Final answer:
A contact lens prescription is generally valid for one year, but may vary depending on the country and the eye care professional.
Step-by-step explanation:
A contact lens prescription is typically valid for a year from the date it was written. However, the specific length of validity may vary depending on the country and the eye care professional who issued the prescription. It is important to follow the instructions provided by the eye care professional and have regular check-ups to ensure the prescription is still suitable for your eyes.