COA Ocular Motility and Alignment 2

Question 1

During the cover-uncover test, the examiner covers the right eye. The left eye moves outward (temporally) to pick up fixation. This finding MOST likely indicates:

Accepted Answer

Left esotropia

Answer

If the uncovered (left) eye moves outward when the right eye is covered, the left eye was turned inward (esotropia) before coverage. The outward refixation movement reveals a manifest inward deviation of the left eye.

Question 2

In ocular motility testing using the H pattern (nine cardinal positions of gaze), which muscle is being evaluated when the patient looks to the right and UP?

Accepted Answer

Right superior rectus (SR) and left inferior oblique (IO)

Answer

In right and up gaze, the right superior rectus is the primary elevator and the left inferior oblique is the primary elevator of the fellow eye in that conjugate gaze position. The superior rectus and inferior oblique are yoke muscles (Hering's law) for upgaze.

Question 3

A patient reports diplopia that is WORSE when looking down and to the left. Which cranial nerve palsy is MOST likely?

Accepted Answer

Right CN IV (trochlear) palsy

Answer

The right superior oblique (CN IV) primarily depresses and intorts the eye. Diplopia that worsens in downgaze (especially when adducted, i.e., looking left with the right eye) is the classic presentation of a right CN IV palsy.

Question 4

The Hirschberg test estimates the angle of strabismus by observing corneal light reflections. If the corneal reflex appears at the pupil margin of the right eye and centered in the left eye, approximately how many prism diopters of deviation is estimated?

Accepted Answer

15–20 prism diopters

Answer

In the Hirschberg test, a decentered corneal light reflex at the pupil margin corresponds to approximately 15 prism diopters (pd) of deviation. Each millimeter of decentration equals approximately 15 pd (some sources use 7° or 22 pd/mm depending on reference).

Question 5

Which test best evaluates for a latent deviation (phoria) that is only revealed when binocular fusion is disrupted?

Accepted Answer

Alternate cover test

Answer

The alternate cover test rapidly moves the occluder from eye to eye, preventing fusion and revealing both manifest (tropia) and latent (phoria) deviations. The cover-uncover test reveals only manifest deviations.

COA - Certified Ophthalmic Assistant Practice Test

COA - Certified Ophthalmic Assistant Practice Test

COA Ocular Motility and Alignment 2