Notice: This website was a student project from 2009 and is no longer actively maintained. I’ve left these resources archived, but be warned they may be out of date or no longer relevant.

If you’re looking for more current information from Jessica Mevius, OTR, MOT, you can go to my private practice website — Therapy Squared (


Snellen Chart

Snellen Chart


The Snellen Chart is used to test visual acuity. The client is asked to cover one eye and read the letters out loud, starting at the top of the chart and working his/her way down until one complete row can no longer be read. Each eye is tested separately and then both are tested together. Visual acuity is then expressed as 20/20, or a similar number, meaning the smallest letters accurately read on the chart.36

The original Snellen Chart only has the ten letters C, D, E, F, L, N, O, P, T, Z but there are many different variations available today.

Where to Obtain

Linked PDF:

Attached PDF

Who is originally responsible for this Tool?

Snellen Charts are named after the Dutch ophthalmologist Herman Snellen. He developed the chart in 1862.

Assessment Comparison Matrix

Overwhelmed by all of the choices and assessment varieties? Included is a handy reference chart that will help in the decision making process.

Assessment Comparison Matrix