A history of visual acuity testing and optotypes.

After going into the etymology of the word "optotype", this article covers some tasks in ancient times that required good visual acuity (VA). Around 300 BCE, Euclid formulated the existence of a visual cone with a minimal visual angle at its tip. Trials to test VA appeared AD 1754. Around that time, texts were introduced by opticians in order to be able to prescribe more reliably. In the early nineteenth century, the need for VA tests in ophthalmology resulted in German and English test charts. Numerous variants emerged after the first edition of Snellen's optotypes in 1862 in The Netherlands. However, 100 years later there was still no standard optotype to reliably test VA. Multidisciplinary approaches between ophthalmology, linguistics, psychology and psychophysics improved optotypes and VA testing, which led to the more reliable LogMAR charts. Recent advances in aids and therapies for the blind and severely visually handicapped, necessitate further development of new and standardized VA tests.