The size of an average finger corresponds to which letter size?

The size of an average finger corresponds to which letter size?

• A. 100 Foot Letter
• B. 200 Foot Letter
• C. 700 Foot Letter
• D. 400 Foot Letter

Answer: (B)

In functional vision assessment, we use practical comparisons when letters can’t be read. The size of an average finger corresponds to a 200-foot letter because a finger held at a typical near distance subtends a retinal angle similar to the angle a very large letter would at the distance a person with normal acuity would need to read it. This makes the finger a convenient proxy for estimating acuity and for planning magnification and daily tasks. It’s an approximate, widely used reference, and the other large-letter sizes aren’t the standard finger-size equivalent.

In functional vision assessment, we use practical comparisons when letters can’t be read. The size of an average finger corresponds to a 200-foot letter because a finger held at a typical near distance subtends a retinal angle similar to the angle a very large letter would at the distance a person with normal acuity would need to read it. This makes the finger a convenient proxy for estimating acuity and for planning magnification and daily tasks. It’s an approximate, widely used reference, and the other large-letter sizes aren’t the standard finger-size equivalent.