Which term describes when patients with heterophoria cannot obtain fusion and images jump over each other?

• A. Horror fusionis
• B. Diplopia
• C. Suppression
• D. Vertical diplopia

Answer: (A)

When fusion cannot be maintained in a heterophoric patient, the brain may struggle so much with merging the two images that the perceptual experience is described as horror fusionis. In this phenomenon, the images don’t simply appear as two separate pictures; they tend to jump or swap positions as the visual system attempts (and fails) to fuse them. This specific term captures the unusual, almost shocking sense of displacement that occurs during attempted fusion.

Diplopia would be the general outcome of not fusing—seeing two images—but the situation described here emphasizes the abrupt, jumping appearance of the images, which is why horror fusionis is the best fit. Suppression is when the brain ignores one eye to avoid diplopia, so it wouldn’t produce two visible images. Vertical diplopia is a form of double vision due to a vertical misalignment, but it doesn’t describe the jumping phenomenon.