Proceedings of: Workshop on Improving Building Design for Persons with Low Vision

Operational Definitions

So if your vision is low, you have low vision acuity. So low vision is kind of a shorthand notation for low visual acuity. However, the use of the term “low vision” has gone well beyond just talking about visual acuity. In fact, it refers to any chronic visual impairments that cause functional limitations or disability (slide 3).

We say it’s chronic – by definition, it can’t be corrected with medical or surgical interventions. If you can take out the cataract, we don’t call it low vision; if we can give you glasses, we don’t call it low vision. We correct that. So low vision is after everything has been done that can be done and you’re still left with a bit of impairment that interferes with daily activities.

Visual impairment can refer to loss of visual acuity – I’ll explain what that is; loss of contrast sensitivity – I’ll explain what that is; loss of peripheral vision; blind spots and a number of other types of visual bursts, color vision deficiencies and so on, which – and usually, visual impairment is defined in terms of some type of clinical test that gives us a score that we can compare to norms and say whether or not there’s an impairment there. Some impairments cause more problems with daily functioning than other types of impairments and we’ll emphasize those that are most –have the biggest effect on daily functioning.

Functional limitations is a term that refers to an increased difficulty in being able to do certain functions that require vision. Reading is one of the functions we single out; mobility; visual motor activities – this is eye-hand coordination type things, using your hands under visual control; and interpreting visual information. You know, if you’re watching a reality TV show, in order to know what’s going on, you have to be able to interpret what you’re seeing. So an awful lot of what we do every day involves visual information processing and interpreting visual information.

So functional limitations usually imply that you have an increased difficulty doing it, but it’s not impossible to do. Whereas disability usually refers to the activities themselves that are impacted. So if you’re unable to perform your usual customary activities because of your visual impairment, we say you’re suffering a disability. And especially with the new [term] –– International Classification Function, disability has come to be defined strictly in terms of activities. So the two more or less go hand in hand, but you’re not necessarily disabled if you have a functional limitation.