How to tailor your site for people with poor vision


Configurability is king for the low-vision user, so when designing your application or website strive to ensure that pretty much every aspect of content presentation is user-configurable. That means letting the user make text bigger or smaller, change the colour of that text along with the background colour it sits upon, and making the overall layout (in the case of a web page) relative rather than absolute, so it can be widened or narrowed without excessive horizontal scrolling.

Complying with the DDA

Since May 2002, the Disability Discrimination Act has required all service providers take “reasonable steps” to change a practice that makes it “unreasonably difficult” for disabled people to make use of its services. That includes people with visual impairments, and probably means that many websites and software applications have been in breach of the law ever since.

Quite apart from the legal requirements, or the moral satisfaction of doing the right thing, there’s a commercial reality to consider: by alienating low-vision users you’re losing business, be it in terms of eyes on pages or software licences sold. When Tesco launched an access-friendly version of its shopping site a decade ago, it secured £13 million of new business in a year. It’s since gone on to roll the accessibility options into the main website, with a low-vision option that simplifies layout and disables JavaScript, for example.

We’re not talking about technical accessibility, but real-world usability for people with low vision. This is about giving users the choice to experience your content in the way that’s best for them. It isn’t about exchanging your visual design concept for a boring, text-only step back into the 1990s.

Web designers can adopt a simple rule of thumb: make sure the site is readable and usable (these aren’t necessarily the same thing), both when text is enlarged and pages are zoomed (once again, these aren’t necessarily the same thing). By ensuring that non-text content scales properly, employing relative font sizing, and testing it to ensure the layout doesn’t break when the user increases the font, you should have a website that’s accessible to all.

Columns can be problematic for low-vision users who are magnifying the screen and losing the visual context of the website design. Usability studies have shown that users employing screen magnification software often fail to move far enough to the right of the screen to encounter columns of text located in that area. A single-column layout is certainly preferable under such circumstances, but many developers will feel uneasy about what appears to be a retrograde step in terms of web design. The solution is as simple as it is obvious: use stylesheets to provide a low-vision-friendly, single-column option at the click of a button on the homepage.

All developers should carefully consider how text is presented. A number of low-vision usability tests have shown that sans serif type is easier to read than serif. The good news is that research reveals the same is true for people with normal vision, so opting for a sans serif font is a no-brainer. Just because users with low vision will most likely be employing a screen magnifier, doesn’t mean you can’t make things easier for them by ensuring larger font sizes are available before they apply that magnification. Enlargement using a tool of some kind comes at a cost in terms of performance and quality, both of which can be minimised if that larger font is available to begin with.

Legible text resizing should also apply to going smaller as well as bigger, by which I mean that some low-vision conditions, such as those causing tunnel vision, may require users to fit as much text as possible onscreen to be able to see it. When considering the configurability of text, don’t forget to include menus and tables as well as information dialogs and prompts. Finally, never present your text as an image, for so many reasons: high magnification renders it illegible due to pixellation; browser zooming has no effect on text presented this way; colour and contrast settings can’t be customised, and so on.

Configurability touches on many more aspects of usable design than straightforward text and colour issues. Make all timed events adjustable by the user, since those with low vision will take longer to read, and therefore react to, information that’s only briefly displayed onscreen. If you’re using a CAPTCHA system for user authentication, then bear in mind the additional problems these can cause low-vision users. Even people with good eyesight have been known to have difficulty distinguishing the text from the background patterns, so make sure you provide an audio alternative such as reCAPTCHA for low-vision users, or implement a different verification process.

Neither should you ignore audio prompts. A limited field of view, either caused by the visual condition itself or as a result of magnification levels, can mean that it’s very easy to lose context, because there’s relatively little information visible at any one time. Audio cues alongside visual prompts regarding state changes, or the availability of new information, go a long way to solving this problem, and give control back to the low-vision user. Talking of limited fields of view, the relatively small effective screen size being employed by a user of screen-magnification software means that you should thoroughly test your application or site to ensure there are no problems with usability caused by layout issues when the window is zoomed in this fashion.

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