Eye Movements Flashcards
Importance of eye movements
- the eyes move to initiate and maintain fixation by directing the line of sight
- important to keep image on the retina
- both eyes should get image at the same time
- important for following objects
Listing Plane
- imaginary coronal plane through the center of the globe
- globe rotates on the axis of Fick
X,Y, and Z Axis
X-eye rotates up and down
Y-torsional rotations. top of the eye rotates clockwise or counter clockwise
Z-eye rotates left and right
Duction
- movement of one eye around the axes of fick
- monocular
- close one eye and have one eye look in all the directions
Version
- binocular
- simultaneous and conjugate movement of both eyes
Torsion
Twist of the eye clockwise of counter clockwise
- intorsion-top of the eye rotates towards nose
- Extorsion-top of the eye rotates away from nose
Conjugate eye movement
- binocular
- visual axis of both eyes are in the same direction to maintain fixation with both eyes.
Vergence
- disconjugate eye movement
- visual axes rotate in opposite directions
- convergence-both rotate in
- divergence-both rotate out
Extraocular muscles numbers
EOM
- 4 recti muscles
- 2 oblique muscles
- FOR EACH EYE
Horizontal recti muscles
- in primary gaze, horizontal movement around Z axis
- medial and lateral
Medial Rectus
- moves the eye to the nose
- adduction
- innervated by oculomotor nerve
- inserts 5.5mm from nasal limbus
Lateral Rectus
- Moves the eye away from the nose
- aBduction
- innervated by abducent nerve
- inserts 6.9mm from temporal limbus
Vertical Recti
- still about Z axis
- superior and inferior rectus
Superior rectus
- move eye up
- elevation
- secondary-intorsion. tertiary-aDduction
- oculomotor nerve
- 7.7mm from superior limbus
Inferior Rectus
-moves eye down
-depression
secondary-extorsion. tertiary-aDduction
-oculomotor nerve
-6.5mm from inferior limbus
Medial and Lateral walls
- 45 degrees of eachother
- orbital axis if 23 degrees of the two walls
- in primary gaze, the orbital axis is at 23 degrees of the visual axis
Oblique Muscles
- insert behind equator at 51 degree angle with the visual axis
- superior oblique and inferior oblique
Superior oblique
- intorsion
- secondary-depression. tertiary-aBduction
- trochlear nerve
- passes through trochlea on medial walls and reflects back to the posterior quadrant
Inferior oblique
- extorsion
- secondary-elevation. tertiary-aBduction
- oculomotor nerve
- originates at small depression on orbital floor. inserts in posterior lower temporal quadrant close to the macula
diagnostic positions of gaze
- 6 cardinal points
- 3 other points in primary position, upgaze, and downgaze (6,1,5)
- cardinal points represent the points in which one muscle is responsible for the movement (2,3,4,7,8,9)
- Diagnostic positions are ones where deviations are measured (1-9)
Agonist-antagonist
- pair of muscles in the SAME eye that move the eye in opposite directions
- medial and lateral rectus
Synergist muscle
- muscles in the SAME eye that move the eye in the same direction
- inferior oblique and superior rectus
Yoke Muscles
- pair of muscles ONE IN EACH EYE that produce conjugate eye movements
- right inferior oblique and left superior rectus
Sherrington law of reciprocal innervation
-increased innervation to one muscle is accompanied by a reciprocal decreased innervation to its antagonist in the same eye.
Hering law of equal innervation
- during conjugate eye movements, equal and simultaneous innervations flow to yoked muscles.
- helpful to see palsy because the yoke muscle in other eye will overreact
Evaluation tid bits
- NO GLASSES
- assess ability to maintain fixation
- dont let the patient move their head
- target should be 40cm from patient
- ease, smoothness, accuracy
- “full and smooth”
- do VERSIONS first(only duction if weird)
End point nystagmus
- involuntary oscillation of the eye when you go too far in a gaze
- beat motion
