Visual Acuity is a measure of best possible vision. The chart should be well lit, and the patient should wear glasses if appropriate.
Glasses fall into three types. (excluding non refractive glasses such as sun-glasses)
- Distance Glasses. Worn for watching TV, driving the car, going to the cinema. Patients may not wear their ‘driving’ glasses all the time, but should use them when recording distance vision
- Reading Glasses. These are used for reading, knitting or other close work. They are worn by presbyopes, whose hardened lenses are unable to accomodate adequately for near vision
- Bifocals or Varifocals, combine both distance and reading into one lens, the patient should be instructed to look through the distance part of the lens for distance acuity, and the reading part for near vision.
Wearing distance glasses if they have them. Record vision from 6 meters (if using a 6m Snellen chart, 3m if using a 3m chart)
Record the vision in each eye in turn. If the vision is less than 6/6 and the patient does not have glasses (either because they don’t have them with them, or they have never been prescribed them) then pinhole testing should be undertaken to see if this can improve the vision to 6/6 or better.
Test using a near vision chart, with each eye in turn, using reading glasses if they normally use them.
Here is a PDF snellen chart, which you can print on A4 paper.