Which test is used to confirm a small central suppression scotoma in suspected micro ET?

• A. Color vision testing
• B. Four base-out prism test
• C. Acoustic reflex testing
• D. Stereoacuity testing

Answer: (B)

Central suppression scotomas are small areas in the central retina where input from one eye is inhibited to avoid diplopia, and they are particularly relevant in suspected microesotropia. To confirm such a tiny central suppression, you need a dissociating test that probes binocular fusion under conditions that make subtle suppression reveal itself. The four base-out prism test does exactly this: by presenting prisms that shift the images outward for each eye, it dissociates the eyes and places the retinal images in a way that exposes a hidden central suppression. If fusion fails or diplopia appears under this dissociating setup, it supports the presence of a small central suppression scotoma.

Color vision testing, acoustic reflex testing, and stereoacuity testing don’t specifically isolate and test central binocular fusion in the way this prism test does. Color vision looks at chromatic discrimination, acoustic reflexes assess auditory pathways, and stereoacuity measures depth perception, which can be affected by suppression but does not directly confirm a central suppression scotoma.