A contact lens prescription is a document containing specific measurements that ensure the lenses not only correct your vision but also fit the unique physical contours of your eye. This guide provides practical instruction for retrieving this information and understanding the meaning of the technical measurements, allowing you to confidently manage your vision correction needs.
Your Legal Right to the Prescription
Federal law grants you the right to a copy of your prescription immediately after a contact lens fitting, regardless of whether you ask for it. This right is governed by the Contact Lens Rule, which requires eye care providers to automatically release the prescription to the patient.
This mandate prevents providers from requiring you to purchase lenses directly from them. The release of the prescription must happen at the end of the fitting process, even if you have not yet paid for the eye examination. If you need an additional copy later, providers are required to supply it within a reasonable timeframe, usually within 40 business hours of your request. You can request the document by contacting the provider’s office via phone, email, or through their secure patient portal.
Finding the Information on Packaging
You can find the necessary details printed on the product packaging itself. The exterior of the contact lens box contains the fundamental parameters required for reordering the same lens. Look for a series of abbreviations and numbers printed directly on the box.
The individual foil blister packs that house each lens also have the prescription information abbreviated on the seal. This information usually includes the lens brand, power, and physical dimensions. The data on the packaging may be slightly condensed compared to the comprehensive information on the official prescription form. You may also be able to retrieve past prescription details from receipts or order histories within an online patient portal or retailer account if you have purchased lenses previously.
Understanding the Prescription Details
The Sphere (SPH), sometimes labeled as Power (PWR), is a measurement expressed in diopters that indicates the main strength of the lens needed to correct your nearsightedness or farsightedness. A minus sign (-) denotes correction for nearsightedness, while a plus sign (+) indicates correction for farsightedness.
The Base Curve (BC) and Diameter (DIA) are physical measurements of the lens. The Base Curve, measured in millimeters, refers to the curvature of the lens and is designed to match the curvature of your cornea for a proper, comfortable fit. The Diameter, also in millimeters, specifies the overall size of the lens from edge to edge, ensuring it adequately covers the cornea.
For individuals with astigmatism, two additional measurements are required. The Cylinder (CYL) indicates the amount of extra power needed to correct the astigmatism. This value is usually a negative number. The Axis (AX) is a number between 0 and 180 degrees that specifies the orientation of the Cylinder power on the eye.
If you use multifocal or bifocal lenses, your prescription will also include an Add Power (ADD) value. This measurement represents the additional magnifying power needed for near vision.
When the Prescription Requires Renewal
A contact lens prescription must be renewed through a comprehensive examination after a specific period. In the United States, federal law requires that a contact lens prescription be valid for a minimum of one year. However, state laws can extend this validity period, with some jurisdictions allowing prescriptions to remain active for up to two years.
Vision can change over time, and regular examinations are necessary to ensure the lenses still provide accurate correction. The renewal process is also a chance for the eye care provider to evaluate the overall health of your eyes, checking for any developing conditions or issues related to lens wear. Wearing lenses with an outdated prescription can lead to discomfort or strain.