Familiarity with how to read prescription for contacts is highly essential. It is because, without proper knowledge of prescription metrics, you will probably end up with a box of lenses that do not fit your eye or help you see clearly.
To help you out, we have created a handy guide that can help you understand everything from minimal to the most relevant details given on the contact lens prescription.
Let’s begin with knowing where you find prescription details and then move further in comprehending the supreme components of your contact lens prescription slip.
Where To Look For Reading Prescription?
You can find the details about the contact lenses that you should wear on:
- the lens prescription provided by your optician.
- the side of the box of contact lens.
But, in case you cannot locate it on the prescription slip, you can also contact your optician to get the details of the contact lenses you need to wear.
How To Read Contact Lens Prescription By Unraveling Symbols And Figures?
While learning how to read contact prescription on box, you will generally come across the following symbols and figures. These are:
- OD- For the right eye
- OS – For left eye
- OU – For both eyes
- SPH – Sphere, commonly known as Power or PWR
- BC – Base Curve
- DIA – Diameter
- CYL- Cylinder
- Brand – The brand of lens that your doctor recommended you.
Let’s untangle the above components one by one and recognize the complete meaning of the prescription.
OD, OS, And OU
On the top of any prescription slip or the contact box, you will notice the letters OD and OS.
OD is a short form of the Latin word ‘Oculus Dexter, which is about the Right eye. And short-form OD comes from the Latin word ‘Oculus Sinister, which is for the Left eye.
Sometimes, you may find the letters OU on your prescription slip, which is a short form for ‘Oculus Torque’ or Both eyes, which implies the equal measurement applies to both eyes.
Power (PWR) / Sphere (SPH)
This number indicates the lens power you need to correct your farsightedness and nearsightedness. Measured in Dioptres (D), this measurement unit brings your vision to 20/20 or as close as possible.
A minus sign (-) of this value indicates that you are near-sighted or have Myopia. And a plus (+) sign indicates that you are far-sighted or have Hyperopia. The more the number is from zero, the stronger your prescription is. Remember, you may have this value different for both eyes.
Base Curve (BC)
Base Curve is the number that indicates how curved or concave your contact lenses are. This number helps your optician match the curve of the contact lens to the curve of the eye so that you will get the best-fitted contact lens for you.
The base curve number ranges between 8 millimeters to 10 millimeters. If your slip does not comprise a base curve, it is likely due to the brand of your lenses available only in one base curve.
Diameter (DIA)
Diameter is the total distance from the edge of the contact lens to the edge of the other contact lens. The value of diameter occurs to be between 13 millimeters to 15 millimeters.
Diameter helps in determining where the contact lens will settle on your eye. If this length is not correct, the contact lens will be painful and may scrape your eye.
Contact Lens’ Brand
Almost all contact lens prescription slips will have a manufacturer or brand name. That is very helpful to you in the case of reordering lenses.
The popular manufacturers or brands you will encounter in the market are ACUVUE, Ciba Vision, CooperVision, and Bausch & Lomb.
Deciphering A Lens Equation
Sometimes, contact lens prescriptions can be in equation form. So, it will usually follow this order:
+/- SPH/Power +/- CYL x Axis, Base Curve ‘BC’= diameter DIA = Number.
For example +2.25-1.50×110, BC=8.8 DIA=14.0.
In this case, if you are unsure about how to read prescription on contacts that is the lens equation, you can consult your doctor for its interpretation.
Following are the other components that form your lens equation:
Cylinder (CYL)
This value shows the amount of astigmatism you have and how curved your eye layouts are. If the value is empty, that means you do not have astigmatism and have only short-sightedness.
But when the value is between -4 and +4, that implies you have astigmatism and need lenses to correct it.
Axis Value
Axis is extra power added to your contact lenses to correct astigmatism. The doctors calculated it in degrees. And its value varies between 0° and 180°.
Additional Power (ADD)
ADD is the magnifying power added to the multifocal contact lens. This value helps you in seeing close and doing reading tasks.
The ADD value can be written as Low, High, Medium, and is always a positive number, for example, High+0.75.
Additional Contact Lens Prescription Notes
The contact lens prescriptions are not the same as eyeglass prescriptions. So when you learn how to read eye prescription for contacts, you may find many pieces of information associated with the lens size. These will include:
Contact Lens Expiration Date
The expiration of the contact lens usually comprises one year from the date when the contact lenses were placed.
Color Lenses
This part of the prescription is pretty self-explanatory. Your contact lenses have different colors(red, blue, green) or designs like a spiral or cat-eye.
There are two types of color contacts that your optician will give you. The Enhancing color contacts do a subtle variation to your eyes. And Opaque color contacts completely change the color of your eyes.
In some cases, your prescription slip may also include how often you need to replace the lens daily, weekly, monthly, etc.
Are Contact Lens Prescriptions And Glass Prescriptions The Same?
Prescriptions for contact lenses are not the same as prescriptions for eyeglasses. Yet, it is common to get confused between lens prescriptions. So, it is essential to understand the difference between the two while buying contact lenses.
Major differences between contact lens prescriptions and glasses prescriptions.
- The first difference is that you cannot use prescription glasses to buy contact lenses. It is because a contact lens settles on the surface of the eye. But an eyeglass lens fits a little further away. This distinction in location influences the resulting ability of the lens.
- The second difference is that the values of the sphere, axis, and cylinder found in an eyeglasses prescription need to be modified by your optician to get similar power in a contact lens. And this is something that your optician can compute only for you.
- The third difference is that an eyeglasses prescription will not include base curves, diameter, and the brand name of the contact lens. Likewise, a contact lens prescription will generally not include an axis value.
Summing Up
Hope you got your answer to how to read prescription for contacts. The right approach will work as a golden ticket to clear vision and freedom from glasses. We hope this article vanishes any contradiction surrounding your contact lens prescription.
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