Snellen chart
ProductMentioned in 2 videos
A chart with letters of decreasing size, used to test visual acuity.
Videos Mentioning Snellen chart

198 - Eye health—everything you need to know | Steven Dell, M.D.
Peter Attia MD
A standard measurement of visual acuity, where 20/20 means seeing at 20 feet what a normal person sees at 20 feet. 20/10 is better, meaning seeing at 20 feet what normal sees at 10 feet.

Protocols to Improve Vision & Eyesight | Huberman Lab Essentials
Andrew Huberman
A chart with letters of decreasing size, used to test visual acuity.