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Adapting accessible charts: Math problems and low vision

Tools and strategies for adapting accessible charts in large print and visual formats.

When it comes to working with charts and visual representations of data, students with low vision may find it challenging to locate and interpret information, as well as explain why it is significant or important. When I was first introduced to charts as a student, I found them to be blurry, hard to understand at times, and difficult to enlarge or present in a format that I could see without straining my eyes. Over the years, I have learned to use several tools and strategies for adapting accessible charts and making charts easier to see with low vision, and began to appreciate charts as a great way to organize information and engage in digital storytelling, many of which I learned during my coursework for Computational and Data Sciences and have since applied to showing students and their teachers how awesome accessible charts can be. Here are my tips for adapting accessible charts for low vision and large print formats, part of my Math Problems for Low Vision series that covers topics related to math accessibility.

Why are charts in math and science hard to see?

Charts provide a way to organize and represent data using symbols, such as bars in a bar chart, points on a scatterplot, lines in a line chart, bins in a histogram, slices in a pie chart, or other visualizations. These visuals or symbols can be difficult for students to interpret or visualize due to several factors, such as:

Even though I found it difficult to view charts when I was in elementary, middle, and high school, learning what goes into adapting charts for low vision and making accessible charts helped me to better advocate for myself and my vision needs, and configure charts in a format that I can see. Learning to explain my usable vision and what I can and can’t see, as well as figuring out what formats and visuals work for me helped me to get so excited about charts that I graduated with a degree that is all about creating, organizing, and analyzing them (an over-simplified description of my Computational and Data Sciences major!).

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Benefits of using digital charts for students with low vision

Whenever possible, I strongly recommend making charts available in a digital format for students with low vision, because this provides more options for using assistive technology to interpret information compared to paper-based charts, and more flexibility with font sizes and display scaling since users don’t have to worry about running out of space on a page. Some examples of assistive technology and accessibility tools that students can use with digital charts include:

Two software options that are available with free options and don’t require coding include Desmos and the Microsoft Office suite, which includes Word, Excel and PowerPoint. Desmos offers several accessibility features along with a sonification feature known as “audio tracing”, and Microsoft provides numerous options for customizing chart visuals and adding alt text/image descriptions to content.

Google Sheets can also be used to create accessible charts, though Google Slides charts do not work well with assistive technology in my experience due to how tables are formatted. Canva is another free program that offers several options for customizing charts and exporting content as a graphic, though users will need to add alt text or image descriptions so that they can be recognized by screen readers.

Quick disclaimer

I was an intern at Microsoft in 2019 on the Excel team, where I worked on a non-accessibility related project. I’ve also held certifications related to Google products including Google Certified Educator Level 2 and the now-retired GSuite certification. All opinions are my own and do not reflect any current or past employer or other organization.

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Creating accessible physical or tactile charts

While digital charts are great, there are still options for printing charts in accessible formats or incorporating tactile components. This can include strategies such as:

I share several visual characteristics to keep in mind when creating accessible charts for low vision audiences throughout this post, though I do not personally use braille due to limited sensitivity in my hands.

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Ensure labels are in large print sizes

When enlarging charts or graphics, sometimes things like axis labels or other text labels would not be enlarged adequately and I wouldn’t be able to see them, and a magnifying glass wouldn’t provide enough magnification for me to read it without straining my eyes. Sometimes, my teachers would either rewrite labels themselves or read labels to me so I could rewrite them in a larger size, or one of us would use text boxes to write over the labels on an image of a chart in a larger size.

Another option I used with a student was having a list of content on the X axis and Y axis printed as a large print bulleted list. I wrote out each of the X axis and Y axis labels in the order that they appeared on the chart, moving from left to right on the X axis and bottom to top on the Y axis. Since the student could see the symbols on the chart and where they aligned, but not the text on the axis, this strategy worked for them.

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Increase line thickness or symbol sizes

Thin lines that are stacked closely together can be challenging for students with low vision to view, especially if they are on a patterned background that also features thin lines. Increasing the line thickness by drawing over a line with marker or adjusting the line thickness in a chart creation program can help students identify lines more easily. When adjusting the line thickness in a drawing or chart creation tool, I recommend increasing the gap width to provide more spacing between symbols.

When I’m working with scatterplots or dot plots, it’s helpful to increase the size of symbols so that they are easier to locate or identify. On particularly information-dense charts or situations where dots are close together, increasing the opacity may be more helpful with locating dots or rescaling the chart to accommodate increased spacing between dots may be a better option.

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Print charts in full color whenever possible

I rely a lot on color as a way of labeling and conveying information, and find it helpful when data in a chart is color-coded so I can locate it more easily. As a young student with low vision, I would find it helpful when the different bars in a bar chart were different colors, or dots in a scatterplot had different colors for different categories, and this valuable information would be lost when graphics were printed in a black and white or grayscale format. Sometimes, I would color in bar charts or add color in other places so that I could see information more clearly without having to constantly rely on text labels, small shapes, or other visual differences that are harder to pick up on. I personally prefer bright, saturated colors, and would often organize things in “rainbow order” based on the color spectrum, with red being the highest values and purple or another darker color being the lowest values.

That said, some students experience color deficiencies or colorblindness, and it is important not to use color as the sole means of conveying information. Things like text labels for an axis or key, different shapes to represent symbols or categories (such as triangles, squares, circles, etc), patterns or textures, and similar labeling tools can be used along with color to convey information about data.

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Add alt text and image descriptions to increase comprehension

One of the most helpful tools for accessing charts for students with low vision is access to alt text and image descriptions, which provide a text-based description of essential visual content. Alt text is embedded into an image so it can be read out loud by a screen reader, while image descriptions are “exposed” as a caption and can be read out loud by a screen reader or enlarged visually. While I can still use my vision to look at charts, tools like image descriptions help fill in blanks on things that I might not otherwise pick up on, or confirm that I am looking at something correctly.

For younger students or less complex charts with fewer data points, alt text and image descriptions may be more detailed and mention every single symbol or item in a chart, while more complex charts may focus on the “highlights” such as summary statistics. However, the following information should always be included when writing descriptions of charts for students with low vision:

While it is good practice to highlight points of interest in a chart, such as which value is the largest or interesting patterns or groups, in this context I am assuming that the student is expected to identify these patterns on their own with the information presented, which would be different than charts presented on a website, in an article, etc.

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Other tips for adapting accessible charts for low vision students

By Veronica Lewis/Veronica With Four Eyes, www.veroniiiica.com 

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