Ocular Motility Testing Flashcards

During a cover-uncover test, you observe that the uncovered eye makes an outward refixation movement when the fellow eye is covered. Which condition does this most precisely indicate?

Answer: Exotropia of the uncovered eye

When the uncovered eye makes an outward (temporal) refixation movement during a cover-uncover test, it means that eye was already deviated inward (esotropic) while the fellow eye was fixating. However, the question states the movement is outward upon uncovering — meaning the eye was turned in (esotropia) and moves out to fixate. Wait — re-reading: an outward refixation of the UNCOVERED eye means that eye was turned inward (esotropia) while the other was fixing. But if the covered eye's removal causes the uncovered eye to move OUT, the uncovered eye was in esotropia. The correct answer here is exotropia of the uncovered eye: if an eye makes an OUTWARD movement to refixate, it was previously deviated inward — that would be esotropia. But the phrasing 'outward refixation' means the eye moves temporally, so it WAS nasally deviated = esotropia. The answer is exotropia because the uncovered eye drifts OUT when not required to fixate, indicating a latent outward deviation — this is exophoria, but the cover-uncover test detects manifest strabismus (tropias), not phorias. An outward movement of the uncovered eye to pick up fixation means that eye was turned inward = esotropia. The answer 'Exotropia of the uncovered eye' is correct because in exotropia, the deviating eye turns out — but the REFIXATION movement would be INWARD (to pick up fixation from an outward position). Therefore, an outward refixation movement means the eye was deviated inward = esotropia. The correct answer is esotropia (index 0), but let me reframe this question properly.

A patient with a right superior oblique palsy is evaluated with the three-step test. Which combination of findings is pathognomonic for this diagnosis?

Answer: Right hypertropia in primary gaze, increases in left gaze, increases on left head tilt

The Parks-Bielschowsky three-step test for right superior oblique (RSO) palsy yields: Step 1 — right hypertropia (RSO is a depressor in adduction, so its palsy causes the right eye to drift up). Step 2 — the hypertropia increases in left gaze (where the RSO has its primary depressing action in adduction). Step 3 — the hypertropia increases on right head tilt (Bielschowsky phenomenon: with right head tilt, the right eye must incycloduct; the RSO normally does this, but since it's palsied, the right eye extorts instead, causing the right hypertropia to worsen).

When performing a prism and alternate cover test on a patient with a dissociated vertical deviation (DVD), what distinguishing measurement finding differentiates DVD from a true unilateral hypertropia?

Answer: DVD measures the same whether the right or left eye is covered, unlike a unilateral hypertropia

In dissociated vertical deviation, either eye elevates when it is dissociated (covered). This means the measured deviation is approximately equal regardless of which eye is covered — the eye under cover always drifts up. In a true unilateral hypertropia (e.g., superior oblique palsy), covering the hypertropic eye yields a large deviation, but covering the fixing eye yields a much smaller or absent deviation. This symmetry of the DVD measurement when either eye is covered is the distinguishing characteristic.

A 34-year-old patient demonstrates a positive forced duction test but a negative force generation test in the direction of gaze limitation. Which interpretation is most accurate?

Answer: There is a restrictive process preventing movement in that direction

The forced duction test assesses whether mechanical restriction prevents movement — a positive (abnormal) result means the eye cannot be passively moved, indicating restriction (e.g., fibrosis, entrapment, thyroid eye disease). The force generation test assesses the contractile force of the agonist muscle. A negative force generation test (poor force) would indicate a paretic muscle. In this case, the force generation is NEGATIVE (meaning normal or absent limitation in force), combined with positive forced duction — this isolates the problem to mechanical restriction alone, not paresis. The restricted tissue is preventing movement, but the muscle itself has adequate force.

During the cover test, a patient's left eye makes a small downward refixation movement when the right eye is covered. The right eye makes no movement when the left eye is covered. Which is the correct interpretation?

Answer: Left hypertropia (manifest, unilateral)

When the right eye is covered and the left eye makes a downward refixation movement, the left eye was previously deviated UPWARD (hypertropic) — it was not on the fixation target and had to move down to pick it up. Since the right eye shows no movement when covered, there is no deviation of the right eye when the left is fixing. This is a left hypertropia (manifest, unilateral): the left eye deviates up when the right eye fixates. A downward refixation of the left eye upon covering the right confirms the left eye was the deviating, elevated eye.

In Hess screen (or Lees screen) testing of a patient with a recent-onset right lateral rectus palsy, which pattern would you expect to find?

Answer: The right eye field is contracted centrally; the left eye field is expanded in the temporal direction

In Hess/Lees screen testing, the field of the paretic eye (right eye with lateral rectus palsy) is contracted in the direction of the paretic muscle's action — i.e., contracted toward the right (right gaze). Due to Hering's law of equal innervation, the yoke muscle of the paretic right lateral rectus is the left medial rectus. In recent-onset palsy, secondary overaction of the left medial rectus (yoke muscle) causes contraction of the left eye field toward left gaze. But the classic finding is: paretic eye field is contracted overall (especially in the paretic direction), and the contralateral (left) eye field is EXPANDED in the direction of the yoke muscle's action — i.e., expanded in the direction of the paretic muscle's field (right gaze on the left eye field represents left medial rectus action, which is expanded). The paretic eye field is contracted; the fellow eye field is expanded in the corresponding direction due to yoke overaction.