CO Ocular Motility Evaluation & Binocular Vision Assessment 3 — Questions and Answers
Question 1: The Bielschowsky head tilt test is positive (hypertropia increases on ipsilateral head tilt) with palsy of which muscle?
- Ipsilateral inferior oblique
- Ipsilateral superior oblique (Correct answer)
- Contralateral superior rectus
- Ipsilateral superior rectus
Correct answer: Ipsilateral superior oblique
On ipsilateral head tilt, the ipsilateral superior oblique and superior rectus are stimulated; if the superior oblique is paretic, the superior rectus acts unopposed causing hypertropia.
Question 2: Which finding on prism alternate cover test (PACT) suggests a restrictive etiology rather than a paretic one?
- Comitant deviation in all gazes
- Incomitance with larger deviation in the field of action of the weak muscle
- Forced duction test positive (Correct answer)
- Positive Parks step 2 (gaze direction increases deviation)
Correct answer: Forced duction test positive
A positive forced duction test (resistance to passive eye movement) confirms mechanical restriction rather than muscle paresis.
Question 3: Stereopsis of 40 seconds of arc corresponds to which clinical level?
- Gross stereopsis only
- Peripheral stereopsis
- Fine (central) stereopsis consistent with normal binocular vision (Correct answer)
- Reduced stereopsis seen in amblyopia
Correct answer: Fine (central) stereopsis consistent with normal binocular vision
40 arcsec is near-normal fine stereoacuity, consistent with intact bifoveal binocular vision.
Question 4: In Duane retraction syndrome type I, which finding is characteristic on attempted adduction?
- Globe retraction and narrowing of the palpebral fissure (Correct answer)
- Globe protrusion and widening of the palpebral fissure
- Marked limitation of abduction with normal adduction
- Upshoot only in adduction
Correct answer: Globe retraction and narrowing of the palpebral fissure
Type I Duane syndrome shows limited abduction and, on adduction, globe retraction with palpebral fissure narrowing due to co-contraction of horizontal recti.
Question 5: Which motility finding is pathognomonic for internuclear ophthalmoplegia (INO)?
- Bilateral abduction deficit
- Ipsilateral adduction deficit with contralateral abducting nystagmus (Correct answer)
- Ipsilateral abduction deficit with ipsilateral abducting nystagmus
- Upgaze palsy with convergence-retraction nystagmus
Correct answer: Ipsilateral adduction deficit with contralateral abducting nystagmus
INO results from a medial longitudinal fasciculus lesion causing ipsilateral adduction failure and dissociated nystagmus in the contralateral abducting eye.
Question 6: When measuring a vertical deviation with the prism alternate cover test, prisms are placed:
- Base-up before the hypotropic eye
- Base-down before the hypertropic eye
- Base-up before the hypertropic eye (Correct answer)
- Base-in before either eye
Correct answer: Base-up before the hypertropic eye
To neutralize a hypertropia, a base-up prism (apex down) is placed before the higher eye to redirect the image downward.
Question 7: The red glass test reveals diplopia with the red image displaced to the patient's left. The paretic muscle is most likely the:
- Right lateral rectus (Correct answer)
- Left lateral rectus
- Right medial rectus
- Left medial rectus
Correct answer: Right lateral rectus
In horizontal diplopia, the false (peripheral) image is on the side of the paretic muscle; a red glass before the right eye with the red image to the left indicates right lateral rectus palsy.
CO Ocular Motility Evaluation & Binocular Vision Assessment 3
The Bielschowsky head tilt test is positive (hypertropia increases on ipsilateral head tilt) with palsy of which muscle?