Suppression is typically caused by fusional stress such as tropias and can also be caused by what condition?

• A. Anisometropia only
• B. Fusional stress only
• C. Both fusional stress and anisometropia
• D. Neither

Answer: (C)

Suppression happens when the brain chooses one eye’s input to avoid conflicting information between the eyes. Fusional stress, like a tropia, creates misalignment that the visual system can’t fuse, so it suppresses input from one eye to prevent double vision. Anisometropia—when the two eyes have different refractive powers—also disrupts fusion because the images differ in clarity or size; the brain tends to rely on the clearer image and suppresses the blurrier one to maintain single, stable vision. This can occur even without a noticeable misalignment, and if not addressed, can lead to reduced vision in the suppressed eye. So suppression can be caused by both fusional stress and anisometropia.