Reading an eyeglasses prescription can initially seem like deciphering a complex code, but once you understand the terminology and abbreviations, it becomes much clearer. Here’s a guide to help you understand the various components of an eyeglass prescription:

1. Sphere (SPH)

• What it means: The sphere indicates the lens power, measured in diopters, needed to correct nearsightedness or farsightedness. If the number is preceded by a minus sign (-), it means you are nearsighted; if it is preceded by a plus sign (+), you are farsighted.
• How it appears: Numbers like -2.00 or +1.50.

2. Cylinder (CYL) and Axis

• What they mean: These values are related to astigmatism correction. The cylinder indicates the amount of lens power for astigmatism, and like SPH, it is measured in diopters. The axis denotes the orientation of the astigmatism, measured in degrees from 1 to 180.
• How they appear: CYL: -1.25, Axis: 90.

3. Add

• What it means: This is the added magnifying power applied to the bottom part of multifocal lenses to correct presbyopia. The number appears as a “+”, indicating how much power is added to the distance prescription.
• How it appears: +2.00.

4. Pupillary Distance (PD)

• What it means: PD is the distance in millimeters between the centers of the pupils in your eyes. This measurement is crucial for properly aligning your lenses with your eyes.
• How it appears: It might be noted as a single number (e.g., 62) or two numbers (e.g., 31/30.5) if the measurement is taken for each eye separately.

5. Prism

• What it means: This part of the prescription is used to correct eye alignment problems. It’s measured in prism diopters (indicated by “p.d.” or a triangle symbol) and indicates the amount of prism needed to correct eye alignment issues.
• How it appears: 2Δ base up (BU), 2Δ base in (BI), etc.

Additional Abbreviations

• OD (Oculus Dexter): Right eye.
• OS (Oculus Sinister): Left eye.
• OU (Oculus Uterque): Both eyes.

Example Prescription

• OD: -2.00 (SPH) -1.25 (CYL) x 90 (Axis)
• OS: -1.00 (SPH) -0.75 (CYL) x 85 (Axis)
• Add: +2.00 (for both eyes, indicating bifocals or progressives)
• PD: 62

Key Tips for Reading Your Prescription

1. Understand the Basics: Familiarize yourself with the basic terms (SPH, CYL, Axis, Add, PD) to better understand your needs.
2. Ask Questions: If any part of your prescription is unclear, don’t hesitate to ask your eye care professional for clarification.
3. Accuracy is Crucial: When ordering glasses, ensure all details are entered correctly. Mistakes can lead to discomfort and improper vision correction.

Understanding your eyeglasses prescription is the first step in finding the perfect pair of glasses that not only corrects your vision but also fits your lifestyle and aesthetic preferences. If you’re ever in doubt, consult with your optometrist or an optical professional to clarify any confusion and ensure your eyewear is perfectly tailored to your vision needs.