How to Read Your Prescription for Colored Contact Lenses
By Colored Contact Lenses Online | Seebelle | Published: 2026-10-13
Category: How-to Guides
Learn what each number on a colored contact lens prescription means, how it differs from your glasses prescription, and how to order the right power with confidence.
Quick answer
Read your contact lens prescription from left to right: power (sphere) tells you how strong each lens is, base curve (BC) tells you the curve that fits your eye, and diameter (DIA) tells you the lens width. If you have astigmatism, you will also see cylinder and axis values. Your glasses prescription is not a substitute for a contact lens prescription, because the two sit at different distances from your eye and are written in different formats. Before ordering prescription colored contacts, confirm that the base curve and diameter on the product match the values your eye care professional wrote for you.
Why your glasses prescription is not your contact lens prescription
A glasses prescription describes lenses that sit about 12 to 14 millimeters in front of your eye. A contact lens rests directly on the cornea, so the effective power changes. That is why an eye care professional may write a different sphere value for contacts than for glasses, especially at higher powers. Contact lens prescriptions also include base curve and diameter, which glasses prescriptions never contain. If you only have a glasses prescription, ask your eye care professional for a contact lens fitting and a separate contact lens prescription before buying prescription colored lenses online.
The numbers you will actually see on a colored contact lens prescription
Most prescriptions list power, base curve, and diameter. If you have astigmatism, you will also see cylinder and axis. Some prescriptions include a brand or material recommendation, and an expiration date. The expiration date matters because contact lens prescriptions typically expire after one to two years, depending on your eye care professional and your eye health. An expired prescription is not a valid basis for ordering, even if your vision has not noticeably changed.
- Power (sphere): the strength of the lens, written as a positive or negative number. This is the value you match to the Power option when ordering.
- Base curve (BC): the inside curve of the lens, written in millimeters. It needs to match the product's base curve for a comfortable fit.
- Diameter (DIA): the overall width of the lens in millimeters. A larger diameter covers more of the eye and can change how a colored lens looks.
- Cylinder and axis: only present if you have astigmatism. Cylinder is the amount of correction, axis is the orientation in degrees.
- Expiration date: the date after which the prescription is no longer valid for ordering.
How sphere, cylinder, and axis work together
Sphere corrects nearsightedness or farsightedness. Cylinder corrects astigmatism, which is an irregular curve of the cornea. Axis tells the lens lab where to position that cylinder correction, measured in degrees from 1 to 180. If your prescription has a cylinder value but no axis, or an axis value but no cylinder, the prescription is incomplete and you should not order from it. Standard colored contact lenses usually correct only sphere. If you have astigmatism, you need toric lenses, and colored toric options are far more limited. Check with your eye care professional about whether a spherical colored lens is appropriate for you before assuming any colored lens will work.
Reading a prescription when the numbers are written differently
Prescriptions can be handwritten, printed, or sent as a digital file. Some use plus signs for farsighted values and minus signs for nearsighted values. Some list the right eye (OD) first and the left eye (OS) second. If the two eyes have different powers, you must order the correct power for each eye separately. Do not average them or order two identical boxes unless both eyes genuinely share the same power. If any field is blank or unclear, call the prescribing office rather than guessing. A wrong power is not just uncomfortable; it can cause headaches and eye strain.
Step-by-step: from prescription to order
- Find the power for each eye: Locate the sphere value for the right eye (OD) and the left eye (OS). Write them down separately. Common mistake: copying the glasses power instead of the contact lens power, which can be off by several steps at higher prescriptions. Checkpoint: if the two eyes have different powers, you need two different powers in your order. Match each power to the Power option on the product page.
- Check base curve and diameter against the product: Compare the BC and DIA on your prescription to the product specifications. For example, the OMG series lists BC 8.5mm and DIA 14.0mm, while the Supersize Brown lists BC 8.6mm and DIA 14.5mm. Common mistake: assuming all colored lenses fit the same. Checkpoint: if your prescribed BC or DIA does not match the product, do not order that lens. A mismatch in BC or DIA is a fit problem, not a color problem.
- Confirm cylinder and axis if you have astigmatism: If your prescription includes cylinder and axis, you need toric lenses. Standard spherical colored lenses will not correct astigmatism. Common mistake: ordering a spherical colored lens because the color is available and hoping the astigmatism will not matter. Checkpoint: ask your eye care professional whether a spherical lens is safe and comfortable for your eyes before substituting. No cylinder or axis on the product means it is not a toric lens.
- Note the expiration date and replacement schedule: Check that your prescription is still valid. Then match it to the lens replacement schedule, such as the 6-month schedule on the Supersize and OMG lenses. Common mistake: using an expired prescription because the numbers still look right. Checkpoint: set a reminder to reorder or replace according to the schedule, not when the lenses start to feel uncomfortable. An expired prescription is not a valid basis for ordering.
- Order the correct quantity for each eye: If your eyes have different powers, order one box per power. If they share the same power, one box may cover both eyes depending on the pack size. Common mistake: ordering two boxes of the same power when only one eye needs it. Checkpoint: read the pack quantity before checkout so you do not run out mid-cycle. Verify the cart matches your prescription before paying.
Prescription colored lenses you can match to your numbers
- Brown Supersize Prescription Colored Contact Lenses (6 Months): Brown Supersize Prescription Colored Contact Lenses (6 Months) have a DIA of 14.5mm, BC of 8.6mm, water content of 38%, and a 6-month replacement schedule. The 14.5mm diameter is larger than a standard lens, so check that your prescribed diameter and base curve are compatible before ordering. The 6-month replacement schedule means you replace each pair twice a year.
- Black OMG Prescription Colored Contact Lenses (6 Months): Black OMG Prescription Colored Contact Lenses (6 Months) have a DIA of 14.0mm, BC of 8.5mm, water content of 38%, and a 6-month replacement schedule. A 14.0mm diameter and 8.5mm base curve are common values, so this lens may match more prescriptions. The 6-month schedule keeps the cost per wear low if you wear them regularly.
- Gray OMG Prescription Colored Contact Lenses (6 Months): Gray OMG Prescription Colored Contact Lenses (6 Months) have a DIA of 14.0mm, BC of 8.5mm, water content of 38%, and a 6-month replacement schedule. Same fit specifications as the black OMG lens, so if one fits well the other likely will too. The gray color gives a softer, more natural look than black.
