Contact lenses are medical devices that require a specific prescription to ensure both clear vision and the health of your eyes. While it is possible to walk out with lenses in hand on the same day, this ability is strictly governed by whether you meet a few non-negotiable requirements.
The Necessity of a Current Contact Lens Prescription
Obtaining contact lenses requires a valid prescription that is distinct from a prescription for eyeglasses. The Federal Trade Commission (FTC) mandates that eye care providers must release this prescription to you upon completion of a fitting, allowing you to purchase lenses from any vendor. This prescription is legally required because contact lenses sit directly on the delicate surface of the eye, making the physical fit as important as the power correction.
The contact lens prescription includes specific technical parameters that an eyeglass prescription does not, such as the base curve (BC) and the diameter (DIA). The base curve measures the curvature of the lens in millimeters and ensures the lens sits properly on your cornea. The diameter specifies the size of the lens, which is typically larger for soft lenses compared to hard lenses.
Federal regulations require contact lens prescriptions to be valid for at least one year from the date of issue, though some state laws may allow for a longer period. Using an expired prescription or one not specifically for contacts can lead to lenses that are too tight or too loose, potentially causing discomfort, blurry vision, or even damage to the eye’s surface.
Immediate Availability: Inventory and Trial Lenses
Receiving a full supply of lenses on the same day depends on what the provider has in stock. Eye care practices often maintain an inventory of “diagnostic sets” or “revenue boxes” for the most commonly requested lenses. This stock typically focuses on spherical lenses, which correct simple nearsightedness or farsightedness, in the most common power ranges.
For patients with common prescriptions, providers are more likely to have a supply of popular brands ready to dispense immediately. This same-day service is a convenience that many practices offer to enhance patient satisfaction and promote loyalty. However, this in-office stock is usually limited to the most used parameters of high-volume lenses, such as daily or two-week disposables.
The immediate availability significantly decreases for specialty lenses. These lenses have a much wider range of parameters, including cylinder and axis values for astigmatism correction, making it impractical for a practice to keep every combination in stock. In these cases, you may receive a limited number of trial lenses to wear while your full order is placed and shipped.
Getting Contacts Without a Current Prescription
If you do not have a current contact lens prescription, the process is multi-stepped and generally precludes receiving a full supply on the same day. It requires a comprehensive eye examination to determine your baseline vision correction needs, followed by a separate contact lens fitting. This fitting involves precise measurements of your eye’s surface.
During the fitting, the eye care professional measures your corneal curvature and assesses the quality of your tear film. These measurements dictate the necessary base curve and diameter of the lens selected. A trial lens is then placed on your eye to evaluate its fit, movement, and visual performance.
After the initial fitting, a mandatory trial period is necessary to ensure the lenses are comfortable and not negatively impacting your eye health. A follow-up check is required before the final prescription can be finalized and released. This appointment allows the doctor to make any necessary adjustments to the lens type or parameters, preventing the final prescription from being issued on the same day as your initial exam.