The MNREAD story
In 1989 Gordon Legge and colleagues introduced the Minnesota Low-Vision Reading Test, a computer-based system for measuring reading speed.1 Short sentences with fixed format of 4 lines of 13 fixed-width characters each, are displayed in large print on computer display for a pre-set duration. The subject reads the sentence aloud. On subsequent trials, the experimenter reduces the presentation duration until the subject makes reading errors. Reading speed is given as the number of words read divided by the reading time. This test was named the MNread.
In 1993 a simplified 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 quickly dubbed the MNREAD printed cards.
Concurrently, we started to develop the first reading acuity charts using the MNREAD format. 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. Sentences now contain 60 characters which are printed onto 3 text lines. During the development of the new charts we had the unique opportunity to compare reading performance between the different font styles used on the old and new versions.4 In this study we we need to formalize the derivation of the critical print size. This lead to the testing of various line-fitting algorithms, until we finally settled upon a algorithm that works most of the time.
In 1994 the University of Minnesota licensed Lighthouse Low-Vision products to market and distribute the MNREAD Acuity charts. Since then the MNREAD charts have become a popular tool for the assessment of reading performance as a function of print size.
Charts are currently being developed in Japanese, Italian, French, Spanish, Norwegian, Danish, Swedish and Portuguese.
- Legge G.E., J.A. Ross, A. Luebker & J.M. LaMay. (1989) Psychophysics of reading. VIII. The Minnesota low-vision reading test. Optometry and Vision Science, 66, 843-853.
- Ahn, S. J. and Legge, G. E. (1995) Printed cards for measuring low-vision readng speed. Vision Research, 35, 1939-1944.
- Mansfield, J. S., Ahn, S. J., Legge, G. E., and 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, (Optical Society of America, Washington, DC., 1993.) 3, 232-235.
- Mansfield J.S., Legge G.E. and Bane M.C. (1996). Psychophysics of reading. XV. Font effects in normal and low vision. Investigative Ophthalmology & Visual Science, 37, 1492-1501.