During Worth 4 Dot testing, if two red dots are seen, this indicates suppression of which eye?

• A. OD suppression
• B. OS suppression
• C. Flat fusion without suppression
• D. Diplopia

Answer: (B)

Worth 4-Dot testing uses red–green glasses and a four-dot light to uncover whether one eye is being suppressed and, if so, which one. In this setup, each eye is associated with one color: the eye wearing the red filter contributes the red dots you see, while the eye wearing the green filter contributes the green dots. If the brain suppresses one eye, its colored dots disappear from perception.

Seeing two red dots means you’re perceiving input only from the eye that sees the red dots, while the other eye’s input (the one that would see green) is being suppressed. That points to suppression of the eye receiving the green filter, i.e., the left eye in the typical arrangement. So two red dots indicate OS suppression.

If you instead saw two green dots, that would indicate OD suppression (the red-filtered eye is suppressed). Seeing all four dots typically means there’s no suppression and fusion is present. Diplopia would involve perceiving misaligned or double images rather than a single, color-limited set of dots.