Understanding Contact Lens Prescription: Glossary, Tips, and Recommendations

Wearing contact lenses is a convenient and popular vision correction option, but understanding your contact lens prescription is essential for optimal eye health and clear vision. In this guide, we’ll delve into the intricacies of contact lens prescriptions, offering insights, tips, and recommendations to help you navigate this essential aspect of eye care. Please read on. 

What Does a Contact Lens Prescription Look Like?

A contact lens prescription is a unique set of specifications provided by your eye care professional to ensure the proper fit and correction for your eyes. It includes details such as lens power, base curve, diameter, and, if applicable, the brand and material of the lenses. Understanding each component is crucial for obtaining the right lenses for your eyes.

Below is an illustration of a contact lens prescription for your reference:

A sample of a contact lens prescription

Can I Use My Eyeglass Prescription for Contacts?

No. While eyeglass and contact lens prescriptions share some similarities, they are not interchangeable. Contact lenses sit directly on the eye, requiring specific measurements that differ from those for eyeglasses. Using the wrong prescription can lead to discomfort and vision issues, underscoring the importance of having a dedicated contact lens prescription.

How Do You Get a Contact Lens Prescription?

Any type of contact lens cannot be sold in the U.S. without a valid prescription. Hence, you must secure one when planning to purchase contact lenses online or from any retailer.  

For your convenience, here is the step-by-step process for getting a valid contact lens prescription:

  • Eye Examination

Call and schedule an appointment with an optometrist or ophthalmologist for an eye examination. During the exam, the eye care professional will conduct a comprehensive assessment of your vision, eye health, and suitability for contact lenses.

  • Measurement of Prescription 

Specific measurements will be taken to determine the prescription, including refractive power (SPH), cylinder (CYL) for astigmatism, and additional parameters if needed.

  • Trial Lenses 

In some cases, the eye care professional may provide trial lenses to assess comfort and effectiveness before finalizing the prescription. The optometrist or ophthalmologist will discuss the prescription with you, addressing any questions or concerns you may have. Always communicate your experience to your eye doctor to ensure an accurate and comfortable prescription. 

  • Prescription Issuance 

Once the prescription is finalized, a written prescription will be issued, specifying details such as lens power, base curve, diameter, and other relevant information.

  • Follow-Up Exams

Regular follow-up exams are recommended to monitor eye health, ensure the prescription remains accurate, and make any necessary adjustments over time.

What Is Considered a High Contact Lens Prescription?

A high contact lens prescription typically involves a significant degree of nearsightedness, farsightedness, or astigmatism. The prescription strength is measured in diopters, with higher numbers indicating more severe refractive errors. Monthly soft contact lenses are typically designed for prescriptions up to approximately -12 diopters, with toric lenses accommodating prescriptions up to approximately -9 diopters. It’s essential to note that the average prescription for nearsightedness, or myopia, hovers around -2 diopters. Individuals with high prescriptions may require specialized contact lenses or alternative vision correction options.

Understanding Contact Lens Prescription: Glossary of Terms and Abbreviations

Navigating a contact lens prescription often involves deciphering a range of terms and abbreviations. This section will provide a comprehensive glossary, breaking down common terms used by eye care professionals.

  • ADD (Addition): This refers to the additional magnifying power in multifocal lenses, specifically for reading or close-up vision. It ensures that individuals with presbyopia, a condition where the eyes gradually lose the ability to focus on close objects, can see clearly at different distances.
  • AXIS: This specification denotes the orientation of the cylindrical correction for astigmatism. It is measured in degrees from 0 to 180, indicating the angle where the astigmatism correction is most effective. Understanding the axis is crucial for accurately addressing astigmatism and achieving optimal vision correction.
  • BC (Base Curve): The base curve is a critical measurement describing the curvature of the lens. It ensures that the contact lens fits seamlessly onto the surface of the eye. Measured in millimeters, typically between eight and 10, this value is essential for selecting the right size of prescription contact lenses that perfectly accommodate the corneal size.
  • CYL (Cylinder): The cylinder measurement represents the amount of astigmatism correction needed. Astigmatism occurs when the cornea or lens has an irregular shape, causing distorted or blurred vision. The cylinder value, combined with the axis, addresses this condition by specifying the degree of correction required.
  • D (Diopters): Diopters are the unit of measurement for lens power. Whether correcting myopia (nearsightedness) or hyperopia (farsightedness), the diopter value indicates the strength of the prescription. A higher numerical value signifies a stronger prescription.
  • DIA (Diameter): The diameter measurement indicates the width of the contact lens, expressed in millimeters. It plays a crucial role in determining where the lens will sit on the eye’s surface. An accurate diameter measurement is essential to prevent discomfort and potential scratching caused by improperly sized lenses.
  • OD (Oculus Dexter): Translated from Latin, O.D. stands for “right eye.” This identifier is fundamental in distinguishing the prescription for the right eye.
  • OS (Oculus Sinister): Translated from Latin, O.S. stands for “left eye.” This identifier is crucial for specifying the prescription for the left eye.
  • OU (Oculus Uterque): Translated from Latin, O.U. stands for “both eyes” or “each eye.” When present on a prescription, it indicates that the same measurement applies to both eyes.
  • PL (Power or Plano): This indicates that no vision correction is needed, signifying that the lens has zero power. It is commonly used when individuals require contact lenses for cosmetic purposes rather than vision correction.
  • PWR (Refractive Power): Also known as SPH (sphere), PWR represents the refractive power needed for vision correction. Measured in diopters, this value indicates the correction required to achieve 20/20 vision or the closest possible.
  • R (Radius): Similar to the base curve, the radius denotes the curvature of the lens. It is crucial to ensure that the lens fits the natural curvature of the eye.
  • SPH (Sphere): SPH indicates the lens power needed to correct myopia (nearsightedness) or hyperopia (farsightedness). The numerical value, along with the sign (+ or -), specifies the strength of the prescription.
  • TORIC: Toric lenses are specifically designed to correct astigmatism. The toric designation ensures that the lens has the necessary shape to address astigmatism effectively.
  • UV: This specification indicates whether the lenses have ultraviolet (UV) protection. UV protection is crucial for safeguarding the eyes from harmful ultraviolet rays, contributing to overall eye health.

Are Daily and Monthly Contacts the Same Prescription?

Daily and monthly contact lenses serve different purposes, and their prescriptions may not be identical. Daily lenses are designed for single use and are disposed of after each wear, while monthly lenses are worn for a more extended period before replacement. Understanding these distinctions ensures you choose the right type of lens for your lifestyle and vision needs.

How Long Can I Use My Contact Lens Prescription?

Contact lens prescriptions have expiration dates, and you need to adhere to them for continued eye health. The expiration is determined by your eye care professional based on factors such as your eye health, prescription stability, and the type of lenses prescribed. Regular eye exams are essential for updating your prescription and ensuring optimal vision correction.

Key Takeaway

In essence, understanding a contact lens prescription is an empowering one, allowing individuals to take charge of their eye health and vision correction. The comprehensive glossary, coupled with tips and recommendations, serves as a guide for navigating the technicalities of prescriptions, fostering a sense of confidence in making wise decisions about contact lens choices. Always prioritize eye care and adhere to prescribed guidelines to ensure a seamless and comfortable experience everyday.