Snellen & Astigmatism

Snellen Eye Chart

20/20

Average decent vision requiring little correction.

An individual with 20/20 vision does not have perfect eyesight.

WORSE than 20/20
An individual with 20/40 vision must stand at 20 feet to see what an individual with 20/20 vision can see at 40 feet.

BETTER than 20/20:
An individual with 20/15 vision can stand at 20 feet to see what an individual with 20/20 vision can see at 15 feet.

Astigmatism

• Often referred to as "out-of-round."
• Think of squeezing a tennis ball that has been cut in half.
• Are the lines evenly spaced among the rays below ??