If you have a current progressive or bifocal prescription, you may see a distance prescription and an ADD value. The ADD describes additional plus power for near tasks, such as reading. Understanding how these numbers relate can help you read your prescription, but it does not replace an eye examination or a complete prescription review.
Presbyopia, Reading Glasses and Your Prescription
Presbyopia is an age-related change that makes close objects harder to focus on. It is different from farsightedness, also called hyperopia. A person can have presbyopia together with myopia, hyperopia or astigmatism.
Reading glasses may provide near-vision correction only. Bifocal and progressive lenses combine near-vision correction with distance correction in the same pair of glasses. The right option depends on your prescription and the tasks you need to perform.
How to Read the Main Prescription Terms
| Prescription Term | What It Describes | Why It Matters for Near Vision |
|---|---|---|
| SPH | The spherical lens power for each eye. | For a multifocal prescription, the distance SPH is used with the ADD to describe near-vision power. |
| ADD | Additional plus power prescribed for close work. | It is commonly used for the near portion of bifocal or progressive lenses. |
| CYL and Axis | Values used to correct astigmatism. | They may still be required for custom prescription reading glasses and should not be changed without guidance. |
| PD | Pupillary distance measurement. | It is a fitting measurement, not usually part of the written prescription, and may be needed when ordering glasses. |
For a fuller explanation of prescription abbreviations, see How to Read Your Prescription.
Understanding the SPH + ADD Relationship
For a current multifocal prescription, the near sphere can be explained using this relationship for each eye:
Distance SPH + signed ADD = Near SPH
This is an educational explanation of how the near component relates to the distance component. It is not a universal self-conversion method. The correct near prescription can also depend on your working distance, lens design, eye health, binocular vision and other prescription details.
Example: A Minus Distance Prescription
If one eye has a distance SPH of -1.75 and an ADD of +2.25, the arithmetic result is +0.50:
-1.75 + (+2.25) = +0.50
Example: A Plus Distance Prescription
If one eye has a distance SPH of +3.00 and an ADD of +1.75, the arithmetic result is +4.75:
+3.00 + (+1.75) = +4.75
Calculate each eye separately. If CYL and Axis appear on your prescription, do not assume that they can be omitted for custom readers. Ask an eye-care professional or qualified optical provider to review the complete prescription before ordering.
When a Simple Conversion Is Not Enough
A formula alone may not give you the right glasses when your prescription includes astigmatism, prism, unequal values between the two eyes, progressive lens requirements or a recent change in vision. It is also not a replacement for a new eye examination when your current glasses no longer provide clear or comfortable vision.
Ready-made reading glasses may work for some people with simple and similar near-vision needs in both eyes. They do not correct differences between eyes, astigmatism, prism or other custom prescription requirements.
Ordering Prescription Reading Glasses
- Use a current prescription issued by your eye-care professional.
- Check whether you need single-vision reading lenses, bifocals or progressive lenses.
- Enter the prescription values exactly as written for each eye.
- Review frame size and the available lens options before ordering.
- Contact an eye-care professional if you are unsure whether your prescription is suitable for reading-only glasses.
Explore prescription eyeglasses, bifocal glasses, and progressive glasses to compare available options.
Frequently Asked Questions
Can I convert my distance prescription to reading glasses?
A current multifocal prescription may show a distance SPH value and an ADD value for near vision. Adding the signed ADD to the distance SPH for each eye can help explain how a near-vision prescription is derived. However, this is not a substitute for an eye examination or a complete prescription review.
Do I keep CYL and Axis on a reading glasses prescription?
If your prescription includes CYL and Axis, they may still be needed for custom prescription reading glasses. Do not remove or change them without guidance from an eye-care professional or qualified optical provider.
Is presbyopia the same as farsightedness?
No. Presbyopia is an age-related loss of near focusing ability. Farsightedness, also called hyperopia, is a separate refractive error. A person can have presbyopia along with myopia, hyperopia or astigmatism.
Can I use over-the-counter reading glasses instead of prescription readers?
Over-the-counter readers may work for some people with simple, equal near-vision needs in both eyes. They do not correct differences between eyes, astigmatism, prism or other prescription requirements. Regular eye examinations are important to confirm that your vision needs are being addressed.
