The MNREAD story

The MNREAD Reading Acuity Chart was developed in the Minnesota Laboratory for Low-Vision Research at the University of Minnesota with funding from NIH. Gordon Legge and Steve Mansfield have led the ongoing development with the collaboration of many students and colleagues.

In 1989 Gordon and colleagues created the Minnesota Low-Vision Reading Test to measure the maximum reading speed of people with low vision.1 The test was implemented on IBM PC computers and named MNread in recognition of its origin in Minnesota (later, the spelling switched to MNREAD). In the test, short sentences with 4 lines of 13 characters in a fixed-width font similar to Courier were displayed in large print (6 degrees) on a computer display for a pre-set duration. The subject read the sentence aloud. In a sequence of trials, the experimenter reduced the presentation time until the subject was unable to complete the sentence. Reading speed was then calculated as the number of words read correctly divided by the presentation time.

In 1993, a hard copy version of this test was created using printed cards rather than a computer display.2 Officially called "printed cards for measuring low-vision reading performance", the cards were dubbed the MNREAD printed cards. 

Next, we proceeded to develop the reading acuity charts composed of sentences with a series of print sizes, but still using Courier, a fixed-width font. We presented the MNREAD Acuity Charts at the OSA Noninvasive Assessment of the Visual System conference in Monterey in 1993.3 At that meeting, we were persuaded to consider making charts that used a proportionally spaced font, such as Times-Roman, that would be more representative of the print found in everyday reading material. This directly led to the development of the MNREAD Acuity Charts in their current form. 

Using a proportionally spaced font required a change in the MNREAD sentence format. Standard MNREAD sentences now contain 60 characters which are printed on three text lines with a precisely defined layout. During the development of the new charts, we had the opportunity to compare reading performance between the different font styles (Courier and Times Roman) used on the old and new versions.4 For this study we needed to formalize the derivation of the critical print size (CPS). This led to the testing of various curve-fitting algorithms for estimating the CPS.

In 1994 the University of Minnesota licensed Lighthouse Low-Vision products to market and distribute the MNREAD Acuity charts. The charts are currently manufactured and sold by Precision Vision Inc., (Woodstock, IL) through a licensing agreement with the University of Minnesota.

MNREAD charts have been developed in several languages in addition to English. Chart development in a new language requires creation of test sentences meeting the demanding linguistic and typographic design specifications of MNREAD, followed by pilot testing of the new materials with groups of subjects. As of 2020, MNREAD charts have been developed in Spanish, French, Italian, Portuguese, Greek, Turkish, German, Dutch and Japanese. Development continues in several other languages.

In 2017, an iPad version of MNREAD was released and is available through the Apple App Store. In a study we compared measurements made on the MNREAD chart and the iPad version of MNREAD.5

  1. Legge, G.E., Ross, J.A., Luebker, A., & LaMay, J.M. (1989). Psychophysics of reading. VIII. The Minnesota low-vision reading test. Optometry & Vision Science, 66(12), 843-853. (abstract) (PDF)
  2. Ahn, S.J., Legge, G.E., & Luebker, A. (1995). Printed cards for measuring low-vision reading speed. Vision Research, 35(13), 1939-1944. (article) (PDF)
  3. Mansfield, J.S., Ahn, S., Legge, G.E., & Luebker, A. (1993). A new reading-acuity chart for normal and low vision. Ophthalmic and Visual Optics/Noninvasive Assessment of the Visual System Technical Digest, 3, 232-235.
  4. Mansfield, J.S., Legge, G.E., & Bane, M.C. (1996). Psychophysics of reading. XV. Font effects in normal and low vision. Investigative Ophthalmology & Visual Science, 37(8), 1492-1501. (abstract) (PDF)
  5. Calabrèse, A., To, L., He, Y., Berkholtz, E., Rafian, P. & Legge, G.E. (2018). Comparing performance on the MNREAD iPad app with the MNREAD acuity chart. Journal of Vision, 18(1): 8. (article) (PDF)