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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.
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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
The Extra Ocular Muscles -Origin TROCHLEA SR SO Annulus LR MR IR IO
The Extra Ocular Muscles -Origin TROCHLEA SR SO LR MR 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
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 & TESTINGARE DIFFERENT!
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
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/ DRIFTS SOLID = 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*
EXTRAOCULAR MOVEMENTS ROTATIONAL MOVEMENTS X Y Z
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
TORSIONAL MOVEMENTS INTORSION Inward rotation Superior Rectus & Oblique EXTORSION Outward rotation Inferior Rectus & Oblique Rotation around ‘Y” axis HELP KEEP YOUR WORLD STRAIGHT!
TERMINOLOGY: VERSIONS HERING’S LAW SUPRA VERSION Agonist Pairs in both eyes One eye follows the other LEVO VERSION DEXTRO VERSION These are called ‘Yoke’ muscles Both get equal impulses INFRA VERSION
TERMINOLOGY: VERSIONS SHERRINGTON’S LAW SUPRA VERSION … are inhibited… The antagonist muscles to yokes… LEVO VERSION DEXTRO 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
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
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 →