During the cover-uncover test, which observation indicates a tropia is present?

• A. The eye under observation shifts fixation when the other eye is uncovered
• B. The uncovered eye moves to re-fixate on the target
• C. The patient reports diplopia
• D. The pupils dilate

Answer: (A)

The key idea is that a tropia shows up as a true, constant misalignment that becomes obvious when you alter the visual input to each eye during the test. If the eye you’re watching shifts its fixation as soon as the other eye is uncovered, it reveals that the eye cannot hold alignment on its own and must re-fixate on the target. This automatic, immediate movement is the classic sign of a manifest deviation, i.e., a tropia. Diplopia is a subjective symptom the patient reports and doesn’t by itself demonstrate a persistent misalignment seen during the test, while pupil dilation is unrelated to ocular alignment.