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Contact Lens Base Curve – What Is & How Importance Is It?

Contact lenses are not one-size-fits-all. Having the right fit is essential for clear vision and long-term comfort and satisfaction with your lenses. A well-fitted lens covers the cornea properly and prevents dryness due to an exposed cornea. A proper fit ensures full coverage of the cornea, optimum edge alignment and adequate movement of the lens for tear exchange. The base curve is an important factor in determining what the optimum fit is for you. Today, we’ll be looking at what the base curve of your contact lens is and how a properly fitted contact lens impacts your overall comfort. 

Estimated reading time: 5 minutes

What Is The Base Curve On A Contact Lens?

contact lens base curve
What is contact lens base curve?

It is the curvature of the back surface of the lens. The base curve determines the type of fit the lens must have to match the natural curvature of your eye. It is usually characterized as steep, median, or flat, and calculated in millimeters.

Studies show that a single base curve of 8.4mm managed a “good or better” fit in approximately 90% of individuals, and base curves of 8.4mm and 8.6mm together encompassed 98% of individuals.

Do These Numbers Mean Anything?

Typical base curve values range between 8.0 and 10.0 mm. In some cases, it can be as flat as 7.0mm, especially if you have a rigid gas-permeable lens. The baseline is that a person with a higher base curve number has a flatter cornea compared to someone with a lower base curve number, which indicates a steeper cornea.

Contact lens base curve 8.6 vs 8.8
Contact lens base curve 8.6 vs 8.8

Example: Contact Lens Base Curve of 8.6 vs 8.8

A base curve of 8.6 mm of the radius is more curved, and therefore a tighter fit, compared to the 8.8 mm base curve. People who have steeper corneas require tighter fitting contacts.

  • If contact is too loose, it may be uncomfortable, fold, or come right out.
  • If it’s too tight it may be comfortable at first but later cause irritation.

Why Is Contact Lens Base Curve Important?

Everyone’s eyes have a slightly different curvature and shape on the front surface of the eye, the cornea. The base curve of the lens is the closest possible to matching that curvature.

Each manufacturer designs its lens differently so a base curve may match one cornea in a different way to the same base curve from another manufacturer. A wrongly fitting lens could make the lens a little uncomfortable after wearing it for a few hours. At the worst, it could cause significant scarring or even damage to the cornea.

Always wear the contact lens that your optometrist has spent their time and experience fit for you.

Does Contact Lens Base Curve Matter?

Ordering contact lenses with a base curve that is different from your prescription can damage your eyes and cause problems with vision. This is especially important for people who purchase cosmetic colored contact lenses, which are often of a standardized size.

Wearing poorly-fitting contact lenses can damage the eye and cause problems such as blurred vision, headaches, and eye strain. The diameter and base curve of a contact lens are two measurements that affect how well they fit your eye.

Read more: Will The Wrong Base Curve of Contact Lenses Cause Discomfort?

Anyone who wants to buy a contact lens should know the necessary parameters. The contact lens parameters can be found in the prescription written by an eye doctor and are different from your regular spectacle prescriptions. 

It is also good to take note of changes in your base curve and diameter whenever you’re getting a prescription for new contacts as these parameters often change with age.


Contact lenses have come a long way, and they remain an effective, almost invisible tool to good eyesight. Making sure that you have a pair of well-fitting contact lenses is important for your eye health and your safety as well. 

Ultimately, talk to your eye doctor about the best type of lenses for you. Get regular eye exams to keep your eyes healthy and make sure your prescription stays up to date. Check out our site for all your contact lens needs.

Do you know contact lens cleanliness also plays an important role in ensuring eye comfortability?

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