Visual Impairments

So what is a visual impairment?

Last week I wrote about the different types of disability that may impact on how a person accesses information through your website or application. Over the upcoming weeks I’m going to write about each specific disability, their characteristics, range, prevalence and how it impacts their ability to use a computer.


What are the characteristics of a visual impairment?

There are many technical aspects regarding how a visual impairment is classified. Simply put it is the inability to “read and detect fine details or objects at a distance”.

The two broad categories are blindness (including legal blindness for government and welfare purposes) and low vision.

People with blindness perceive little very little to no light. As a result the person relies on using their other senses, such as hearing, to perform every day tasks.

Someone with low vision perceives light fine but has significant trouble making out detail or objects. In some cases this can be corrected with glasses, contacts or surgery.

If someone with low vision currently has it corrected, say through glasses or surgery (like myself), the person no longer has a visual impairment and are categorised as having functional vision.

Colour blindness can also be included as a visual impairment, although is not severe enough to be catorgorised as a disability. The most common type is red-green where the person has trouble seeing the difference between red and green. There is also blue-yellow and monochromacy which is seeing no colour at all.

What are the range of visual impairments?

There are a wide range of visual impairments with many different causes. Some are from birth whilst others may come about through disease such as glaucoma or diabetes and may be cured through surgery.

Colour blindness is hereditary on the X chromosome so is passed down and is more common in men. Women are generally carriers, so will not be colour blind but their sons will be.

As a person ages their eyesight in also ages and can become worse over time. This is usually because inside the eye are muscles which focus the lens to see objects that are far away or up close. Over time, or without enough exercise, say from looking away from the screen often enough, the muscle degraded like any other muscle and their eyesight worsens.


What is the prevalence of visual impairments?

Last week I quoted the estimate of the population of Australia with visual impairments to be between 1 and 2% (from Vision Australia). This included people with blindness and low vision.

However in practical terms there could be a lot more. Some studies show that when people self report a visual impairment tends to be lower than when they are examined by an Optometrist. This could be that some people don’t want to admit they are having trouble seeing. I have seen quite a few people for example reading the paper at arms length loudly proclaiming that they can still see fine.

This also does not include people with colour blindness, which is estimated at around 10% of the male population.


How does this impact their computer use?

For a person who is blind they can use screen or braille readers to read out what is on the screen, using the keyboard (touch typing) to issue commands and move the focus around. Some, while legally blind, may still be able to see a little so may have the screen on but under high contrast conditions to assist with their use.

People with low vision may also choose to have high colour contrast settings to help them read the content. They may also increase the font size by zooming in the screen until they can see.

Someone with colour blindness will likely be able to view all sites fine, until there is dreaded red text on a green background or instructions that are to push the green button not the red button. Thankfully this is a lot less common though still not unheard of (though some train stations in Melbourne still rely on this).

There are many ways to improve your site so people with visual impairments can access information quickly and easily. I will be going through these techniques in detail in future posts.

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