Clear Print: Executive Summary
An evidence-based review of the research on typeface legibility for
readers with low vision.
June 2006
Lead author:
Elizabeth Russell-Minda, M.A., VREBR Project Coordinator
Co-authors:
Jeffrey Jutai. Ph.D., C.Psych., VREBR Project Director
Graham Strong, O.D., M.Sc., VREBR Investigator
Collaborators:
Kent Campbell, Ph.D., Bloorview KidsRehab
Deborah Gold, Ph.D., CNIB
Julia Morgan, CNIB
Lisa Pretty, CNIB
Lesley Wilmot, CNIB
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April 2006
This report is a collaborative effort of the VREBR Project Team and CNIB
Research.
Copyright Statement
This document is considered the property of the VREBR Project Team and CNIB
Research. No part of this document shall be copied, quoted or distributed
without permission from the authors. Electronic distribution or saving to
another file type (such as .rtf or .html, for example) is also prohibited.
Contact Information
Please address correspondence about this document to:
Dr. Jeffrey Jutai, National Director of Research, CNIB
University of Western Ontario,
Dept. of Physical Medicine & Rehabilitation
Parkwood Hospital Site
Hobbins Building, Suite H-403
801 Commissioners Rd. East
London, ON N6C 5J1
(519) 685-4292 x42626
E-mail: jjutai@uwo.ca
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Contents
Objectives of the Report
4
Methodology
4
International Guidelines and Standards
4
Reading and Low Vision
5
Eye Conditions that Affect Reading Ability
5
Age-Related Macular Degeneration
5
Cataract
6
Glaucoma
6
Diabetic Retinopathy
6
Overview of Font Characteristics
6
Spacing
6
Letter Height (x-height and t-height)
6
Serifs
7
Sans-Serifs
7
Stroke Width
8
Variables that Affect Text Legibility and Readability
8
Contrast
8
Type Colour
8
Heaviness
8
Point Size
8
Leading (Spacing between lines of text)
9
Letter Spacing
9
Font Family and Style
9
Other Considerations
10
Medical Labeling
10
Conclusions
11
References
12
Appendix I—Studies and Publications Selected for Review
14
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Clear Print: Executive Summary
Readability shouldn’t be an afterthought when producing written materials. It
should be the first step in making information accessible to anyone. With this
hypothesis in mind, the VREBR Project Team and CNIB Research set out to
identify general guidelines for producing accessible print materials. This
document summarizes the resulting Clear Print report, published April 2006.
Objectives of the Report
The objectives of the Clear Print report were to:
 review existing research about the legibility and readability of typefaces
 locate any Canadian or international standards or guidelines related to
typeface design and legibility
 address any French language typeface characteristics (accent marks, for
example) as they affect low vision readers of print copy
Although it was not the primary goal of the study, literature related to the
legibility of medication labelling was also considered.
Methodology
The Clear Print study assessed existing research using evidence-based models
and methods in order to develop conclusions and make recommendations.
Research studies were located using multiple online databases, grey literature
sources, and general Web searches.
The search criteria included: controlled or uncontrolled; experimental or nonexperimental; randomized or non-randomized; and published or unpublished
research. The criteria for “low vision condition” included any eye condition
where reading printed copy causes some amount of difficulty. Literature
devoted to factors associated with online font or computer accessibility was
excluded from the review.
For a list of studies and grey literature sources selected for this review, see
Studies and Publications Selected for Review—Appendix I. All of the studies
selected for review (17 total) contain research on some form of font legibility in
relation to low vision reading. A good majority of the studies included subjects
with normal vision and sample sizes were usually small.
International Guidelines and Standards
During the search for international font legibility standards or guidelines for low
vision readers, the Clear Print study did not locate any definitive international
standards or guidelines on font size and type for reading with low vision.
Perhaps the closest example of a “standard” in this regard, is a document
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published by the International Council of Ophthalmology, entitled Visual
Standards: Aspects and Ranges of Vision Loss,1 which contains information and
a chart on the ranges of visual acuity and reading ability.
The study did find that most international library councils, printing houses and
foundations for the blind and visually impaired (Canada, US, UK, and
Australia), have guidelines and standards for large print materials. (See
Appendix II for a detailed listing of these organizations). In general, there was
agreement between these organizations on standards for printed material in
terms of acceptable font size and other text characteristics that increase
legibility and accessibility.
In the search for medication labelling and typeface legibility standards in
Canada and the United States, we located several sources outlining rules and
regulations concerning standardized formats for health-related information and
medication (non-prescription or over-the-counter—OTC) labelling.
Reading and Low Vision
Reading is critical to full participation in modern society. For the many
individuals with vision loss, reading presents a major challenge. Low vision can
be defined as the inability to read the newspaper or recognize faces, even
using corrective lenses, at a normal reading distance of 40 cm.2 Many older
people have difficulty reading standard text, including medical information,
hospital forms, and medication labels. Some people who can read standard
print may find it tiring and prefer to read large print whenever they can.
Successful rehabilitation primarily involves enhancement of whatever usable
vision remains.3 The most direct method for enhancing vision is magnification,
usually consisting of relatively portable and inexpensive hand-held or stand
magnifiers, or electronic devices such as CCTVs and other devices.
Environmental modifications such as proper illumination and viewing distance
are also important variables.
Due to problems associated with high levels of magnification, such as reduction
in the size of the usable field, making print more legible or readable can reduce
or eliminate the need for magnification.3
Eye Conditions that Affect Reading Ability
In terms of causing difficulties when reading print, the following low vision
conditions are among the most prevalent.
Age-Related Macular Degeneration
AMD is the leading cause of visual impairment in the developed world. It is also
the most common cause of losing the ability to read print, since it affects
central vision, which is used for seeing detail. Since AMD progressively affects
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the central vision, people with AMD must use peripheral vision to read, which
has been shown to be a slow and inefficient process.2-7
Cataract
Cataract is another common age-related condition where the lens of the eye
becomes cloudy or opaque. If vision is blurred by cataracts, reading
performance will be degraded.8 With severe cataract, people can see light and
detect colour contrast, but usually cannot read print. When people with
cataracts receive laser treatment, they can usually begin to read large print
again. Reading materials with good contrast can help people with cataracts.
Glaucoma
Since glaucoma is considered a “tunnel vision” condition, central vision is
usually unaffected, allowing the person to continue to read print. However,
peripheral vision is usually affected. As people with glaucoma age, they usually
require progressively larger print materials.
Diabetic Retinopathy
Diabetic retinopathy (DR) is a major cause of vision loss for working-age
adults. DR can lead to patchy vision resulting in orientation difficulties. Some
people with patchy vision have a fairly even sight loss across the visual field
and may require print materials with good contrast and large print. Some
individuals may lose peripheral sight first, and can continue to read standard
sized text for longer periods.
Overview of Font Characteristics
Spacing
The two main types of spacing are fixed-width and proportional. In fixed-width
fonts (such as Courier New), each character takes up the same amount of
horizontal space. In a proportionally-spaced font (such as Times or Arial),
different letters take up different amounts of horizontal space.9
Fixed-width font (Courier New)
Proportionally-spaced font (Times New Roman)
Proportionally-spaced fonts can pack more characters into a line of text than
fixed width fonts, and are thus preferred by typographers.
Letter Height (x-height and t-height)
The x-height is defined as the height of the letter “x” in any given font, and is
the specific height of the lower case letters. The “t-height” is defined as the
height to the bottom of the crossbar of the letter “t” in any given font (lower
case). Refer to Figure 2 below. Depending on the font, t- and x-height may be
different or the same.
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Figure 1 Example of t-height and x-height (100 pt. APHont not shown
to scale)†
Serifs
Serifs are the fine lines that extend horizontally from the main strokes of a
letter.10 Examples of serif fonts include: Times, Palatino, Garamond, Century
Schoolbook, and Book Antiqua. Serif fonts are frequently used in newspapers
and books where the space for print is tight.
The quick brown fox (Times)
The quick brown fox (Palatino)
The quick brown fox (Book Antiqua)
Sans-Serifs
Sans-serif fonts are those fonts which have letters with straight lines and no
curls or appendixes. Examples of sans-serif fonts include: Arial, Helvetica,
Tahoma, Avant-Garde, Univers, Century Gothic, Verdana, and all other fonts
characterized by clean letterforms.
The quick brown fox (Arial)
The quick brown fox (Tahoma)
The quick brown fox (Century Gothic)
Figure 2 Examples of serifs and sans serifs.‡
†
Kitchel EJ. Large Print: Guidelines for Optimal Readability and APHont a font for low vision. Retrieved March 27, 2006 from
http://www.aph.org/edresearch/lpguide.htm.
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Stroke Width
Stroke width refers to the width of each stroke in a letter. A font may have a
uniform stroke width in which the stroke is the same width throughout each
letter, for example the font Arial. Or, a font may have a varying stroke width in
which some portions of the stroke are thinner than others, as seen in the font
Times New Roman. Fonts may also be “heavy” (have a generally wide stroke
width), referred to as “bold,” or a thin stroke width, referred to as “light.”
Variables that Affect Text Legibility and Readability
Contrast
Many individuals with low vision have difficulty with objects that are poorly
contrasted with their surroundings.11 People with central vision loss, who use
peripheral vision for reading, are especially affected by issues related to
contrast. General guidelines recommend that text should be printed with the
highest possible amount of contrast. There is also good evidence that for many
low vision readers (older or partially-sighted) that light (white or yellow) letters
on a dark (black) background are even more readable than dark letters on a
light background.
Type Colour
The choice of text colour can affect low vision readers. Partial sight, aging and
congenital colour deficits (“colour blindness”) all produce changes in perception
that reduce the effectiveness of certain colour combinations. Two colours that
contrast sharply to someone with normal vision may be far less distinguishable
to someone with a visual disorder.12 It is difficult to achieve high contrast with
colour combinations other than black and white. Colour combinations that
provide the maximum contrast, such as black on white, and black on yellow
give the best legibility results.13 It is generally recommended that coloured text
be used mainly for larger or highlighted text, such as headlines and titles.14
Heaviness
The heaviness of a font can have an effect on legibility. It is generally
recommended that medium heaviness be used and light type should be
avoided. Bold fonts are preferable for emphasis, rather than italics or allcapitals. 15 Some studies have shown relationships between font heaviness and
specific low vision conditions. Bold fonts have been shown to be more useful
for people with glaucoma or cataract. Stroke thickness is especially important
for low vision readers because thinly stroked letters result in poor contrast.
Point Size
A major problem with point size is that different fonts with the same point size
will have different heights and widths.16, 17 The most accepted guideline for low
‡
See: http://www.symplebyte.com/general_usage/fonts/serif_or_sans-serif.html
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vision reading materials is that type should be large, preferable at least 16 to
18 points. The relationship between readability and point size differs somewhat
among typefaces and this should be taken into consideration when developing
print materials. For normally sighted readers, point size should range between
9 and 14.
Leading (Spacing between lines of text)
Leading, or spacing between lines of text, should be at least 25 to 30 per cent
of the point size. This is because many people with partial sight have difficulty
finding the beginning of the next line while reading.14 Some research points to
optimal leading ranges of 1 to 4 points, with heavier typefaces requiring more
leading.15 Others have suggested that four point leading should be used when
preparing materials for low vision readers.
Figure 3 Examples of leading§
Letter Spacing
Closely packed small letters are much harder to read compared to the same
letters which are not closely packed.18 Reduced letter legibility has been
termed the “crowding effect.”19 Individuals with compromised macular
functions often have reduced reading performance when letter “crowding” is
present.20 At least one study suggests that where possible, spacing should be
wide, and fixed-width fonts, rather than proportionally spaced fonts should be
used for individuals with low vision.14
Font Family and Style
While there is little reliable information on the comparative legibility of
typefaces, there is some evidence that a Roman typeface, using upper and
lower cases, is more readable than italics, oblique, or condensed text. In
general, there is disagreement in the research as to which font is the most
§
Arditi A. Making Text Legible: Designing for People with Partial Sight. Lighthouse International 2000. See:
http://www.lighthouse.org/print_leg.htm
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legible for low vision readers. Standard serif and sans serif fonts (such as Arial
or Times Roman) are generally considered to be the best fonts for legibility.
There is some evidence that sans serif fonts are more legible when character
size is small relative to the reader’s visual ability.14
Other Considerations
Other considerations include margin space, paper finish, and distinctiveness.
Extra-wide binding margins are helpful in bound material because it makes it
easier to hold the volume flat, and many low vision aids, such as stand and
video magnifiers, are easiest to use on a flat surface. Spiral binding can be
helpful as well.
Paper finish or texture can have an impact on low vision reading. Glossy
surfaces can produce additional glare. Opaque or matte finish paper is
recommended.
In addition, publications that look similar in design and layout can cause
confusion regarding the ability to distinguish one publication from another. The
use of distinctive colours, sizes and formats on the covers can be especially
helpful to older individuals and those who are visually impaired.14
Medical Labeling
The U.S. Department of Health and Human Services, Food and Drug
Administration report on over-the-counter (OTC) labelling requirements21
contains recommendations for medication labelling, and although these are
guidelines for the general population, they could certainly be extrapolated to
individuals with low vision. Based on consumer feedback, the report suggests
using at least a 6-point type size for all OTC labelling and recommends the font
style be “any clear, easy-to-read type style,” suggesting the use of Helvetica or
Univers (sans serif fonts). With respect to the contrast of the labels and drug
fact sheets, the agency recommends that type be “all black or one dark color,
printed on a white or other light, neutral color, contrasting background.”
A Canadian Public Health Association publication entitled, “Good Medicine for
Seniors: Guidelines for Plain Language and Good Design in Prescription
Medication”22 outlines suggestions for legible and clear design for medication
labelling. These guidelines are based in part on a technical report published by
the Nonprescription Drug Manufacturers Association of Canada.23 Both
recommend the use of sans serif fonts for packaging (Helvetica, Arial, and
Univers, for example) if the type size is smaller than 10 points. Other
suggestions include the appropriate use of white space, leading, type
alignment, line length, contrast, and emphasis. Their recommendation
regarding contrast is in line with almost all other guidelines on contrast: dark
lettering on a light surface; brightness and high contrast help readability and
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glossy or reflecting surfaces do not. When the type is small, leading should be
adjusted so that the space between lines increases by about two points.
Conclusions
The Clear Print report concludes that typeface legibility for readers with low
vision is a verifiable and important consideration when developing printed
materials. However, the report also found several studies where the ultimate
outcome for subjects regarding choice of font (both style and size) was based
primarily on personal preference. Interestingly, custom designed fonts for large
print materials, such as Tiresias, were preferred by individuals with low vision
over standard fonts such as Times Roman or Arial.
With respect to international standards and guidelines on typeface legibility
and design, the best evidence was to be found with individual low vision and
blindness organizations, national library services’ recommendations, and other
grey sources. The study’s search for French language considerations, such as
accent marks and low vision reading, produced little research to date.
The Clear Print study does highlight the fact that multiple variables can affect
the reading performance of individuals with low vision. Certainly, the size and
type of fonts used in large print materials are some of the most important
considerations; however, it is clear that other factors play a role in determining
the best conditions for legibility. The presence or absence of serifs, contrast of
text to page, thickness of letters, interletter spacing, leading, and the medium
on which text is printed (medication labels for example), can all affect the
legibility of type.
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References
1
Colenbrander A. Visual Standards—Aspects and Ranges of Vision Loss. Report
prepared for the International council of Ophthalmology at the 29th International Congress
of Ophthalmology. 2002. Sydney, Australia.
2
Chung S, Mansfield JS, and Legge GE. Psychophysics of reading. XVIII. The effect of
print size on reading speed in normal peripheral vision. Vision Research 1998;38:29492962.
3
Arditi A. Adjustable typography: an approach to enhancing low vision text accessibility.
Ergonomics 2004;47(5):469-482.
4
Faye EE, Clinical Low Vision, 2nd. Ed. Boston, MA: Little, Brown, & Co., 1984.
5
Legge GE, Rubin GS, Pelli DG, Schleske MM. Psychophysics of reading-I. Normal
vision. Vis Res 1985;25:253-66.
6
Rubin GS. Predicting reading performance in low vision observers with age-related
maculopathy (ARM). In: Woo GC, editor. Low Vision: Principles and Applications. New
York:Springer-Verlag, 1986:323-33.
7
Lovie-Kitchin JE, Woo GC. Effect of magnification and field of view on reading speed
using a CCTV. In: Woo GC, editor. Low Vision: Principles and Applications. New
York:Springer-Verlag, 1986:308-22.
8
Rumney NJ. Using visual thresholds to establish low vision performance. Ophthalmic
Physiol Opt 1995;15(Suppl 1):S18-24.
9
Mansfield J, Legge G, and Bane M. Psychophysics of reading XV: Font effects in normal
and low vision reading. Invest Ophthalmol Vis Sci 1996;37:1492-1501.
10
Lannon JM (Ed.). Chapter 15: Designing pages and documents. Technical
Communication (8th ed). pp.304-22. New York: Addison Wesley Longman, Inc. 2000.
11
Rubin GS and Legge GE. Psychophysics of Reading-VI. The role of contrast in low
vision. Vis Res 1988;29(1):79-91.
12
Arditi A. Effective Colour Contrast. Lighthouse International. 1999. See
http://www.lighthouse.org/color_contrast.htm
13
Eperjesi F, Fowler CW, Kempster AJ. Luminance and chromatic contrast effects on
reading and object recognition in low vision: a review of the literature. Ophthalmic and
Physiological Optics 1995;15(6):561-568.
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14
Arditi A. Making Text Legible: Designing for People with Partial Sight. Lighthouse
International. 2000. See: http://www.lighthouse.org/print_leg.htm
15
Rehe RF. Typography: how to make it most legible. Indiana: Design Research
International. 1974. pp.1-62.
16
Johnston AW. Making sense of the M, N and logMAR system of specifying visual acuity.
Problems in Optom 1991;3:394-107.
17
Oduntan AO. An analysis of print sizes of South African newspapers in relation to
prescription of reading devices for low vision patients S Afr Optom 2005;64(2):64-70.
18
Liu L and Arditi A. Apparent string shortening concomitant with letter crowding. Vis Res
2000;40:1059-1067.
19
Liu L and Arditi A. How crowding affects letter confusion. Optometry and Vision Science
2001;78:50-55.
20
Cummings RW, Whittaker SG, Watson GR, and Budd JM. Scanning characters and
reading with a central scotoma. American Journal of Optometry and Physiological Optics
1985;62(12):833-43.
21
Over-the-Counter Human Drugs; Labeling Requirements. U.S. Department of Health
and Human Services, Food and Drug Administration. Rockville, MD. January 4, 1999. See:
http://www.fda.gov/cder/otc/label/cd9845.pdf
22
Canadian Public Health Association. Good Medicine for Seniors: Guidelines for Plain
Language and Good Design for Seniors. 2002. See:
http://www.nlhp.cpha.ca/Labels/seniors/english/cover.htm
23
Nonprescription Drug Manufacturers Association of Canada. NDMAC Technical
Research Paper for Improving Label Comprehension. 2006. See:
http://www.ndmac.ca/index.cfm?fuseaction=main.DspSubPage&PageID=9&SubPageID=7
56&fkMainPage=9
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Appendix I—Studies and Publications Selected for
Review
1. Arditi A and Cho J. Serifs and font legibility. Vision Research
2005;45:2926-2933.
2. Arditi, A. Adjustable typography: An approach to enhancing low vision
text accessibility. Ergonomics 2004;47(5):469–482.
3. Arditi A, Knoblauch K, & Grunwald I. Reading with fixed and variable
character pitch. Journal of the Optical Society of America 1990;A
(7):2011–2015.
4. Campbell K, et al. CNIB/OCAD typographic legibility research project—
“Clear Print” report. May 2005. CNIB Research.
5. Chung ST. The effect of letter spacing on reading speed in central and
peripheral vision. Invest Ophthalmol Vis Sci 2002; 43(4):1270-1276.
6. Chung STL, Mansfield JS, Legge GE. Psychophysics of reading. XVIII.
The effect of print size on reading speed in normal peripheral vision.
Vision Research 1998; 38(19):2949-2962.
7. Drummond SR, Drummond RS, Dutton GN. Visual acuity and the
ability of the visually impaired to read medication instructions. Br J
Ophthalmol 2004; 88(12):1541-1542.
8. Estey A, Jeremy P, Jones M. Developing printed materials for patients
with visual deficiencies. J Ophthalmic Nurs Technol 1990; 9(6):247249.
9. Liu, L., & Arditi, A. How crowding affects letter confusion. Optometry
and Vision Science 2001; 78:50-55.
10. Liu, L., & Arditi, A. Apparent string shortening concomitant with
letter crowding. Vision Research 2000;40:1059-1067.
11. MacKeben M. Enhancement of peripheral letter recognition by
typographic features. Vis Impair Res 2000;2(2):95-103.
12. Mansfield JS, Legge GE, & Bane MC. Psychophysics of reading Xv:
Font effects in normal and low vision. Investigative Ophthalmology and
Visual Science 1996; 37(8):1492–1501.
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13. Moriarty SE and Scheiner EC. A study of close-set text type. Journal
of Applied Psychology 1984;69:700-702.
14. Morris R, Aquilante K, Yager D & Bigelow C. Serifs slow rsvp reading
at very small sizes, but don’t matter at larger sizes. Society for
Information Display International Symposium Digest of Technical
Papers 2002;33(1):244-247. Retrieved March 31, 2006 from:
http://www.cs.umb.edu/~ram/rsvp/publications/SerifsSubmittedV2.do
c
15. Morris RA, Berry K, Hargreaves KA, Liarokapis D. How typeface
variation and typographic scaling affect readability at small sizes.
Society for Imaging Science and Technology, Portland: Proceedings of
the 7th International Congress on Advances in Non-Impact Printing
Technologies, 1991.
16. Perera S. An investigation into the legibility of large print typefaces.
December 2001. RNIB Scientific Research Unit. Retrieved March 24,
2006 from http://www.tiresias.org/fonts/lpfont/report/index.htm
17.
Yager, D., Aquilante, K., & Plass, R. High and low luminance
letters, acuity reserve,and font effects on reading speed. Vision
Research 1998;38:2527-2531.
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