Letters in Sight: Optimizing typography for people with low vision

Reading is one of the most demanded tasks by people with low vision and a difficulty in this task can have a major impact on the development of the person in society. 

Accessibility to printed or digital texts is not only a pressing need, but also a right of people with low vision. 

If we want to improve people’s access to reading, we must understand that when we talk about reading ability, we cannot limit ourselves to visual function.

Let’s imagine Maria, a person with low vision due to age-related macular degeneration, passionate about reading, although glasses and optical aids are her allies, Maria often encounters texts that seem to challenge her reading. How is it possible that, making use of the best prescribed aids, some texts remain inaccessible?

This is because the dilemma goes beyond a proper prescription of glasses and optical aids. Maria’s vision is unique, built from her own experiences and preferences and we need to know: How does she use her vision? What are the environmental cues that may affect her reading? What are the characteristics of those texts she usually reads? What does she want to read?

And of course, there are personal visual skills that must be taken into account, but we will address that in another publication.

Next, we would like to offer some suggestions on how to optimize the presentation of texts to people with low vision, since it is not enough to recommend a font type, but the characteristics of that font must be considered.

If you are interested in the complete document, you can find the downloadable PDF at the end.

Typographical parameters

The author Arditi (2010) established some typographic parameters to be considered in order to select an appropriate font size and typeface. Some of these parameters are point size, letter height, stroke width, letter spacing, serif size, line spacing and letter drop.

Font type

There is a great diversity of typographies, some of them with designs that could affect legibility. It is recommended that fonts be sans serif, although some people have difficulty differentiating, for example, between a letter o and a letter c, so a small serif at the ends of the letter c might give them a visual clue to differentiate one letter from another. Recommended fonts for people with low vision are Verdana, Arial, Century Gothic, Tahoma, Courier, Tiresias and Atkinson Hyperlegible.

Let’s look at the following examples. Can you see that there is a noticeable difference in legibility?

Let’s look at one more example, the following figure used in a study shows the same text in six different fonts, with a size of 18 points, placed at 40 cm distance. Four levels of visual acuity are simulated. We can see how some fonts favor that they can be perceived by our eyes.

Letter size

Some studies show that font size influences reading speed or the number of words per minute a person can read. The size varies for each person, but some recommendations are: 

  • In digital material, the recommended sizes are between 14 and 16 points.
  • The ratio between the height and width of the letter is recommended to be 3 to 2.
  • Avoid the use of bold type, use it only in a maximum of two words in a paragraph to highlight important information. 
  • Not all people with low vision need magnification.
  • Avoid the use of sustained capital letters throughout the text, even though in some studies sustained capital letters have been favorable in people with very low visual acuity, it is said that when the text is written entirely in capital letters, between 10% and 20% of the reading performance can be lost. 
  • Some people with low vision are guided by the shape of words, so sustained capitalization is not always the best choice. Let’s see an example:

Spacing between letters

Sometimes when reading there may be a crowding effect, to avoid this, the spacing between stimuli can be modified, in this case, the spacing between letters. The recommended spacing will depend on the field of vision of each person, but it is recommended to leave at least a space of ¼ of the size of the letter. Here are some examples with different spacing and font types:

Alignment 

It is suggested to always use the left alignment.

Line spacing

Sometimes people with low vision have difficulty finding the next line and in order to avoid the crowding effect a spacing of 1.5 to 2 or a spacing between 25% to 30% of the font size in points is recommended. In addition, it is important to maintain spacing between paragraphs. The following figure shows an example of inadequate spacing at the top and an example of adequate spacing of 1.5 at the bottom.

Line lengths

Lines or lines of great length imply a greater amount of eye movements, which are usually altered in people with low vision. Lines containing between 70-90 characters are recommended.

Page layout

The distribution or design of the page should be simple and homogeneous, avoiding photos or images within the text.

Some people need to use screen readers to access digital documents, so it is recommended to adequately label titles, subtitles or headings using the styles offered in the text editing program used.

Contrast

Usually, people with low vision have low contrast sensitivity, so it is important to take this into account when preparing a text. Some commonly used contrasts are:

  • White background with black lettering
  • Yellow background with black lettering
  • Black background with white lettering
  • Black background with yellow lettering
  • Blue background with white or light blue lettering

Let’s consider some examples, the first row shows good examples of high contrast, and the second row shows an inadequate use of contrast.

Let’s consider one more example, using grayscale.

It is important that there is at least 80% contrast between the two colors, to check this you can use programs such as:

https://webaim.org/resources/contrastchecker/

Images

The images of the texts should have high contrast, with simple, thick strokes and with visual closure if necessary. It is suggested not to intersperse images within a text.

Printing text

If the material is presented in printed form, it is important that the paper is unglossed, sepia tone paper or light blue or yellow colors are recommended. In some cases people use a yellow acetate to diminish the white tone of the paper, but increase the contrast.

Printing on one side only is recommended.

Technology for reading improvement

There is growing evidence of the benefits of electronic devices for people with low vision, especially for reading. 

When using electronic devices such as computers, tablets or cell phones, it is advisable to take into account the dimensions of the device.

In addition, it is recommended to use the available accessibility features to adapt the display and text presentation. This involves activating options such as contrast, brightness modification, font size adjustment, as well as magnifier or screen reader functions if necessary.

Some people with low vision benefit from scrolling text in front of their eyes instead of moving their eyes. For this reason, mobile applications such as Eccentric Visor, which facilitate the visualization by scrolling text, are recommended. This application also allows other modifications to be made to the font type, font size and contrast of the screen. For more information, please visit the Solutions section of our website.

Aspects to be considered

The above recommendations are based primarily on results obtained from various studies. However, visual functioning may differ considerably from person to person, even in cases with the same diagnosis and similar visual acuity levels. 

Therefore, it is essential to perform a functional vision assessment, which is individualized and carried out by a professional in the field. 

We encourage you to share this information. If you have any suggestions, require more information, or need contact with a professional, please write to us at contact@tiflolabs.com

If you are interested in downloading this information in PDF format you can do so by clicking on the following button:

References

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