Which of the following tests is NOT performed under monocular conditions?

• A. MEM
• B. Visuoscopy
• C. Angle lambda
• D. Haidinger’s brush

Answer: (A)

A key idea here is which tests are done with one eye patched (monocular) versus those that rely on both eyes being open (binocular) to interpret reflexes and fixation.

Angle lambda is a binocular assessment. It depends on observing how the visual axes of the two eyes align while both eyes are fixating on a target, usually by noting the position of the corneal reflex or Purkinje images. If one eye is patched, the normal binocular alignment changes, so this measurement wouldn’t reflect the true lambda angle.

By contrast, the other tests are typically performed with the non-tested eye occluded. MEM retinoscopy estimates accommodation with the eye being tested and the fellow eye covered; visuoscopy maps fixation with the tested eye while the other is covered; Haidinger’s brush is a macular function test done with the eye open but using a setup that essentially treats it as a monocular test.

So the test that isn’t performed under monocular conditions is the angle lambda, because it requires binocular viewing to assess the natural alignment of the visual axes.