I’m not very familiar with the world of contact lenses. I wear glasses exclusively. But many people who wear contact lenses also wear glasses part-time. Until recently, it was common practice for ophthalmologists to refuse to give contact lens wearers their own prescription after fitting them. This meant that if he went to have contact lens tests done, he would be forced to continue buying contact lenses from that ophthalmologist in the future, because they would not release his prescription. Ophthalmologists, of course, feared that their patients would receive contacts in the mail in the future.
A law was passed, titled the “Contact Lens Consumer Fairness Act” that requires your eye doctor to provide your contact lens prescription after fitting your contact lenses.
How does this apply to glasses? You can use your prescription for your contact lenses to fill a prescription for eyeglasses. Therefore, you can use your contact lens prescription to order glasses online. Please note, however, that you may NOT use an eyeglass prescription to fill a contact lens prescription. This is because a contact lens prescription has additional information about the shape of the eye.
As a side note, your ophthalmologist also cannot refuse to provide you with a prescription for glasses, but this law has been around since the 1970s. So if a particular optometrist has fitted your glasses, your doctor is legally required to provide your prescription. when requested. Don’t let an optometrist say, “we can’t/won’t provide that information.” You have a legal right to your own prescription.
At The Consumerist, a blogger provides a few more details.