Ocular Motor Disorders

Question 1

Comitant

Answer 1

Double vision stays the same no matter where you look (as opposed to non-comitant which differs depending on where you look)

Question 2

Phoria

Answer 2

Indicates rest position of the muscles
The eyes would drift but drifting is held in check by sensory fusion
As long as the person is focusing on a target the eyes will be in alignment
Muscles are always in action- form a “balance” at a rest position

Question 3

Tropia

Answer 3

Indicates paralysis or over action of the muscles
The eye drifts even when the person is focusing on a target- may or may not have double vision
If long standing they may “suppress” the sight in one or both eyes

Question 4

Oculomotor Nerve (CN III)

Answer 4

Motor 
supplies: 
levator muscle of the eyelid
medial rectus
superior rectus
inferior rectus
inferior oblique
***CN III constricts the pupil through its parasympathetic fibers that supply the smooth muscle of the ciliary body and the sphincter of the iris.

Question 5

Complete palsy of CN III

Answer 5

Complete = Eye Down & out with Ptosis

If complete with Pupil – tumor – MRI

If complete without Pupil – watch (3 months)

If incomplete – tumor – MRI

Question 6

Trochlear Nerve (CN IV)

Answer 6

has the longest intracranial course and is the only cranial nerve that has a dorsal exit from the brainstem.
innervates:
superior oblique muscle

The long course of the fourth cranial nerve renders it particularly prone to injury from blunt head trauma or compression from changes in intracranial pressure, brain tumors, or swelling anywhere along its course.

Question 7

CN IV Palsy

Answer 7

Diplopia.
The patient may adopt an anomalous head position to avoid diplopia because torsional and vertical diplopia often improve with head tilting to the side opposite the paralyzed muscle.

Question 8

Abducens Nerve (CN VI)

Answer 8

The sixth cranial nerve enters the orbit via the superior orbital fissure to innervate:
lateral rectus muscle

Question 9

CN VI Palsy

Answer 9

Binocular horizontal diplopia that worsens with gaze toward the defective lateral rectus muscle
Primary position esotropia (eye turned in “crossed eyed”), seen in Diabetics.

Question 10

Cranial Nerve Signs

Answer 10

“Down and out” = CN 3 Palsy
“Nasal upshoot” = CN 4 Palsy
“Cross eyed” = CN 6 Palsy