Would you like a simple way to eliminate the 26% over and under correction?
The 1862 Snellen test is inherently flawed due to its relative imprecision and inconsistency.
http://www.dyop.info/documents/Acuity_Comparison.pdf
The increased precision and consistency of the Dyop test eliminates those problems.
www.dyopacuity.com
Please contact me so that we can provide you with a complimentary copy of the Dyop test for your research.
Allan Hytowitz