(2021-10-09). [Perspectives] Digitising the vision test. thelancet.com The Dutch ophthalmologist Herman Snellen invented his visual chart in 1862 and it has remained the basis for assessing visual acuity since then. The Snellen chart relies on assessing the ability to discriminate high contrast symbols (optotypes) by asking a person to identify rows of letters at a fixed distance, showing them increasingly smaller sizes. Yet quantifying how well an individual can distinguish visual information in a fast and reliable way is a surprisingly difficult task. Despite the ubiquity of chart-based visual acuity assessments, these tests suffer from some shortcomings.