Eye care
The difference between acuity, prescription strength and overall vision.
Last updated November 3, 2026 · General information only, not medical advice. Please see a licensed eye-care professional for your prescription and eye health.
Visual acuity describes how clearly you can see detail at a given distance, typically measured with a letter chart. It is expressed as a fraction such as 20/20 (or 6/6 in metric).
Acuity and prescription strength are different: acuity describes how well you see, while your prescription describes the lens power needed to improve it.
See also Snellen eye chart facts.
Frame shapes, sizes and lens materials that keep strong prescriptions looking slimmer.
Common, general reasons why vision can feel less sharp in low light, and when to see a professional.
How flexible spending and health savings accounts generally apply to prescription eyewear.
How light-adaptive lenses react to UV light and what to check on the label.
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