Herman Snellen was a Dutch ophthalmologist born in 1834, best known for developing the Snellen chart, a tool used to measure visual acuity. His chart features letters of varying sizes, allowing eye care professionals to assess how well a person can see at different distances. Snellen's work significantly advanced the field of optometry and eye care. The Snellen chart remains a standard method for vision testing worldwide, helping to identify vision problems and ensuring that individuals receive appropriate corrective measures, such as glasses or contact lenses.