Usually valid for one to two years (varies by state). Buying Online vs. In-Office
💡 Your glasses prescription is not the same as your contact lens prescription. Because contacts sit directly on the eye while glasses sit about 12mm away, the "power" and measurements are different. If you'd like, I can help you: Find highly-rated eye doctors in your area. Compare the average cost of popular contact lens brands. do you need a prescription to buy contacts
The specific manufacturer or lens type prescribed. Usually valid for one to two years (varies by state)
Eyes vary in shape. An eye doctor must measure the base curve and diameter to ensure the lens doesn't scratch the cornea or cut off oxygen. these are illegal and dangerous.
Avoid "flea market" or "costume shop" lenses that don't ask for a prescription; these are illegal and dangerous.