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Eye chart fonts: Pelli and Sloan

Creative Commons License
"Pelli" and Sloan fonts by Denis G. Pelli are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

The “Pelli” and Sloan fonts are available for noncommercial research from GitHub:

The Pelli and Sloan fonts are intended for eye charts.

The Pelli font contains only 11 useful characters: 0123456789$ plus space. The characters all have the same width and height, a 5:1 aspect ratio, and a stroke width that is half the character width. The space and option-space are half the width of the other characters. The font has no descenders and the height is equal to the nominal point size requested. Adjoining characters touch. There is also a #, but its strokes are too thin. All the letters a-z and A-Z have been assigned the same dash glyph. This satisfied Microsoft Word, which was previously unable to work with this font. The font now works perfectly except for the very minor anomaly that the freeware MATLAB extension Psychtoolbox command bounds=Screen('TextBounds'...) returns a bounding box that is twice as wide as it should be. The Pelli font contains only the characters 0123456789$ plus space and option space. The Pelli font was mostly designed by Denis Pelli. Hörmet Yiltiz designed the $ sign. Hannes Famira tweaked some of the character shapes and converted the PNG files into a standard font file.

The Sloan font file was created by Denis Pelli based on Louise Sloan’s specifications and used for the Pelli-Robson contrast sensitivity chart (Pelli, Robson, & Wilkins, 1988). Louise Sloan’s design has been designated the US standard for acuity testing by the National Academy of Sciences, National Research Council, Committee on Vision (NAS-NRC, 1980). Note that the standard specifies only CDHKNORSVZ, whereas the font file goes beyond that to provide a complete uppercase alphabet A-Z in a consistent style. The C is a Landolt C. The C and O are particularly hard to discriminate from each other, so some studies may wish to omit the C (see Elliott, Whitaker, & Bonette, 1990). This font was developed for the Pelli-Robson Contrast Sensitivity Chart. The font has no descenders and the height and width are equal to the nominal point size requested. Adjoining characters touch.

The Pelli and Sloan fonts are made available here for research purposes and may not be distributed further. Commercial use of these font would require a license from Denis Pelli.


  • Elliott DB, Whitaker D, Bonette L. (1990). Differences in the legibility of letters at contrast threshold using the Pelli-Robson chart. Ophthalmic Physiol Opt. 1990 Oct;10(4):323-6.

  • NAS-NRC (1980). Recommended standard procedures for the clinical measurement and specification of visual acuity. Report of working group 39. Committee on vision. Assembly of Behavioral and Social Sciences, National Research Council, National Academy of Sciences, Washington, D.C. Adv Ophthalmol. 41:103-48.

  • Pelli, D. G., Robson, J. G., & Wilkins, A. J. (1988) The design of a new letter chart for measuring contrast sensitivity. Clinical Vision Sciences 2, 187-199.  

  • Sloan L. (1959). New test charts for the measurement of visual acuity at far and near distances. Am. J. Ophthal. 48, 807-813.