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 TROCHLEA SR SO Annulus LR MR IR IO

The Extra Ocular Muscles -Origin TROCHLEA SR SO MR LR IR IO

The Extra Ocular Muscles -Origin SR SO LR IO IR

The Extra Ocular Muscles -Origin SR TROCHLEA SO MR IO IR

The Extra Ocular Muscles SR SO MR LR IR IO

The Extra Ocular Muscles IO SO MR LR SR

The Extra Ocular Muscles SR SO LR MR IO IR

The Extra Ocular Muscles MR SR LR

The Extra Ocular Muscles SO IO 51° 23° SR IR 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 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)

INVOLUNTARY MOVEMENTS DASHED = TREMORS/ DRIFTS SOLID = FLICKS

VOLUNTARY MOVEMENTS PURSUITS SACCADES 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 MOVEMENTS Pursuits Saccades

EXTRAOCULAR MOVEMENTS ROTATIONAL MOVEMENTS X Y Z

PURSUITS (also applies to saccades, but we’ll deal with those a little later)

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

PURSUITS: DUCTIONS

TERMINOLOGY: DUCTIONS

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!

PRACTICE!

PURSUITS: VERSIONS

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

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

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 TESTING We 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 UP & IN UP & OUT OUT IN DOWN & OUT DOWN & IN

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

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: RECTII MUSCLES 1. Minimize Angle 23° 2. EYE ABDUCTS 3. RECTII THEN ELEVATE OR DEPRESS

THE RECTUS- OBLIQUE INTRIGUE 2: OBLIQUE MUSCLES 51° 1. Minimize Angle 2. EYE ADDUCTS 3. OBLIQUES THEN ELEVATE OR DEPRESS

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: 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

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 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

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

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 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 SQUINT FAULT IN EITHER OF THESE MECHANISMS CAN CAUSE CHILDHOOD SQUINT EYE MOVEMENTS NORMAL CALLED ‘NON-PARALYTIC SQUINTS’