You might have noticed numbers on your contact lenses before, but do you know why they are there, and what you can use them for?
See if your contact lens is oriented correctly
The purpose of the 123 inside your contact lenses is that you can easily see if they are oriented correctly. In other words, whether they are facing inwards or outwards.
If you can see 123 when you look at your contact lenses, then you know they are oriented correctly. If 123 is mirrored, then your contact lenses are oriented incorrectly, and you need to flip them.
Can I see the numbers when I am wearing contact lenses?
Don't worry, you can't see 123 when you are using your contact lenses. The marking is just made so you can see if your contact lenses are oriented correctly. It doesn't make a difference to your vision in the end. Other than of course, you can be sure that your contact lenses are correctly oriented.
Does it say 123 in all contact lenses?
It is only Acuvue contact lenses that have 123 inscribed inside. So if you use contact lenses from another brand, there will not be 123 in your contact lenses.
It's not every Acuvue contact lens that uses the 123 inside-outside marking, but the vast majority do.