg test
- cover/uncover test
- extraocular motility (EOMs: versions, ductions)
- NPC/NPA
- diplopia charting
- fusion testing
- Worth 4 Dot test
- Maddox Rod test
- Bielschowsky Head Tilt Test (BHTT)
ensures organized assessment→ gross alignment to fine binocular function
art prompt: create an elegant vertical flowchart with icons representing each exam step
Monocular vs Binocular Diplopia
monocular = persists with one eye covered (ocular issue)
binocular = resolves with one eye covered (alignment issue)
monocular diplopia:
→ still evident when one eye is covered
→ indicates a problem within the eye (e.g., cornea, lens)
binocular diplopia:
→ disappears when either eye is covered
→ caused by ocular misalignment (neuromuscular or neurologic)
🧠 mnemonic: ‘Binocular = Brain’ → more likely neurological
visual prompt: side-by-side face icons showing double vision with both eyes vs one eye covered
Orthophoria, Phoria, Tropia
orthophoria = perfect alignment
phoria = latent misalignment
tropia = manifest misalignment
orthophoria:
→ perfect alignment of the eyes without effort
→ no deviation, latent or manifest
phoria:
→ latent deviation controlled by fusion
→ only revealed when binocular vision is interrupted
tropia:
→ manifest deviation present even when both eyes are open
→ fusion can’t fully correct it
visual prompt: draw three face diagrams: aligned (orthophoria), eye drifting when covered (phoria), and eye turned at rest (tropia)
Define NPC & NPA
NPC = closest point of convergence
NPA = closest point of accommodation (focusing)
NPC (Near Point of Convergence):
→ closest point the eyes can maintain binocular fusion while converging
→ assesses teamwork of medial recti & convergence ability
NPA (Near Point of Accommodation):
→ closest point of clear vision (single eye or binocular)
→ related to lens flexibility & focusing power
test tip: use a penlight or small target (fixation stick), move toward the nose – note blur or divergence point
art prompt: draw converging eyes with arrows and a (blurry) target approaching the nose
Four Types of Strabismus Deviations
eso = inward
exo = outward
hyper = upward
hypo = downward
→ deviations can be manifest (tropias) or latent (phorias) – can affect one or both eyes
visual prompt: simple eye diagrams with arrows pointing in, out, up, down — label accordingly
Cover Test Types & What They Reveal
cover:
cover one eye → detects tropia
(look for shift in uncovered eye)
cover/uncover:
briefly cover one eye → detects phoria
(watch for movement as fusion re-engages)
alternate:
switch cover between eyes repeatedly → breaks fusion & reveals total deviation
prism cover:
performed with prisms to quantify deviation in prism diopters
art prompt: series of 3-step illustrations showing each method
Hirschberg vs Krimsky Tests
Hirschberg:
→ shine light into both eyes and observe corneal light reflex
→ reflex location estimates strabismus (e.g., nasal = exo)
Krimsky:
→ add prisms to center the reflex → quantifies deviation
→ visual tip: reflex 1 mm off = ~15 prism diopters of deviation
art prompt: two sets of eyes — one showing asymmetric light reflex (Hirschberg), another with prism correcting the reflex (Krimsky)
Worth 4 Dot Test
results:
sees 4 dots = fusion
sees 2 red or 3 green = suppression
sees 5 dots = diplopia
→ used to evaluate fusion and detect suppression or diplopia
setup:
→ patient wears red/green glasses
→ patient looks at screen or flashlight with 4 lights
→ 1 red (top), 2 green* (sides),* 1 white (bottom)
art prompt: colored dot layout + goggles icon for easy recall
Maddox Rod Test
results:
→ line & dot not aligned = deviation
→ vertical separation = horizontal phoria (eso/exo)
→ horizontal separation = vertical phoria (hyper/hypo)
→ used to detect phorias/tropias by disrupting fusion
setup:
→ Maddox rod placed over one eye (usually red)
→ patient views point light
visual tip: Maddox = line & dot
art prompt: simple red line vs white dot illustration
Bielschowsky Head Tilt Test
three-step test:
1. determine hypertropic eye
2. look for change with gaze direction
3. assess vertical change with head tilt (positive if deviation increases when tilting toward affected muscle)
→ helps identify a vertical muscle palsy (usually SO or SR)
visual prompt: sketch faces tilting with exaggerated vertical misalignment
Conjugate vs Disconjugate Movements
conjugate = same (versions)
disconjugate = opposite (vergence)
conjugate: eyes move together in the same direction (versions)
disconjugate: eyes move in opposite directions (vergence)
examples:
→ looking left = conjugate
→ converging = disconjugate
🧠 mnemonic: ‘disco = divergence!’
art prompt: paired eyes with arrows pointing same vs opposite directions
Yoke Muscles and Versions
yoke muscles: paired muscles in each eye that move together in versions (e.g., RLR + LMR)
version movements:
→ dextroversion = right gaze
→ levoversion = left gaze
→ supraversion = up
→ infraversion = down
art prompt: 6-point compass rose labeled with version terms + yoke pair example
Fusion and Suppression
fusion = combine images into one
suppression = brain ignores one image
fusion:
→ the brain’s ability to merge two slightly different retinal images into one
→ requires alignment and equal image quality
suppression:
→ the brain ignores input from one eye to avoid diplopia
→ often develops in strabismus or amblyopia
art prompt: twin eye beams merging into one glowing image; one beam dimmed for suppression
Amblyopia: Definition & Causes
amblyopia = ‘lazy eye’
→ decreased vision in one eye due to poor neural development
→ not correctable by glasses alone
causes:
→ strabismus (misalignment)
→ refractive error (anisometropia)
→ deprivation (e.g., cataract)
Comitant vs Incomitant Deviations
comitant = same deviation all gazes
incomitant = deviation varies by gaze
→ visual tip: ‘Comitant = Constant’
comitant:
→ angle of deviation is the same in all directions of gaze
→ suggests longstanding or congenital strabismus.
incomitant:
→ angle changes with gaze direction.
→ suggests neurological or mechanical cause
art prompt: grid of gaze positions showing equal vs shifting deviation angles
Red Glass Test
setup:
→ red filter over one eye
→ patient views white light
findings:
→ sees two lights; red and white, separated → diplopia
→ relative positions indicate type of deviation;
→ eso/exo, hyper/hypo, horizontal/vertical/diagonal
→ used to detect diplopia and determine deviation type
