Double vision on looking to the right (30/1700)

A young man complains of double vision on seeing to the right. Which nerve is most likely to be
involved?
a. Left abducens
b. Right abducens
c. Left trochlear
d. Right trochlear
e. Right oculomotor

























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answer: B> right abducens nerve palsy : diplopia and convergent squint

• binocular diplopia (occurs with both eyes open, eliminated when you cover one eye)

strabismus, CN palsy (III, IV, VI) secondary to ischemia, DM, tumor, trauma, myasthenia gravis, muscle restriction/entrapment, thyroid ophthalmopathy, INO secondary to multiple sclerosis, brainstem infarct

• monocular diplopia (remains with occlusion of unaffected eye)

-        refractive error, strands of mucus in tear film, keratoconus, cataracts, dislocated lens, peripheral iridotomy

Extraocular Muscle Innervations

LR6 SO4 AE3

1.      Lateral Rectus via CN VI (abducens) Double vision occurs when people look toward the side of the affected eye.

2.      Superior Oblique via CN IV (trochlear) The affected eye cannot turn inward and down

3.      All Else via CN III (oculomotor) (superior, medial, and inferior rectus, inferior oblique) The affected eye turns outward when the unaffected eye looks straight ahead, causing double vision. The affected eye can move only to the middle when looking inward and cannot move up and down. Because the 3rd cranial nerve also raises the eyelids and controls the pupils, the eyelid droops, and the pupil may be widened (dilated) and may not narrow (constrict) in response to light.