Which statement best describes the alternate cover test?

Which statement best describes the alternate cover test?

• A. It measures manifest deviations by breaking fusion and observing eye movement.
• B. It measures refractive error.
• C. It assesses stereoacuity.
• D. It tests color vision.

Answer: (A)

Alternate cover testing is used to reveal a manifest eye deviation by breaking binocular fusion and watching how the eyes move to re-fixate. By alternately covering each eye, fusion is disrupted so the eyes can no longer align to maintain single vision. If a tropia is present, you’ll see an obvious movement of the eye that would normally fixate as the cover switches, indicating a true, observable misalignment. This test is specifically about detecting and characterizing a deviation that is always present when fusion is disrupted, not about refractive errors, stereoacuity, or color vision, which are assessed with other, separate tests.

Alternate cover testing is used to reveal a manifest eye deviation by breaking binocular fusion and watching how the eyes move to re-fixate. By alternately covering each eye, fusion is disrupted so the eyes can no longer align to maintain single vision. If a tropia is present, you’ll see an obvious movement of the eye that would normally fixate as the cover switches, indicating a true, observable misalignment. This test is specifically about detecting and characterizing a deviation that is always present when fusion is disrupted, not about refractive errors, stereoacuity, or color vision, which are assessed with other, separate tests.