Reader Question: When It Comes to Contacts, Does One Size Fit All?


Reader Question:

Recently, a friend tore her contact lens while at my house when we were getting ready to go somewhere, and she didn’t have her glasses along. She happened to know her contact lens prescription, and it was the same as mine. I had a new lens still in the package (I know enough not to share lenses), so I gave it to her. Was this okay? As long as we wear the same prescription, wouldn’t our contact lenses be the same?

Thanks for your help,

Linda in Atlanta


Dear Linda:

It was mighty generous of you to help your friend out by offering a brand new lens. I’m so glad that you clarified that the lens was new and still in its packaging. So many people don’t realize how unsafe it is to share contact lenses – even those that have been sterilized – so I appreciate your making the distinction.

While it’s not altogether unsafe that you gave a friend a brand new contact lens to use, it is important to note that not all contact lenses are created equally, even if they are the same basic prescription.

In fact, contact lens prescriptions are comprised of more than just the strength of the lens, or what is called the diopter. The diopter, or power, of the lens is that number that says -2.50 or +1.50, etc… But your contact lens prescription also contains a lens size, or the base curve. This is the measurement of the back of the lens diameter. An average base curve size is somewhere between 8.0 and 10.0. This is yet another number you’ll see in your contact lens prescription.

The final measurement that is involved in properly fitting a contact lens is the diameter, or size, of the actual contact. This number is usually a measurement in millimeters.

There’s a good chance that you and your friend’s measurements were close enough to where she may not have noticed any difference in wearing your new lens for day or two. But, ideally, it would be best for her to stick with the size that her own optometrist prescribed to her for any additional use.

Contact lenses need to fit correctly in order to work optimally. And a lens that is too small or too large may not sit well on the eye ball. It could shift around a lot or just be less comfortable than her usual lens size, or it could cause bigger issues over time.

Be sure to talk to your optometrist at your closest America’s Best store to find out even more about the importance of wearing properly sized contact lenses.

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