Contact Lens Base Curve & Diameter Explained (and why they are so important)

The base curve and diameter of contact lenses are two important factors to consider when purchasing lenses. The base curve refers to the curvature of the back surface of the lens, while the diameter is the width of the lens. These measurements are crucial for ensuring the contact lenses' comfortable and safe fit on the wearer's eyes.

What is the base curve of a contact lens?

The base curve of a contact lens is measured in millimeters and is specific to each individual's eye shape. While base curves come in a range of different sizes, they typically fall between 8 and 10 millimetres. The higher your base curve measurement, the flatter your cornea whereas a lower base curve reading reveals a steeper cornea. It is important to get the right base curve for your contact lenses because a lens with a poor fit can cause irritation and a lens with the wrong base curve may not provide optimal vision correction. Your optometrist can help you determine the correct base curve for your contact lenses.

What is the diameter of a contact lens?

The diameter of a contact lens is the width of the lens from edge to edge and is determined by the size of the wearer's iris. Also measured in millimeters, a typical contact lens diameter usually falls between 13 and 15 millimeters. As with the base curve, It is important to get the right diameter for your contact lenses to ensure a comfortable and effective fit. A contact lens with the wrong diameter can cause discomfort and redness, as well as difficulty seeing.

The impact of using contact lenses with the wrong diameter and base curve:

Unfortunately, contact lenses are not “one size for all” and you must ensure that your lenses are the correct fit for your eyes. Wearing contact lenses that are not the correct size can have several negative effects. Some of the potential impacts of wearing lenses with the wrong base curve or diameter include the following:

• Discomfort and irritation: Contact lenses that do not fit properly can cause discomfort and irritation, such as redness and itching.
  
• Blurred vision: Poorly fitting contact lenses can affect your vision, leading to blurry or distorted vision.
• Dry eye: A lens that does not fit properly can cause dryness of the eye, leading to discomfort and potential damage to the eye.
  
• Eye strain: Wearing contact lenses that do not fit well can cause eye strain, leading to headaches and other symptoms.
  
• Risk of eye damage: Wearing contact lenses that do not fit properly can increase the risk of eye damage, such as corneal abrasion or infection.
  

Overall, it is important to choose contact lenses with the correct base curve and diameter in order to avoid these negative effects and ensure a comfortable and effective fit.

When ordering your contact lenses online, ensure that you select the correct base curve and diameter based on your prescription from your optometrist.