Test 1 Flashcards by Brehana Hawkins

Kraskin-Harmon statement

The functional origins of the extra ocular muscles are in the neck and back.

How well did you know this?

Not at all

Perfectly

What is vision?

Meaning and direction of action

How well did you know this?

Not at all

Perfectly

Why do we have 3-4 gaze redirections per second?

The image on the retina fades without movement of the eye.

How well did you know this?

Not at all

Perfectly

Integration of action and recognition

Action: moving the eyes
Recognition: knowing what you’re looking at

How well did you know this?

Not at all

Perfectly

Signs of optic neuritis:

Inflammation of CN2

pain during EOMs
may be (+)APD if retrobulbar

How well did you know this?

Not at all

Perfectly

SR origin

Superior annulus of Zinn

How well did you know this?

Not at all

Perfectly

SR insertion

Obliquely on superior sclera

How well did you know this?

Not at all

Perfectly

SR movements

Coordinated movements with levator because of shared muscle sheath

23* angle with Fick’s axis to allow for more movement than straight up

How well did you know this?

Not at all

Perfectly

IR origin

Inferior annulus of Zinn

How well did you know this?

Not at all

Perfectly

IR insertion

Oblique arc onto inferior sclera

How well did you know this?

Not at all

Perfectly

IR movement

Suspensory ligament of Lockwood

23* angle with Fick’s Y-axis for more movement than just straight down

How well did you know this?

Not at all

Perfectly

LR origin

Upper and lower limb of annulus of Zinn

Process of greater sphenoid bone

How well did you know this?

Not at all

Perfectly

LR insertion

Parallel to MR

How well did you know this?

Not at all

Perfectly

LR movement

Lateral check ligament for added support

Whitnall’s tubercle for attachment to lateral wall

Rotation about the Z axis

How well did you know this?

Not at all

Perfectly

MR origin

Upper and lower Annulus of Zinn

Optic nerve sheath

How well did you know this?

Not at all

Perfectly

MR insertion

Vertical line spanning horizontal plane of eye

Closest muscle to limbus

How well did you know this?

Not at all

Perfectly

MR movement

Medial check ligament attaches muscle to medial orbital wall

How well did you know this?

Not at all

Perfectly

What is the Spiral of Tilleaux?

Spiral around limbus

How well did you know this?

Not at all

Perfectly

SO anatomical origin

Lesser sphenoid wing

How well did you know this?

Not at all

Perfectly

SO physiological origin

Cartilaginous trochlea, superior medial orbital wall

Muscle ends BEFORE trochlea (muscle tendon passes through though)

How well did you know this?

Not at all

Perfectly

SO insertion

Lateral posterior globe

How well did you know this?

Not at all

Perfectly

What happens during SO tendon flexion when the eye rotates 36 deg outward and is perpendicular to the deflection tendon?

Intorsion

How well did you know this?

Not at all

Perfectly

What happens during SO tendon flexion when the eye moves 54 deg inward, matching the line of sight to the tendon angle?

Depression

How well did you know this?

Not at all

Perfectly

Which is the only EOM to originate in the anterior orbit?

The IO

How well did you know this?

Not at all

Perfectly

IO origin

Maxillary bone inferior to nasolacrimal fossa

IO insertion

Posterior-lateral globe, inferiorly Below anterior-posterior horizontal plane

The angle the IO has with the visual axis

51 deg

Where the center of the muscle or tendon first touches the globe

Tangential point

Why is the tangential point not fixed?

It moves. | It changes when the muscle contracts or relaxes, and the eye moves.

The arc formed between the tangential point and the center of the insertion on the sclera

Arc of contact

Why does the arc of contact vary in length?

With muscle contracture, the arc length varies.

What is determined by a tangential point and the center of rotation?

The muscle plane

What does the muscle plane describe and determine?

Direction of pull of the muscles | Axis of rotation

Strabismus surgery: resection

Piece taken out | Make muscle short

What type of strabismus surgery fixes exotropia?

Resection surgery

Strabismus surgery: recession

Cut the muscle and move it backwards in hopes of weakening the muscle

What type of strabismus surgery fixes esotropia?

Recession surgery

Strabismus surgery: transposition

Changes direction of pull by LR and MR upwards

What type of surgery will fix a hyper?

Transposition surgery

What is field of fixation?

Area within which central fixation is possible by moving the eyes ONLY

Which field of fixation is larger, binocular or monocular?

Monocular because the nose doesn't get in the way

What limits the FOF?

Structures around the orbit | Refractive state of the globe

What is the reference position for ocular rotation?

Primary position

What are rotations of a single eye?

Ductions

What are rotations of both eyes?

Versions

Rotation of 12:00 towards the nose

Intorsion

Rotation of 12:00 towards the ear

Extorsion

Sherrington's Law of Reciprocal Innervation

When a muscle contracts, it's direct (w/i same eye) antagonist relaxes to an equal extent Ex. LMR and LLR

Herings Law of a Equal Innervation

Contraction of one EOM occurs with equal and simultaneous contraction of the the Contralateral agonist Ex. LIO and RSR

Positive forced duction test

The eye did not move, so we know there is a muscle or orbit problem

Negative duction test

The eye moves, so we know there is a nerve, neuromuscular junction, or brain problem.

Movement of a body in a 2D direction

Translation Commutative

Movementof a body in a 3D direction

Rotation Not commutative

Fick's X axis

Pitch

Fick's Y axis

Yaw

Fick's Z axis

Roll

Flat movement

End position can be described 3 Cartesian coordinates Cannot return to original position

Curved movement

End position cannot be described using 3 coordinates We can get back to the original position though

Ruete and Donders

Observed the cross grid with after images and discovered false torsion

What is happening with false torsion?

A different torsional position of the eye is not actually being achieved. It looks like this because curved space and a flat grid do not match.

Donder's Law

Wherever the eye lands, there's only 1 torsional position for that landing point Only one orientation can be reached by a single rotation

Listing's Law

We can figure out what the orientation that Donders was talking about actually is by measuring rotations around Listing's Plane

Listing's Plane

A theoretical plane through the equator of the globe, separating it into anterior and posterior segments

How many sequences of rotation are possible?

Fick's Eye-Fixed System

The vertical z axis is fixed in the skull

Helmholtz Eye-Fixed System

The horizontal x axis is fixed in the skull

Euler's Head-Fixed System

New orientation can be represented by rotation around a single axis at a specific angle relative to the vertical axis

Listing's Law in Helmholtz coordinates

T=-HV/2

Positive quantities for Listing's Law

Clockwise, right, and up from the patient's POV

Listing's Half-Angle Rule

Whatever the angle measure for the tilt of the LOS is, Listing's plane is rotated from its usual position by half that angle amount One-eyed situation Head at rest

Binocular extension of Litsting's law

When the eyes converge, they do so at a tilt from the primary position, angle a. The velocity plane for each eye tilts a fourth of angle a away from the normal Listing Plane 2-eyed situation Head at rest

Half Listing's Law for VOR

During head rotation, velocity plane tilts about 1/3 to 1/4 as the LOS 1-eyed situation Head in motion

What is the only EOM without a pulley?

The SO, it has the trochlea

Functional origins of EOMs

At its pulley In the neck and back (viewing system as a whole)