Angle lambda is measured under which conditions?

Angle lambda is measured under which conditions?

• A. Monocular
• B. Binocular
• C. Both
• D. Neither

Answer: (A)

Angle lambda is the offset of the visual axis from the pupil, inferred from the position of the corneal light reflex relative to the pupil center. To obtain a stable, meaningful measure, the fixation must be monocular—one eye fixating while the other is occluded—because binocular viewing introduces vergence and fusion effects that can shift fixation and mask the true monocular offset. In binocular conditions, the reflex position can change with fusion, making the lambda value unreliable. So, the best way to measure lambda is under monocular viewing.

Angle lambda is the offset of the visual axis from the pupil, inferred from the position of the corneal light reflex relative to the pupil center. To obtain a stable, meaningful measure, the fixation must be monocular—one eye fixating while the other is occluded—because binocular viewing introduces vergence and fusion effects that can shift fixation and mask the true monocular offset. In binocular conditions, the reflex position can change with fusion, making the lambda value unreliable. So, the best way to measure lambda is under monocular viewing.