It is not possible to legally or safely obtain contact lenses without first visiting an eye doctor for a comprehensive exam and a valid, current prescription. Contact lenses are highly regulated medical devices that sit directly on the surface of the eye, not simple cosmetic accessories. Because they interact closely with the eye’s delicate biological structures, a professional fitting and prescription is mandatory to ensure both vision correction and eye health.
Why a Prescription is Legally Required
Contact lenses are classified as medical devices by the U.S. Food and Drug Administration (FDA) because they introduce a foreign object to the eye’s surface. This classification subjects them to strict regulatory oversight to prioritize patient safety and effectiveness, and federal law mandates that lenses can only be sold pursuant to a valid, non-expired prescription.
The Federal Trade Commission (FTC) enforces this requirement through the Contact Lens Rule, which ensures consumers receive their prescription to purchase lenses from any vendor they choose. Sellers are required to verify the prescription with the eye doctor before fulfilling an order, which acts as a safeguard against using expired or incorrect prescriptions.
The Essential Role of the Contact Lens Exam
A contact lens exam is a separate process from a standard vision exam for eyeglasses, and an eyeglass prescription is insufficient for purchasing contacts. This is because glasses sit away from the eye, while a contact lens rests directly on the cornea, requiring the optical power to be adjusted for proximity.
The eye doctor performs specific measurements to ensure the lens fits the unique curvature of the patient’s eye. They use instruments like a keratometer to measure corneal curvature, determining the necessary base curve, and also measure the iris and pupil diameter to select the appropriate lens size. Beyond physical measurements, the doctor assesses the health of the tear film to determine the safest and most comfortable lens material. The final prescription includes the power, specific lens brand, material, base curve, and diameter.
Dangers of Using Lenses Without Professional Guidance
Purchasing lenses without a proper fitting can lead to serious and potentially permanent eye health complications. An ill-fitting lens, whether too tight or too loose, can cause corneal abrasions (scratches on the eye surface) that create an entry point for bacteria and quickly develop into a severe infection.
One concerning risk is microbial keratitis, a serious corneal infection that can result from improper fit or using lenses from unregulated sources. This condition can cause extreme pain, require hospitalization, and may lead to extensive corneal scarring or even the loss of an eye. Another danger is corneal hypoxia, where a lens deprives the cornea of sufficient oxygen, causing swelling, blurred vision, and the abnormal growth of blood vessels (neovascularization).