How to Read Your Eyeglasses Prescription

Your eyeglasses prescription uses standardized abbreviations to specify the exact lens power each eye needs. OD and OS identify the right and left eye, SPH corrects nearsightedness or farsightedness, CYL and AXIS correct astigmatism, ADD provides reading correction for presbyopia, and PD ensures the lenses are centered over your pupils. Negative SPH values indicate myopia; positive values indicate hyperopia. Once you understand these six fields, you can verify any prescription and make informed decisions about your lenses.

This guide breaks down each field on a standard eyeglasses prescription with worked examples, so you can identify your type of refractive error and confirm that your prescription is complete before ordering lenses.

Anatomy of an Eyeglasses Prescription

A standard eyeglasses prescription follows an internationally recognized format. Every valid prescription includes these elements:

• Patient information: Full name, date of birth
• Prescriber information: Name, license number, signature
• Prescription date: Required to verify that the prescription has not expired
• OD (right eye) and OS (left eye): Listed on separate lines
• Correction fields: SPH, CYL, AXIS organized in columns
• Pupillary Distance (PD): Often listed separately or measured at the optical shop
• Special notes: Lens type recommendations, usage restrictions

Under the FTC Eyeglass Rule, your eye doctor must provide you with a copy of your prescription at no extra charge immediately after your exam. Prescription expiration varies by state, but eyeglass prescriptions are typically valid for one to two years.

Prescription Abbreviation Reference Table

Here is a quick-reference table covering every standard abbreviation you will find on an eyeglasses prescription:

How to Interpret Each Field on Your Prescription

Sphere (SPH): Myopia and Hyperopia Correction

The sphere (SPH) column represents the lens power needed to fix your vision, according to the American Academy of Ophthalmology. A minus sign (-) indicates myopia (nearsightedness), and a plus sign (+) indicates hyperopia (farsightedness). Lens power is measured in diopters (D).

For example, -2.00 SPH means 2 diopters of nearsighted correction. The higher the number, the stronger the correction: -6.00 is a stronger prescription than -2.00.

Classification by severity:

• Myopia: Mild (-0.25 to -3.00), moderate (-3.25 to -6.00), high (beyond -6.00)
• Hyperopia: Mild (+0.25 to +2.00), moderate (+2.25 to +4.00), high (beyond +4.00)

Cylinder (CYL) and Axis: Astigmatism Correction

The cylinder number indicates how much astigmatism you have, and the axis specifies the orientation of the correction. CYL values are written in diopters, while the axis is written in degrees from 1 to 180.

For example, -1.25 CYL at 180 means 1.25 diopters of astigmatic correction along the horizontal meridian. The National Eye Institute defines astigmatism as a condition in which “the eye does not focus light evenly onto the retina”, causing images to appear blurry or distorted at any distance.

Understanding the axis: 90 degrees represents the vertical meridian, 180 degrees represents the horizontal, and 45 or 135 degrees represent the diagonals. Even a 5 to 10 degree error in axis orientation can noticeably degrade visual clarity, which is why precise measurement is critical.

Addition (ADD): Near-Vision Correction for Presbyopia

For multifocal or progressive prescription lenses, the ADD field specifies the extra power needed for reading and close work. This value is always positive and is added to the distance SPH value to calculate the near-vision correction.

Presbyopia typically begins between the ages of 40 and 45 and progresses through the sixth decade, according to StatPearls. ADD values range from +0.75 for mild presbyopia to +2.50 or greater for advanced cases, increasing by approximately +0.25 diopters every two years between ages 40 and 50.

Pupillary Distance (PD): Lens Centering

PD is the distance between the centers of your pupils, measured in millimeters. It determines where the optical center of each lens should be positioned. Typical adult PD values range from 54mm to 74mm.

An incorrect PD can cause headaches, eye strain, and discomfort even when the prescription power is correct. For progressive lenses, PD accuracy is especially critical because the reading zone, intermediate zone, and distance zone all depend on precise centering. ANSI Z80.1 specifies a tolerance of +/-2.5mm for near interpupillary distance in finished eyewear.

PD is not always included on the prescription itself. If yours does not list it, your optician will measure it before fabricating your lenses, or you can use a remote PD measurement tool.

Identifying Your Refractive Error From the Prescription

You can determine your type of vision correction by looking at which fields are filled in:

Myopia (nearsightedness): SPH has a negative value (e.g., -2.00). CYL is empty or marked “plano.” The NEI defines myopia as a condition that “makes far-away objects look blurry.”

Hyperopia (farsightedness): SPH has a positive value (e.g., +1.50). CYL is empty or marked “plano.”

Astigmatism: CYL field has a value (with an accompanying AXIS). Can appear with or without myopia or hyperopia. If SPH is marked “plano” or 0.00 with a CYL value present, this is pure astigmatism.

Presbyopia: ADD field has a value. Typically found in patients over 40. Research published in StatPearls notes that more than 80% of individuals aged 40 develop presbyopia.

Common combinations:

• Myopia + astigmatism: Negative SPH with CYL filled in
• Hyperopia + astigmatism: Positive SPH with CYL filled in
• Myopia + presbyopia: Negative SPH with ADD value (requires progressive or bifocal lenses)

Worked Prescription Examples

Example 1: Simple Myopia (Both Eyes)

OD: SPH -2.00 | CYL — | AXIS —
OS: SPH -2.50 | CYL — | AXIS —
PD: 63mm

Reading this prescription: Mild myopia in both eyes, with the left eye slightly stronger (-2.50 vs. -2.00). No astigmatism present. This patient needs glasses for distance activities: driving, watching TV, seeing a whiteboard. Single-vision lenses are sufficient.

Example 2: Hyperopia with Astigmatism

OD: SPH +1.50 | CYL -0.75 | AXIS 90
OS: SPH +1.50 | CYL -0.75 | AXIS 90
PD: 62mm

Reading this prescription: Mild hyperopia (+1.50) combined with mild astigmatism (-0.75) at the vertical meridian (90 degrees) in both eyes. This patient may experience blurry or slightly distorted vision at multiple distances. Full-time wear with single-vision lenses is typical.

Example 3: Multifocal Prescription (Presbyopia)

            DISTANCE                    NEAR
OD: SPH -1.00 | CYL -0.50 | AXIS 180 | ADD +2.00
OS: SPH -1.50 | CYL -0.50 | AXIS 180 | ADD +2.00
PD Distance: 64mm | PD Near: 61mm

Reading this prescription: Mild myopia with astigmatism for distance, plus presbyopia requiring an ADD of +2.00. The effective near-vision power is calculated by adding SPH + ADD: for the right eye, -1.00 + 2.00 = +1.00; for the left eye, -1.50 + 2.00 = +0.50. This patient needs progressive or bifocal lenses. Note that PD is listed separately for distance and near because the eyes converge when focusing on close objects.

Example 4: Astigmatism Only

OD: SPH plano | CYL -1.00 | AXIS 180
OS: SPH plano | CYL -1.00 | AXIS 180
PD: 65mm

Reading this prescription: Pure astigmatism with no myopia or hyperopia. “Plano” (or 0.00) in the SPH column means zero spherical correction is needed. The -1.00 CYL at 180 degrees corrects astigmatism along the horizontal meridian. This patient may notice blurred or ghosted images, especially in low-light conditions.

Understanding the Numbers and Signs

The numbers on your prescription represent diopters, the unit measuring lens refractive power:

Negative values (-): Divergent lenses for myopia correction. A higher absolute number means stronger myopia. -6.00 is significantly stronger than -2.00 and will require thicker lenses. You can estimate the impact on lens thickness using a calculator.

Positive values (+): Convergent lenses for hyperopia or near-vision correction (ADD). +4.00 is stronger than +1.00.

Axis degrees: Range from 1 to 180 and indicate the orientation of astigmatic correction. These are not a measure of severity but of direction.

Increments: Prescriptions change in 0.25 diopter steps (e.g., -1.00, -1.25, -1.50, -1.75, -2.00).

Distance Vision (DV) vs. Near Vision (NV) on a Prescription

Many prescriptions, particularly for patients over 40, are divided into sections:

DV (Distance Vision): The correction for seeing far away. Used for driving, watching screens from a distance, and outdoor activities. In progressive lenses, this corresponds to the upper portion of the lens.

NV (Near Vision): The correction for reading and close work. This equals the distance SPH value plus the ADD value. In progressive lenses, this corresponds to the lower portion.

Intermediate Vision: Some prescriptions specify a separate intermediate correction for computer use and mid-range tasks. This is used for occupational or office lenses.

The relationship is straightforward: if your distance prescription is -1.00 SPH and your ADD is +2.00, your near-vision effective power is +1.00 (-1.00 + 2.00).

Seven Common Mistakes When Reading a Prescription

Avoid these errors when interpreting your eyeglasses prescription:

1. Swapping OD and OS values: Each eye’s correction is specific. Entering the right eye’s values for the left eye (or vice versa) will produce unusable lenses.
2. Missing the positive or negative sign: A prescription of 2.00 without a sign is ambiguous. Always verify whether the value is -2.00 (myopia) or +2.00 (hyperopia).
3. Ignoring the axis: The axis is as important as the CYL value. An incorrect axis will distort vision even if the cylinder power is correct.
4. Using an expired prescription: Under state law, eyeglass prescriptions typically expire after one to two years. An outdated prescription may no longer match your current vision needs.
5. Forgetting to measure PD: Without PD, lenses cannot be properly centered. If your prescription does not include PD, have it measured before ordering, either at an optical shop or with a digital tool like Optogrid’s photo-based measurement system.
6. Confusing ADD with the near-vision power: ADD is not your reading prescription by itself. It is added to the distance SPH to calculate the near-vision correction.
7. Assuming “plano” means no glasses needed: “Plano” in the SPH field only means zero spherical error. The patient may still have astigmatism requiring correction.

Prescription Completeness Checklist

Before ordering lenses, confirm your prescription includes all required information:

• ☑ Patient name clearly identified
• ☑ Prescription date (check that it has not expired per your state’s rules)
• ☑ OD and OS both listed (even if one eye is “plano”)
• ☑ SPH, CYL, AXIS filled in where applicable (if CYL is present, AXIS must be too)
• ☑ PD measured (or plan to have it measured at the optical shop)
• ☑ Prescriber signature and license number legible
• ☑ ADD value included if you need multifocal or progressive lenses
• ☑ All numbers and signs clearly legible (no ambiguous values)

If any required field is missing or illegible, contact your eye care provider for a corrected copy. Under the FTC Eyeglass Rule, you have the right to receive a complete, legible prescription.

Prescription Examples by Vision Condition

Myopia Prescription

Myopia is corrected with divergent (minus) lenses. A prescription of -3.00 SPH means the patient needs 3 diopters of correction to see clearly at distance. The higher the negative number, the greater the difficulty seeing distant objects. For high myopia prescriptions (beyond -6.00), higher-index lens materials reduce both thickness and weight. Effective myopia management strategies are especially important for children, where progression can be slowed with specialized lenses.

Hyperopia Prescription

Hyperopia is corrected with convergent (plus) lenses. A prescription of +2.00 SPH provides 2 diopters of correction. While hyperopia primarily affects near vision, high degrees of hyperopia (beyond +4.00) can blur distance vision as well.

Astigmatism Prescription

Astigmatism requires cylindrical lenses. The prescription includes both a CYL value (the power of correction) and an AXIS (the orientation). For example, -1.50 CYL at 90 means 1.50 diopters of correction along the vertical meridian. Astigmatism causes blurred or distorted vision at all distances.

Multifocal Prescription

Patients who need both distance and near correction receive a multifocal prescription with an ADD value. For example, an ADD of +2.00 means 2 additional diopters are layered onto the distance correction for reading. Progressive lenses provide a smooth transition between distance, intermediate, and near zones, while bifocal lenses have a visible line separating two distinct zones.

Frequently Asked Questions

How Optogrid Helps With Prescription Measurements

If your prescription is missing the PD value, or if you need to verify your measurements before ordering lenses online, Optogrid’s digital measurement tool can help. The system calculates PD from photos taken with a standard smartphone, producing results with a margin of error under 1mm.

This is particularly useful for optical shops offering remote services, and for patients who need accurate measurements without an in-person visit. The tool works with both single PD and monocular PD measurements, and its accuracy is comparable to traditional digital pupillometers.

Sources and References

• American Academy of Ophthalmology: How to Read an Eyeglasses Prescription
• National Eye Institute: Refractive Errors
• StatPearls (NCBI): Presbyopia
• FTC Eyeglass Rule
• ANSI Z80.1 Quick Reference

Saulo Garcia

I am a seasoned software engineer with over two decades of experience and a deep-rooted background in the optical industry, thanks to a family business. Driven by a passion for developing impactful software solutions, I pride myself on being a dedicated problem solver who strives to transform challenges into opportunities for innovation.