Understanding Vision Values and How to Read Your Eye Prescription

Reading Eye Prescription Values: An Easy-to-Understand Guide

Reading an eye prescription may seem complicated to many because the slip often contains numerous numbers and symbols. However, understanding your own eye prescription is essential because it helps us choose the appropriate eyeglasses or contact lenses for our vision, resulting in clearer and more comfortable vision. This article will introduce you to eye prescription values and an easy way to read them on your prescription slip, so you can understand your eye health better.

What is Vision Prescription Value?

The vision prescription value is a measurement that indicates how clearly we can see and what problems exist with our vision, such as nearsightedness (myopia), farsightedness (hyperopia), or astigmatism. The value is expressed in diopters (D) and may be preceded by a plus (+) or minus (-) sign.

When we undergo an eye examination, we receive an eye prescription slip detailing the results, which is used to address vision problems, such as ordering suitable eyeglasses or contact lenses, to help us see more sharply.

What are the Types of Vision Problems?

• Nearsightedness (Myopia) is a condition where distant objects are blurry, but near objects are seen clearly. It is often found in students or working adults under the age of 40.
• Farsightedness (Hyperopia) is a condition where distant objects are seen clearly, but there is difficulty seeing at close range. This includes congenital farsightedness, general farsightedness, and age-related farsightedness (presbyopia).
• Astigmatism is a condition where vision is distorted or not sharp. This condition can occur together with nearsightedness or farsightedness and must be corrected with specially designed lenses.

Are the Right and Left Eye Prescriptions Different?

In principle, the two eyes of a person may have different prescription values. On the prescription slip, this is often indicated by the symbols OD (Oculus Dexter) for the right eye (some places may use the abbreviation RE) and OS (Oculus Sinister) for the left eye (some places may use the abbreviation LE).

A difference in prescription values between the two eyes is normal. Therefore, it is necessary to measure and read the prescription for each eye separately and thoroughly to get lenses that are suitable for each eye.

What Does an Eye Prescription Slip Consist Of?

When you have your eyes examined, you will receive a prescription slip that specifies various values essential for making eyeglasses or contact lenses. Let's get to know the important components of an eye prescription slip.

1. Sphere (SPH)

Sphere or SPH is the value that indicates the amount of lens power needed to correct basic vision problems. If the SPH value has a minus sign (-), it indicates nearsightedness (e.g., -2.50 D means 250 degrees of nearsightedness). A plus sign (+) indicates farsightedness (e.g., +1.75 D means 175 degrees of farsightedness). The SPH value is the main indicator that determines the thickness and weight of the eyeglass lens.

2. Cylinder (CYL)

Cylinder or CYL is the value that indicates the severity of astigmatism. The number in the CYL box is always located after the SPH value and before the Axis value. It is often expressed with a minus sign (-). The greater the value, the more severe the astigmatism (e.g., CYL -1.25 means 125 degrees of astigmatism).

3. Axis

Axis specifies the orientation of the astigmatism in degrees, ranging from 1 to 180 degrees. If the prescription slip has an astigmatism value (CYL), it must always have an astigmatism axis value (Axis) as well.

4. Add

The Add value indicates the additional magnifying power for correcting age-related farsightedness (presbyopia), which is added to the lower part of the lens. The Add value ranges from +0.75 up to +3.00 diopters. Lenses with an Add value are often bifocal or progressive lenses.

5. Prism

Prism or PH is a special value used to correct conditions like strabismus (squint) or weak eye muscles. Special lenses with an added Prism value help adjust the line of sight so that both eyes can work together better, helping to normalize the visual alignment.

6. Other Units That May Be Found Additionally

In addition to the basic values mentioned, when reading an eye prescription slip, you might encounter other values:

• PD (Pupillary Distance) indicates the distance between the centers of the pupils of both eyes.
• NPD (Interpupillary Distance at near) is the distance between the centers of both eyes when looking at close range.
• VD (Cornea Vertex Distance) indicates the distance between the cornea and the eyeglass lens.
• SE (Spherical Equivalent) is a value obtained by calculating the sum of the sphere (nearsightedness or farsightedness) and cylinder (astigmatism) values.

Easy Way to Read Eye Prescription

Reading an eye prescription is not as difficult as it seems if you understand the meaning of each part.

Example: Suppose your eye prescription slip says:

The way to read the values from this slip starts with:

Right Eye (OD)

• Has nearsightedness of 175 degrees (SPH -1.75)
• Has astigmatism of 50 degrees (CYL -0.55), with the astigmatism problem being in the vertical axis of the eye (Axis 95 degrees).
• Requires additional lens power of +2.00 (ADD).

Left Eye (OS)

• Has nearsightedness of 200 degrees (SPH -2.00).
• No astigmatism, as there are no CYL and Axis values.
• Requires additional lens power of +2.00 (ADD).

Eyeglass Prescription vs. Contact Lens Prescription Are Not the Same

The prescription values for eyeglasses and contact lenses differ due to the unequal distance between the lens and the eye. Contact lenses sit directly on the cornea, while eyeglasses are spaced away from the cornea. This means the prescription values must be adjusted to suit each type of device, especially for people with high prescription values or significant astigmatism. Therefore, you should not use an eyeglass prescription to order contact lenses without a proper measurement.

Article Summary

Understanding eye prescription values and how to read them is a fundamental step in taking care of your eye health. The various values that appear on the prescription slip—whether SPH, CYL, Axis, or other additional values—are all important in determining the appropriate lenses for each individual's vision condition.

Regular eye examinations and choosing the right vision aids will help prevent eye problems from becoming more severe in the future. If you notice any visual abnormalities, you can consult with experts and optometrists at ISOPTIK Progressive Eyeglasses Center. We have a team of expert optometrists and ophthalmologists ready to provide consultation, design, and thoroughly analyze your vision use, with Master Bobi closely supervising every step, so you receive comfortable progressive eyeglasses that meet your needs and help elevate your quality of life, along with a maximum satisfaction guarantee of 180 days.

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