Defining visual impairment

In order to understand the epidemiology of visual impairment we need to use an agreed definition of visual acuity. This will allow us to compare studies from different locations and also measure impact. In this step we look at the World Health Organization’s (WHO) classification of visual impairment, which will be used throughout the course. How can this classification be applied to your own work?

Visual acuity conversion chart

Throughout the course we use the Snellen (metre) measurement of visual acuity. In other contexts Decimal or LogMAR measurement systems are preferred. The chart shown below allows you to convert from one system to another.