Free COA Ocular Motility and Pupils Questions and Answers — Questions and Answers
Question 1: A patient is being evaluated for double vision. During motility testing, the patient is unable to abduct their left eye (turn it outward). This limitation is most likely due to a weakness of which muscle and a palsy of which cranial nerve?
- Medial Rectus, CN III
- Lateral Rectus, CN VI (Correct answer)
- Superior Oblique, CN IV
- Inferior Oblique, CN III
Correct answer: Lateral Rectus, CN VI
Abduction, or moving the eye outward away from the nose, is the primary action of the lateral rectus muscle. The lateral rectus muscle is solely innervated by the sixth cranial nerve (CN VI), also known as the abducens nerve.
Question 2: When evaluating a patient's eye movements in the cardinal positions of gaze, which pair of muscles works together (as yoke muscles) to move the eyes down and to the left?
- Left Superior Rectus and Right Inferior Oblique
- Left Lateral Rectus and Right Medial Rectus
- Left Inferior Rectus and Right Superior Oblique (Correct answer)
- Left Superior Oblique and Right Inferior Rectus
Correct answer: Left Inferior Rectus and Right Superior Oblique
Yoke muscles are pairs of muscles in opposite eyes that work together to produce conjugate eye movements. To look down and to the left, the left eye's primary depressor in that position (left inferior rectus) and the right eye's primary depressor in that position (right superior oblique) must contract simultaneously.
Question 3: During a swinging flashlight test, an ophthalmic assistant observes that the patient's right pupil dilates when the light is moved from the left eye to the right eye. Which of the following does this finding indicate?
- Physiologic anisocoria
- A left oculomotor nerve palsy
- A right efferent pupillary defect
- A right afferent pupillary defect (APD) (Correct answer)
Correct answer: A right afferent pupillary defect (APD)
The swinging flashlight test is used to detect a relative afferent pupillary defect (RAPD or APD), also known as a Marcus Gunn pupil. This defect indicates a problem with the afferent pathway (optic nerve). When light is swung from the normal eye to the affected eye, the affected pupil receives a weaker signal to constrict and will paradoxically dilate.
Question 4: During a cover-uncover test on a new patient, the assistant covers the patient's right eye. The uncovered left eye then moves inward (nasally) to pick up fixation. This finding indicates the presence of a:
- Left Exotropia (Correct answer)
- Left Esotropia
- Right Hypertropia
- Right Esophoria
Correct answer: Left Exotropia
The cover-uncover test is used to detect a manifest strabismus (tropia). If the uncovered eye moves to take up fixation when the other eye is covered, a tropia is present in that uncovered eye. Since the left eye was initially deviated outward (exo-) and had to move inward to fixate, the patient has a left exotropia.
Question 5: What term is used to describe the rhythmic, involuntary, back-and-forth movement of the eyes?
- Duction
- Nystagmus (Correct answer)
- Strabismus
- Version
Correct answer: Nystagmus
Nystagmus is the medical term for rapid, involuntary, and repetitive eye movements. These movements can be side-to-side (horizontal), up-and-down (vertical), or rotary. Duction, version, and strabismus all relate to voluntary eye alignment and movement, not involuntary oscillations.
Question 6: In the common pupillary examination acronym PERRLA, what does the 'A' represent?
- Afferent
- Anisocoria
- Accommodation (Correct answer)
- Adduction
Correct answer: Accommodation
PERRLA stands for Pupils Equal, Round, Reactive to Light and Accommodation. The 'A' refers to accommodation, which is the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies. This is tested by having the patient shift focus from a distant object to a near object, which should cause pupillary constriction.
Free COA Ocular Motility and Pupils Questions and Answers
A patient is being evaluated for double vision.
During motility testing, the patient is unable to abduct their left eye (turn it outward).
This limitation is most likely due to a weakness of which muscle and a palsy of which cranial nerve?