Which of the following is an example of Resolution acuity?

• A. Teller acuity
• B. Snellen acuity
• C. Vernier acuity
• D. ETDRS

Answer: (A)

Resolution acuity measures the smallest detail separation the visual system can distinguish. Teller acuity does this by using high-contrast gratings and observing preferential looking to determine whether the pattern is resolvable, without requiring the observer to identify or name anything. This makes it a direct measure of resolution.

In contrast, tests like Snellen or ETDRS require recognition of letters or symbols, so they assess recognition acuity. Vernier acuity probes alignment precision (a hyperacuity task), which is a different kind of spatial judgment beyond standard resolution. Hence Teller acuity is the example of resolution acuity.