He took over directorship of the Netherlands Hospital for Eye Patients (Nederlandsch Gasthuis voor Ooglijders), after Franciscus Donders.

[1] Herman Snellen studied medicine at Utrecht University under Donders, Gerardus Johannes Mulder and Jacobus Schroeder van der Kolk.

He specialized in ophthalmology and worked as an assistant physician at the Netherlands Hospital for Eye Patients after he had completed his degree.

[5] The most significant innovation was Snellen's use of what he called optotypes, specially designed characters generated on a 5x5 grid, rather than using standard fonts.

Since its inception, more copies of the Snellen Chart have been sold in the United States than any other poster.