The alternate cover test is used to:

The alternate cover test is used to:

• A. Measure manifest deviations by breaking fusion and observing eye movement.
• B. Assess color vision.
• C. Evaluate accommodation amplitude.
• D. Test stereo acuity.

Answer: (A)

The alternate cover test is used to reveal and measure a manifest eye misalignment by dissociating binocular fusion. When you rapidly alternate occluding each eye while the patient fixes on a target, fusion is broken and the eyes will drift if there’s a deviation. The observed movement of the eyes as they realign indicates the size and direction of a tropia (a deviation present with both eyes open). This approach directly assesses how much misalignment exists when fusion is interrupted, which is exactly what we mean by a manifest deviation. It’s not intended for color vision, accommodation amplitude, or stereo acuity, which involve perceptual skills rather than ocular alignment under dissociation.

The alternate cover test is used to reveal and measure a manifest eye misalignment by dissociating binocular fusion. When you rapidly alternate occluding each eye while the patient fixes on a target, fusion is broken and the eyes will drift if there’s a deviation. The observed movement of the eyes as they realign indicates the size and direction of a tropia (a deviation present with both eyes open). This approach directly assesses how much misalignment exists when fusion is interrupted, which is exactly what we mean by a manifest deviation. It’s not intended for color vision, accommodation amplitude, or stereo acuity, which involve perceptual skills rather than ocular alignment under dissociation.