The Snellen visual acuity test is commonly used to measure an individual's visual acuity test is commonly used to measure an individual's visual acuity.
The subsequent experiments of Snellen, Senftleben, and, more lately, of Turner, seem to show that if the eyeball be protected from the impingement of foreign particles, an accident to which it is liable owing to its state of anaesthesia, the ulceration may be warded off indefinitely.
Patients are usually given the Snellen Chart (a chart with rows of large and small letters).