What distance(s) is the Feinbloom chart calibrated to?

What distance(s) is the Feinbloom chart calibrated to?

• A. Specific test distance
• B. Any distance; optotype sizes not calibrated for a specific test distance
• C. Only at 2 meters
• D. Only at 6 meters

Answer: (D)

The Feinbloom chart is designed to be read from a single, fixed distance, so that each line corresponds to a consistent angular size at that distance. This makes the measured acuity meaningful and comparable when you test at that distance. For the Feinbloom chart, that distance is 6 meters. If you used the chart from a different distance, the same letters would subtend a different visual angle, changing the difficulty and making the results inaccurate or inconsistent with standard distance acuity. So it’s calibrated for a single test distance: 6 meters. Using it at 2 meters would effectively change the difficulty, and using it at any distance would not preserve the intended calibrations.

The Feinbloom chart is designed to be read from a single, fixed distance, so that each line corresponds to a consistent angular size at that distance. This makes the measured acuity meaningful and comparable when you test at that distance. For the Feinbloom chart, that distance is 6 meters. If you used the chart from a different distance, the same letters would subtend a different visual angle, changing the difficulty and making the results inaccurate or inconsistent with standard distance acuity.

So it’s calibrated for a single test distance: 6 meters. Using it at 2 meters would effectively change the difficulty, and using it at any distance would not preserve the intended calibrations.