How to Read the Prescription and Choose the Right Glasses？

An eye prescription is a medical record that specifies how lenses should correct your vision for accuracy and comfort. It includes numbers like sphere (SPH), cylinder (CYL), axis, and pupillary distance (PD). Each value shows how light focuses on the retina for clear vision. Measured in diopters (D), these values define whether you need single vision, bifocal, or progressive lenses.

Understanding these details is key to correcting myopia, hyperopia, or astigmatism. It also helps you pick the right lens material, thickness, and frame style. Reading your prescription accurately is key to choosing glasses that offer clear vision and comfort for daily use.

What Is an Eye Prescription and Why Do You Need It?

An eye prescription is a document from an optometrist or ophthalmologist. It shows the lens power and the type of correction needed for clear vision. The prescription is specific to the eye's optical condition. It explains how light should bend to focus correctly on the retina. Technically, each measure on a prescription is there to fix one of myopia (nearsightedness), hyperopia (farsightedness), astigmatism (the cornea is not uniformly curved), and presbyopia (the eye is not able to focus because of age).

Getting the right prescription is key before buying glasses. This ensures the lenses fit your eyes' needs. It helps prevent eye strain, blurred vision, and headaches. Lenses that match your prescription improve visual clarity. They help keep depth perception and focus normal. This is essential for everyday tasks like reading, driving, and working on a computer.

Example of a Complete Eye Prescription

Below is a sample of a standard eyeglass prescription with key parameters and their meanings:

Each value is quantified in diopters (D) or millimeters, allowing lens manufacturers to produce eyewear tailored precisely to the wearer’s optical measurements.

Eye Prescription Terms Explained

An eye prescription is full of abbreviations that denote the manner in which each lens is to correct the vision of the wearer. Each term is linked to a quantifiable optical characteristic - from power and curvature to the alignment of the lens. Knowing these figures is the main way to make sure that the correction of the vision is precise and that the glasses will be comfortable to wear.

SPH – Sphere Power Meaning

Sphere (SPH) indicates the main lens power required to correct myopia or hyperopia, measured in diopters (D).

• A negative value (–) corrects myopia, or nearsightedness, a condition where the eyeball is slightly elongated, causing light to focus in front of the retina.
  

• A positive value (+) corrects hyperopia, or farsightedness, where light focuses behind the retina because the eyeball is too short or the cornea too flat.

The SPH number is a measure of how the lens needs to be adjusted in terms of optical power so that light is focused properly on the retina again. To illustrate, -1.50D would mean slight nearsightedness, while +2.25D represents moderate hyperopia.

CYL – Cylinder Power Meaning

Cylinder (CYL) is the part of a prescription that indicates the power of the lens that is needed to correct astigmatism. Astigmatism is a feature of the unevenly curved cornea or lens that results in the retina receiving defocused light. Thus, the surface of the eye is not a perfect sphere but rather there is more curvature in one direction which causes the light to scatter and blurred or distorted vision to appear.

CYL shows how much the correction has to be made and it is a pointer that only astigmatism has been taken into account—if there is no such thing, that place will be empty. Generally, the values are between –0.25D and –2.00D. The further away from zero the negative number is, the stronger the correction for astigmatism will be.

Axis – Orientation of Astigmatism

Axis is the feature that describes the direction of the astigmatism correction based on a scale of 0–180°. When the CYL value shows how much correction is necessary, the Axis indicates the location where the correction should be applied. Imagine a protractor: the 180° line is going horizontally, while the 90° line is vertically. The Axis number is the exact angle of the meridian that the optical lab uses to tell the lens where it needs to be to counteract the irregular curvature so that light is focused uniformly over the retina.

ADD – Near Addition Power

Addition (ADD) is the part of the lens power that is only necessary to correct presbyopia, which is the most common type of age-related farsightedness. This is a natural change that occurs when the crystalline lens loses flexibility, and the eye loses its ability to focus on close objects. The ADD numbers are in most cases between +0.75D to +3.00D, and they indicate the level of magnification that is required for reading, computer work, or performing any other close task.

The extra power that is introduced in bifocal and progressive lenses makes it possible to have a smooth visual transition from distance to near vision and therefore, the eye becomes less tired and can concentrate clearly during the usual activities of the ‍‌‍‍‌day.

PD – Pupillary Distance

Pupillary Distance (PD) measures the distance between the centers of both pupils, typically in millimeters (mm). This value is critical because it ensures that the optical centers of the lenses align with the wearer’s pupils, maintaining accurate focus and preventing eye strain or image distortion.

There are two main types of PD:

• Binocular PD: a single number, such as 62mm, representing the total distance between both pupils.
  

• Monocular PD: two separate measurements, such as 30.5/31.5mm, indicating the distance from each pupil to the center of the nose.
  

Accurate PD alignment is essential for both single-vision and multifocal lenses to function properly.

OD, OS, and OU – Eye Notations

In prescriptions, the notations OD, OS, and OU identify which eye the measurements apply to :

• Oculus Dexter (OD): Right eye
  

• Oculus Sinister (OS): Left eye
  

• Oculus Uterque (OU): Both eyes

These Latin terms ensure clarity in optical manufacturing and prevent mix-ups during lens production or fitting.

PL (Plano) – Zero Power Lenses

Plano (PL) is the term that is used to indicate that the lens has zero refractive power. With such a lens, no correction of the vision is necessary. Often, plano lenses are put in the frame of fashionable eyewear or in glasses that filter blue light, thus giving the eyes protection or the user a certain style without changing the vision.

Diopter (D) – The Measurement Unit

The diopter (D) is the fundamental unit that is used to measure the optical power. It is a unit derived from the focal length that is expressed in meters and is therefore the inverse (D = 1/f). For instance, a lens having a power of +2.00D will focus the light at 0.5 meters, whereas a –1.00D lens will do it at 1 meter. Understanding diopters helps users interpret prescription strength and lens curvature in precise, measurable terms.

Eye Prescription Chart: What the Numbers Mean

An eye prescription chart translates numerical lens power into the corresponding degree of vision correction required. Each range of diopter (D) values indicates whether vision issues are mild, moderate, or severe. Understanding these ranges helps users interpret how much correction their lenses provide.

Eye Prescription Power Ranges and What They Mean

Lens power values are measured in diopters (D) and indicate how much the lens must bend light to focus images on the retina.

• –0.25D to –1.00D: Mild myopia — slight difficulty seeing distant objects.
  

• –1.00D to –3.00D: Moderate myopia — distant objects appear blurred; near vision remains clear.

• –3.00D to –6.00D: High myopia — requires stronger correction for clear distance vision.
  

• +0.25D to +1.00D: Mild hyperopia — near tasks cause minor strain.
  

• +1.00D to +3.00D: Moderate hyperopia — noticeable blur when reading.
  

Each range corresponds to how strongly the lens must correct the eye’s refractive error to achieve normal focus.

Is –1.50 Eyesight Bad?

A –1.50D prescription indicates mild to moderate myopia (nearsightedness). Distant objects look a little bit blurred whereas near vision stays clear. Even if it is not a serious condition, this kind of situation normally calls for wearing glasses when driving, or during any activity in which one has to focus at a distance for example watching a presentation or a screen in order to have a clear vision and to avoid eye fatigue.

Is +2.25 Eyesight Bad?

A +2.25D prescription indicates moderate hyperopia (farsightedness). Near objects—such as text or phone screens—may appear blurred, especially in low light or during extended reading. This level of farsightedness generally requires glasses for close-up activities to maintain comfort and headaches caused by over-focusing.

How to Read Eye Prescription Step-by-Step?

Reading an eye prescription means understanding what each value represents and how it affects your lenses. Each component provides exact data that opticians use to create customized vision correction. Follow these steps to interpret it accurately:

• Identify Each Eye: Look for OD (right eye) and OS (left eye). Sometimes you’ll also see OU, meaning both eyes.
  

• Check the SPH Value: This number shows the overall lens power. A negative (–) sign indicates myopia (nearsightedness), while a positive (+) sign indicates hyperopia (farsightedness).
  

• Review the CYL and Axis: CYL measures astigmatism correction power, and Axis (0–180°) tells where that correction applies.
  

• Look for ADD Power: This appears in bifocal or progressive lens prescriptions and shows additional power for close-up focus (used for presbyopia).
  

• Locate PD (Pupillary Distance): Usually listed in millimeters (mm), PD ensures lenses align correctly with your pupils for balanced vision.
  

• Note Special Lens Features: Some prescriptions may include remarks for prism correction, tint, or lens coating preferences.
  

• Confirm Units and Symbols: All power values are in diopters (D); PD is in millimeters (mm). Verify each to avoid errors when ordering lenses.
  

Understanding each component ensures your glasses deliver the exact vision correction your eyes require—preventing strain and maintaining optical accuracy. If you want to understand these components in more detail, you can read our guide What Does Sphere, Cylinder and Axis Mean.

Step 1 — Identify OD and OS (Right and Left Eye)

OD refers to the right eye, OS to the left eye, and OU means both eyes. These notations ensure that each lens matches the correct side during production and fitting. Proper identification maintains balance of vision, allowing both eyes to focus together comfortably and accurately.

Step 2 — Understand SPH (Sphere) Values

Sphere (SPH) indicates the main corrective power of the lens, measured in diopters (D).

• A negative (–) value means myopia, or nearsightedness.
  

• A positive (+) value means hyperopia, or farsightedness.
  

SPH ensures light focuses directly on the retina, providing clear vision at near or far distances depending on the user’s condition.

Step 3 — Read CYL (Cylinder) and Axis for Astigmatism

Cylinder (CYL) measures the power needed to correct astigmatism, which results from an uneven curvature of the cornea or lens.
Axis (ranging from 0° to 180°) shows where that correction should be applied.
Together, CYL and Axis restore balanced light focus on the retina, preventing blurred or distorted images and improving visual precision.

Step 4 — Check ADD for Reading or Progressive Lenses

Addition (ADD) represents the extra magnifying power for near vision, commonly used in bifocal or progressive lenses. This value compensates for presbyopia—a natural, age-related decline in the eye’s ability to focus on close objects—by improving clarity during reading or digital screen use.

Step 5 — Find PD (Pupillary Distance)

Pupillary Distance (PD) measures the distance between the centers of both pupils, typically in millimeters (mm). Accurate PD alignment ensures that each lens’s optical center matches the wearer’s pupils, maintaining correct focus, binocular balance, and comfortable long-term wear.

What Is a Normal Eye Prescription?

A normal eye prescription is plano (0.00D) or near-zero values in both eyes, meaning no refractive correction is required. Vision remains clear at all distances, and glasses are typically worn only for protection or style rather than optical adjustment.

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How Your Eye Prescription Affects Glasses Choice?

The kind of lenses and frames that are most suitable for your vision will be directly determined by your eye prescription. The thickness of your lens, its curve, and the material needed to give the right correction are all influenced by each number — especially the Sphere Power (SPH) and Cylinder (CYL). A stronger prescription usually requires a thinner, stronger material and a smaller, more supportive frame to keep the user comfortable, clear-sighted, and balanced. By making the right choice, your glasses will be the means of accurate vision correction without being heavy or distorted unnecessarily.

Prescription Strength Impacts Lens Thickness

The strength of your prescription affects how thick or thin the lenses must be.

• Higher power lenses (stronger SPH or CYL values) require more curvature to bend light properly, which increases thickness.
  

• To counter this, high-index materials are used; they refract light more efficiently, allowing lenses to stay thinner and lighter.

Recommendation:

• For prescriptions above ±3.00D, choose 1.61 or 1.67 high-index lenses.
  

• For above ±5.00D, use 1.67 or 1.74 high-index lenses to minimize edge or center thickness.
  

Selecting the right index not only improves appearance but also reduces eye strain and frame pressure during daily use.

Choose the Right Lens Material With Glasses Prescription

Lens material determines the optical clarity, durability, and weight of your glasses. Each material has a different refractive index, meaning how much it bends light.

Common Lens Materials and Indexes:

• CR-39 (Standard Plastic): 1.50 index — ideal for mild prescriptions; lightweight and cost-effective.
  

• Polycarbonate: 1.59 index — impact-resistant; recommended for children, sports, and safety glasses.
  

• High-Index Lenses: 1.61, 1.67, 1.74 — thinner, lighter, and suitable for moderate to strong prescriptions.

Recommendation:

For SPH powers above ±3.00D, select 1.61 or 1.67 high-index lenses.
For SPH powers above ±5.00D, use 1.67 or 1.74 to reduce both lens weight and thickness while maintaining sharp optics.

Choosing Frames That Fit Your Prescription Strength

The frame design must support the optical requirements of your prescription. Strong prescriptions fit best in smaller, sturdy frames that minimize lens distortion and weight. For high hyperopia (farsightedness), choose smaller frames to reduce the “magnified-eye” effect at the center. Reinforced or full-rim frames help support thicker lens centers and maintain balance during wear. Avoid rimless, semi-rimless, or oversized frames for strong prescriptions, they make thick lenses more visible and increase overall weight, which may cause slippage or pressure on the nose bridge.

How to Use Your Prescription on GlassesShop.com?

Ordering glasses online is simple when your prescription is ready. Follow these steps to enter it correctly on GlassesShop.com:

• Select Your Frame: Choose from full-rim, semi-rimless, or rimless designs based on your prescription strength.

• Enter Prescription Details: Input your OD, OS, SPH, CYL, Axis, ADD, and PD values exactly as written on your prescription.

• Choose Lens Type: Select single-vision, bifocal, or progressive depending on your vision needs.

• Pick Lens Material and Coatings: Choose the lens index (1.50–1.74) and add options like anti-scratch, anti-glare, or UV protection.

• Preview and Confirm: Review your order summary and verify all numbers before checkout to ensure precise lens manufacturing.

This process guarantees accurate customization, ensuring your new glasses fit your prescription, comfort, and style perfectly.

FAQ

How Long Is an Eye Prescription Valid?

An eye prescription is typically valid for 1–2 years, depending on local regulations and the optometrist’s recommendation. Regular eye exams are essential to detect changes in vision and maintain accurate correction over time.

Can I Use My Glasses Prescription for Contact Lenses?

No. A glasses prescription cannot be used for contact lenses because the two require different parameters and measurements.

• Reason 1: A contact lens prescription includes base curve (BC) and diameter (DIA) to match the lens to the shape of your cornea.
  

• Reason 2: Power conversion is required since glasses sit about 12 mm away from your eyes, while contacts rest directly on them. This difference, known as vertex distance, changes the effective lens power.
  

A separate contact lens fitting ensures proper comfort, oxygen flow, and visual accuracy.

What Does “Spherical Equivalent” Mean?

The spherical equivalent represents the average optical power of an eye when combining sphere and astigmatism correction.

Formula:

SPH + (CYL ÷ 2)

Common Use:

This value is used for simplified lens fittings, such as when prescribing spherical contact lenses for mild astigmatism or when exact cylinder correction is unnecessary.

What Does + or – Mean in My Prescription?

The plus (+) and minus (–) signs in the SPH (Sphere) column show the type of refractive error being corrected.

• A minus sign (–) indicates myopia (nearsightedness) — clear near vision but blurred distance. The lens corrects this by moving the focal point back onto the retina.
  

• A plus sign (+) indicates hyperopia (farsightedness) — clear distant vision but difficulty focusing on close objects. The lens adds power to shift the focal point forward onto the retina.

Both symbols are critical for ensuring lenses bend light precisely to match your eye’s focusing needs.