2 doctors weighed in:

How do they test on an eye reading chart; what do the numbers mean?

2 doctors weighed in
Dr. Alan Ali
Psychiatry
1 doctor agrees

In brief: Eye chart

They test visual acuity to determine type of glasses or contacts you might need.

In brief: Eye chart

They test visual acuity to determine type of glasses or contacts you might need.
Dr. Alan Ali
Dr. Alan Ali
Thank
Dr. David Chandler
Ophthalmology

In brief: Visual acuity

The numbers 20/20, 20/25, etc.
Are a measurement of visual acuity. It has been found that a normal human eye should be able to discriminate a spatial pattern separated by a visual angle of 1 minute of arc. This translates to a 20/20 letter being 8.87 mm high at 20 feet. If that image can be seen, the vision is 20/20. Larger letters are in proportion. The "20" on top is the testing distance.

In brief: Visual acuity

The numbers 20/20, 20/25, etc.
Are a measurement of visual acuity. It has been found that a normal human eye should be able to discriminate a spatial pattern separated by a visual angle of 1 minute of arc. This translates to a 20/20 letter being 8.87 mm high at 20 feet. If that image can be seen, the vision is 20/20. Larger letters are in proportion. The "20" on top is the testing distance.
Dr. David Chandler
Dr. David Chandler
Thank
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