Question 75 of 100
(demo test)
Product Demo for COA Exam Questions
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A patient has double vision. You do the alternate cover test. As you uncover the left eye, it moves toward the patient's right side and also moves upward. Which deviation does this patient have?
This patient has an exodeviation with a right hyperdeviation. Read the test by one simple rule: the eye you uncover moves back from where it was resting. The left eye moved toward the patient's right side. For the left eye, that direction is inward, toward the nose. An eye only moves in if it was sitting out, so an exodeviation is present. The left eye also moved up, so it was sitting down.
The prefixes name the direction. Eso means in and exo means out. Hyper means up and hypo means down. A left eye that rests low can be called a left hypodeviation or a right hyperdeviation. Both names describe the same vertical mismatch. Only one choice pairs a correct vertical name with exo, so exo plus right hyper is the best answer. Note what this test cannot tell you. The alternate cover test moves the occluder back and forth so the patient cannot fuse. It measures the total deviation, which is the hidden part plus the open part. The textbook states plainly that it does not tell a tropia from a phoria. That is why the cover-uncover test is done first.
Carry one sentence into the exam room: the uncovered eye moves the opposite way from its resting position. In means it was out, out means it was in, up means it was down. Reading cover test movement is a core part of the COA ocular motility content area.
Incorrect Answers
- A. The vertical half is right, but an esodeviation would make the left eye move outward, toward the ear. This eye moved in.
- B. Both halves are wrong. The eye moved in, not out, and the left eye was sitting low, not high.
- C. Left hypo is a fair name for the vertical part, but the horizontal part is wrong. Eso does not fit an eye that moved inward.
- D. The exo half is right. The vertical half is backward, since an upward refixation means the eye rested below the target.
Testing Pearls
- The uncovered eye moves opposite its rest position: in means exo, out means eso.
- An upward refixation means the eye was hypo; a downward one means it was hyper.
- A left hypodeviation and a right hyperdeviation describe the same vertical mismatch.
- The alternate cover test measures total deviation and cannot separate tropia from phoria.
- Do the cover-uncover test first, then the alternate cover test, then add prisms to measure.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 9, Ocular Motility.
