extra ocular movements
DESCRIPTION
Extra Ocular Movements. (aka) …and you thought hyperopia was bad…. WHAT ARE WE GOING TO DO T’DAY?. Some ( very, very little ) Basics Extra Ocular Muscles Innervation Control of movements Movements Terminology Actions Testing. BASICS. The Extra Ocular Muscles. - PowerPoint PPT PresentationTRANSCRIPT
Extra Ocular Movements
(aka)…and you thought hyperopia was
bad…
WHAT ARE WE GOING TO DO T’DAY?
• Some (very, very little) Basics– Extra Ocular Muscles– Innervation
• Control of movements
• Movements– Terminology– Actions– Testing
BASICS
The Extra Ocular Muscles
The Extra Ocular Muscles -Origin
The Extra Ocular Muscles -Origin
LR
IR
SR
MR
SO
IO
Annulus
TROCHLEA
The Extra Ocular Muscles -Origin
LR
IR
SR
MR
SO
IO
TROCHLEA
The Extra Ocular Muscles -Origin
LR
SRSO
IOIR
The Extra Ocular Muscles -Origin
IR
SR
MR
SO
IO
TROCHLEA
The Extra Ocular Muscles
LR MR
SR
IR
IO
SO
The Extra Ocular Muscles
SO
SR LRMR
IO
The Extra Ocular Muscles
LR
IR
SR
MR
SO
IO
The Extra Ocular Muscles
SR
LR
MR
The Extra Ocular Muscles
23°SRIR
51°SOIO
OPTICAL AXIS
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
INNVERVATION
LR6 SO4 O3
SOME RULES
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)
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)
RULES #3
• MUSCLE ACTIONS & TESTING ARE DIFFERENT!
CONTROL OF MOVEMENTS
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)
STEP 1: Find what you want to see STEP 2: Keep your eyes fixed on it
SUPRA NUCLEAR: CONTROL MEHANISM
CONTROL MECHANISMS• INVOLUNTARY– 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)
INVOLUNTARY MOVEMENTS
DASHED = TREMORS/ DRIFTSSOLID = FLICKS
VOLUNTARY MOVEMENTS
• PURSUITS– To ‘follow’ objects– What we usually test
• SACCADES– To ‘rapidly’ shift gaze to an object of interest
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’
NUCLEAR LEVEL CONTROL
Co-ordinate eye movements -Between eyes* -Eyes and ears -Eyes and neck
Mostly via Superior colliculus*
VOLUNTARY MOVEMENTSPursuitsSaccades
EXTRAOCULAR MOVEMENTS
Y
X
Z
ROTATIONAL MOVEMENTS
PURSUITS(also applies to saccades, but we’ll deal with those a little later)
TERMINOLOGY• DUCTIONS– 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
PURSUITS: DUCTIONS
TERMINOLOGY: DUCTIONS
TORSIONAL MOVEMENTS
Rotation around ‘Y”
axis
INTORSIONInward rotationSuperior Rectus & Oblique
EXTORSIONOutward rotationInferior Rectus & Oblique
HELP KEEP YOUR WORLD STRAIGHT!
PRACTICE!
PURSUITS: VERSIONS
TERMINOLOGY: VERSIONS
INFRA VERSION
DEX
TRO
VER
SIO
N LEVO VERSIO
NSUPRA VERSION
One eye follows the other
Agonist Pairs in both eyes
These are called ‘Yoke’ muscles
Both get equal impulses
HERING’S LAW
TERMINOLOGY: VERSIONS
INFRA VERSION
DEX
TRO
VER
SIO
N LEVO VERSIO
NSUPRA VERSION
The antagonist muscles to yokes…
… are inhibited…
…to allow for optimal actions…
…of yoke muscles
SHERRINGTON’S LAW
TORSIONAL MOVEMENTS
• TORSIONAL MOVEMENTS CAN ALSO BE DEFINED FOR BOTH EYES
• INWARD ROTAION: INCYCLOVERSION
• OUTWAR ROTATION: EXCYCLOVERSION
PURSUITS: VERGENCE
TERMINOLOGY: VERGENCE
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
http://forums.studentdoctor.net/archive/index.php/t-109725.html
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
MUSCLE ACTIONS
EYES STRAIGHT EYES U/D/L/R EYES OBLIQUE
MUSCLE ACTIONS
• MUSCLES, THUS, HAVE COMPLEX ACTIONS
MUSCLE ACTIONS
• THANK FULLY WE OPHTHALMOLOGISTS ARE MASTERS OF SIMPLFICATIONS
→
MUSCLE TESTINGWe want to know: Is the muscle Working?
MUSCLE TESTING• An amazing over-simplification
• Makes life easy
• One muscle = Moves eye in one position only
• Six muscles = Six position = Cardinal positions
MUSCLE TESTING: CARDINAL POSITIONS
DEXTRO-CYCLO Whaa….??
• To make things even simpler
• Refer to eye positions with reference to where they are in relation to the straight gaze
MUSCLE TESTING: CARDINAL POSITIONS
OUT IN
DOWN & OUT DOWN & IN
UP & OUT UP & IN
EYE MOVEMENTS
RT: SR LT: IO
RT: IO LT: SR
RT: MR LT: LR
RT: SO LT: IR
RT: IR LT: SO
RT: LR LT: MR
THESE ARE YOKE PAIRS (ACTING IN PAIRS)
UP RT
RT
UP LT
LT
DWN LTUP RT
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 RECTUS- OBLIQUE INTRIGUE
• To Remember this:• Minimize Angle between:– Eyeball & muscle
• The position of the eye ball– Determines muscle action
THE RECTUS- OBLIQUE INTRIGUE
1. Minimize Angle 23°
1: RECTII MUSCLES
2. EYE ABDUCTS
3. RECTII THEN ELEVATE OR
DEPRESS
THE RECTUS- OBLIQUE INTRIGUE
1. Minimize Angle
2: OBLIQUE MUSCLES
2. EYE ADDUCTS
3. OBLIQUES THEN ELEVATE OR
DEPRESS
51°
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
EYE MOVEMENTS
RT: SR LT: IO
RT: IO LT: SR
RT: MR LT: LR
RT: SO LT: IR
RT: IR LT: SO
RT: LR LT: MR
UP RT
RT
UP LT
LT
DWN LTUP RT
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
9 DIAGNOSTIC POSITIONS OF GAZE
SIX CARDINAL POSITIONS + STRAIGHT + UP + DOWN= 9 DIAGNOSTIC POSITIONS
ALL MUSCLES
SR + IO (BE)
IR + SO (BE)
RT: SR LT: IO
RT: LR LT:MR
RT: IR LT: SO
RT: IO LT: SR
RT: MR LT: LR
RT: SO LT: IR
CLINICAL SKILL
RT: LR LT:MR
RT: SR LT: IO
RT: IR LT: SO
SR + IO (BE)
IR + SO (BE)
RT: IO LT: SR
RT: SO LT:IR
MAKE A BROAD 3 LIMBED “H”, OBSERVING THE EYE AS IT MOVES
RT: MR LT: LR
LIMB 1 LIMB 2(Not very useful as can’t isolate one
muscle dysfunction)
LIMB 3
CLINICAL SKILL
• IT does not matter how the triple limb “H” is formed as long as all directions are tested!
EOM SKILL: PURSUITS IN PAIRS
SACCADES
SACCADES
• All of what we have done
• Only faster!
EOM SKILL: SACCADES IN PAIRS
UTILZING SACCADES & PURSUITS• 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
WHAT HAPPENS WHEN A MUSCLE FAILS TO FUNCTION?
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)
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
INTERNAL SQUINT
MINIMIZE MIS-ALIGMENT OF EYES
TURN HEAD SO THAT THE RIGHT EYE MOVES OUT
JUST LIKE LOOKING TO THE RIGHT
VISUAL AXIS ARE ‘RE-ALIGNED’
OTHER WAYS OF GETTING A SQUINTFAULT IN EITHER OF THESE MECHANISMS
CAN CAUSE CHILDHOOD SQUINTEYE MOVEMENTS NORMALCALLED ‘NON-PARALYTIC SQUINTS’