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Extra Ocular Movements
(aka) …and you thought hyperopia was bad…
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WHAT ARE WE GOING TO DO T’DAY?
Some (very, very little) Basics Extra Ocular Muscles Innervation Control of movements Movements Terminology Actions Testing
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BASICS
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The Extra Ocular Muscles
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The Extra Ocular Muscles -Origin
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The Extra Ocular Muscles -Origin
TROCHLEA SR SO Annulus LR MR IR IO
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The Extra Ocular Muscles -Origin
TROCHLEA SR SO MR LR IR IO
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The Extra Ocular Muscles -Origin
SR SO LR IO IR
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The Extra Ocular Muscles -Origin
SR TROCHLEA SO MR IO IR
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The Extra Ocular Muscles
SR SO MR LR IR IO
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The Extra Ocular Muscles
IO SO MR LR SR
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The Extra Ocular Muscles
SR SO LR MR IO IR
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The Extra Ocular Muscles
MR SR LR
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The Extra Ocular Muscles
SO IO 51° 23° SR IR OPTICAL AXIS
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THE EXTRA OCULAR MUSCLES
Superior & Inferior Recti make an angle of 23° with the eye ball Superior & Inferior Obliques make an angle of 51° with the eye ball Angular attachment allows for actions in multiple directions
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INNVERVATION LR6 SO4 O3
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SOME RULES
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RULES #1 BOTH EYES MUST MOVE TOGETHER
MUSCLES IN BOTH EYES ARE THUS PAIRED PARIED MUSCLES (YOKE MUSCLES) HELP MOVE THE EYE IN A GIVEN DIRECTION. THEY BOTH THUS GET SIMILAR STIMULATORY SIGNALS FROM THE BRAIN (HERRINGS LAW)
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RULES #2 MUSCLES IN ONE EYE HAVE AN AGONIST- ANTAGONIST RELATIONSHIP
THE HORIZONTAL RECTII FORM ONE SET THE VERTICAL RECTII/ OBLIQUES FOR THE OTHER SET WHEN ONE MUSCLE IN THE SET CONTRACT THE OTHER MUST RELAX (SHERRINGTON’S LAW)
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RULES #3 MUSCLE ACTIONS & TESTING ARE DIFFERENT!
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CONTROL OF MOVEMENTS
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WHY? Eyes; you have to see
Eyes must ‘fix’ on an object for you to see clearly Two Step process Find what you want to see (Voluntary fixation) Keep your eyes ‘glued’ to it (Involuntary fixation)
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STEP 1: Find what you want to see
STEP 2: Keep your eyes fixed on it
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SUPRA NUCLEAR: CONTROL MEHANISM
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CONTROL MECHANISMS INVOLUNTARY VOLUNTARY
Tremors (Help keep image refreshed) Drifts (Help keep image refreshed) Flicks (Help eyes move so that image fall on fovea again) VOLUNTARY Pursuits (Slow movements to ‘track’ objects) Saccades (Fast movements to ‘jump’ to objects)
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INVOLUNTARY MOVEMENTS
DASHED = TREMORS/ DRIFTS SOLID = FLICKS
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VOLUNTARY MOVEMENTS PURSUITS SACCADES To ‘follow’ objects
What we usually test SACCADES To ‘rapidly’ shift gaze to an object of interest
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THE SUPERIOR COLLICULI
Jack of all trades Help in involuntary tracking Help in voluntary tracking Even if the visual cortex is kaput, these help turn the head in direction of ‘interest’
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NUCLEAR LEVEL CONTROL Co-ordinate eye movements -Between eyes*
-Eyes and ears -Eyes and neck Mostly via Superior colliculus*
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VOLUNTARY MOVEMENTS Pursuits Saccades
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EXTRAOCULAR MOVEMENTS
ROTATIONAL MOVEMENTS X Y Z
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PURSUITS (also applies to saccades, but we’ll deal with those a little later)
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TERMINOLOGY DUCTIONS VERSIONS VERGENCE Examining movement of one eye
Remember it is not possible to move one eye alone! VERSIONS Movements of both eyes in the same direction VERGENCE Movements of both eyes in opposite direction
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PURSUITS: DUCTIONS
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TERMINOLOGY: DUCTIONS
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Rotation around ‘Y” axis
TORSIONAL MOVEMENTS INTORSION Inward rotation Superior Rectus & Oblique EXTORSION Outward rotation Inferior Rectus & Oblique Rotation around ‘Y” axis HELP KEEP YOUR WORLD STRAIGHT!
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PRACTICE!
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PURSUITS: VERSIONS
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TERMINOLOGY: VERSIONS
HERING’S LAW SUPRA VERSION One eye follows the other Agonist Pairs in both eyes DEXTRO VERSION LEVO VERSION These are called ‘Yoke’ muscles Both get equal impulses INFRA VERSION
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TERMINOLOGY: VERSIONS
SHERRINGTON’S LAW SUPRA VERSION The antagonist muscles to yokes… … are inhibited… DEXTRO VERSION LEVO VERSION …to allow for optimal actions… …of yoke muscles INFRA VERSION
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TORSIONAL MOVEMENTS TORSIONAL MOVEMENTS CAN ALSO BE DEFINED FOR BOTH EYES INWARD ROTAION: INCYCLOVERSION OUTWAR ROTATION: EXCYCLOVERSION
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PURSUITS: VERGENCE
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TERMINOLOGY: VERGENCE
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THE NUT CRACKER Its all good knowing Versions & Ductions
But they DO NOT tell us anything about integrity of muscle function As clinicians it is more important to know about muscle functions
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MUSCLE ACTIONS ACTIONS ARE DETERMINED BY POSITION OF EYE BALL
Primary Position: Straight ahead Secondary Positions: Left, Right, Up, Down Tertiary positions: Oblique MUSCLES, THUS, HAVE COMPLEX ACTIONS
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MUSCLE ACTIONS EYES STRAIGHT EYES U/D/L/R EYES OBLIQUE
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MUSCLE ACTIONS MUSCLES, THUS, HAVE COMPLEX ACTIONS
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MUSCLE ACTIONS THANK FULLY WE OPHTHALMOLOGISTS ARE MASTERS OF SIMPLFICATIONS →
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MUSCLE TESTING We want to know: Is the muscle Working?
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MUSCLE TESTING An amazing over-simplification Makes life easy
One muscle = Moves eye in one position only Six muscles = Six position = Cardinal positions
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MUSCLE TESTING: CARDINAL POSITIONS
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DEXTRO-CYCLO Whaa….?? To make things even simpler
Refer to eye positions with reference to where they are in relation to the straight gaze
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MUSCLE TESTING: CARDINAL POSITIONS
UP & IN UP & OUT OUT IN DOWN & OUT DOWN & IN
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THESE ARE YOKE PAIRS (ACTING IN PAIRS)
EYE MOVEMENTS THESE ARE YOKE PAIRS (ACTING IN PAIRS) RT: SR LT: IO RT: IO LT: SR UP RT UP LT RT: MR LT: LR RT: LR LT: MR LT RT RT: IR LT: SO RT: SO LT: IR UP RT DWN LT
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THE RECTUS- OBLIQUE INTRIGUE
Superior & Inferior Rectii elevate and depress an abducted eye respectively Inferior & Superior Oblique elevate and depress an adducted eye respectively
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THE RECTUS- OBLIQUE INTRIGUE
To Remember this: Minimize Angle between: Eyeball & muscle The position of the eye ball Determines muscle action
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THE RECTUS- OBLIQUE INTRIGUE
1: RECTII MUSCLES 1. Minimize Angle 23° 2. EYE ABDUCTS 3. RECTII THEN ELEVATE OR DEPRESS
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THE RECTUS- OBLIQUE INTRIGUE
2: OBLIQUE MUSCLES 51° 1. Minimize Angle 2. EYE ADDUCTS 3. OBLIQUES THEN ELEVATE OR DEPRESS
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THE RECTUS- OBLIQUE INTRIGUE
Superior & Inferior Rectii elevate and depress an abducted eye respectively Inferior & Superior Oblique elevate and depress an adducted eye respectively The eye DOES NOT have to be turned exactly 23° or 51°. Maximal abducted or adducted gaze would do
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EYE MOVEMENTS RT: SR LT: IO RT: IO LT: SR RT: MR LT: LR RT: LR LT: MR
UP RT UP LT RT: SR LT: IO RT: IO LT: SR RT LT RT: LR LT: MR RT: MR LT: LR UP RT DWN LT RT: SO LT: IR RT: IR LT: SO
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MUSCLE TESTING Wait… What about up & down gaze
As well as Straight ahead?? These movements involve more than one muscle Cardinal Positions + Straight ahead (all muscles) Up (Superior Rectus + Inferior Oblique) Down (Inferior Rectus + Superior Oblique) = 9 Diagnostic Positions of gaze
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9 DIAGNOSTIC POSITIONS OF GAZE
RT: SR LT: IO SR + IO (BE) RT: IO LT: SR RT: LR LT:MR RT: MR LT: LR ALL MUSCLES RT: SO LT: IR RT: IR LT: SO IR + SO (BE) SIX CARDINAL POSITIONS + STRAIGHT + UP + DOWN = 9 DIAGNOSTIC POSITIONS
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CLINICAL SKILL RT: SR LT: IO SR + IO (BE) RT: IO LT: SR RT: LR LT:MR
MAKE A BROAD 3 LIMBED “H”, OBSERVING THE EYE AS IT MOVES RT: SR LT: IO SR + IO (BE) RT: IO LT: SR RT: LR LT:MR RT: MR LT: LR RT: IR LT: SO IR + SO (BE) RT: SO LT:IR LIMB 1 LIMB 2 (Not very useful as can’t isolate one muscle dysfunction) LIMB 3
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CLINICAL SKILL IT does not matter how the triple limb “H” is formed as long as all directions are tested!
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EOM SKILL: PURSUITS IN PAIRS
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SACCADES
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SACCADES All of what we have done Only faster!
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EOM SKILL: SACCADES IN PAIRS
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UTILZING SACCADES & PURSUITS
Continuously follow a moving object with eyes Like the pen in the video above A ball rolling along the ground A pretty figure walking by Watching videos SACCADES Switch gaze to a point of interest rapidly, really rapidly. Like the pen and hand in the video above A cricket ball being bowled or hit Objects that pass by you as you drive Reading (changing lines) Observing paintings
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WHAT HAPPENS WHEN A MUSCLE FAILS TO FUNCTION?
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EOM PALSY The eye fails to move in the direction of muscle function
The visual axis are misaligned (‘PARALYTIC-SQUINT’) Eye turned in (adducted) = Internal squint (ESO-TROPIA) Eye turned out (abducted) = External squint (EXO-TROPIA)
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EOM PALSY The patient experiences diplopia
If the patient in an adult the diplopia is intractable (i.e. will not go away) Patients adopt a compensatory head posture to get over the diplopia To minimize misalignment of axis OR they simply close their eye If the patient is a child (< 9 years) the visual cortex will ‘adapt’ by suppressing the blurrier of the two images to negate diplopia OR They adopt a compensatory head posture to get over the diplopia
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INTERNAL SQUINT MINIMIZE MIS-ALIGMENT OF EYES TURN HEAD SO THAT THE RIGHT EYE MOVES OUT
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JUST LIKE LOOKING TO THE RIGHT
VISUAL AXIS ARE ‘RE-ALIGNED’
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OTHER WAYS OF GETTING A SQUINT
FAULT IN EITHER OF THESE MECHANISMS CAN CAUSE CHILDHOOD SQUINT EYE MOVEMENTS NORMAL CALLED ‘NON-PARALYTIC SQUINTS’
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