The optometrist who prescribes them performs a contact lens fit as part of the eye exam, to be sure they fit properly.
The eye bulges out a little in that spot due to the cornea, the clear part of the eye in front of the iris and pupil that does most of the focusing of the light that enters the eye. A contact lens is designed to fit over that shape.
Most contacts are made within a few variations in size and shape, so that one of the combinations of options is likely to fit most people. Think of it like having S, M, L, and XL shirts: one of the standard sizes is likely to fit most people.
A good fit is tight enough to stay in place well and not cause ulcers by moving around too much on the eye, and loose enough to let a little of your eyes’ tears underneath to lubricate and nourish the eye and to not damage it by digging in to the cornea. The doctor checks for these conditions during the fitting (as well as other factors like how likely you are to take care of them properly and what your use/lifestyle is, to recommend ones made of materials that are better for how you will use them).
Some people have corneas too oddly shaped to wear normal contacts. Keratoconus, for example, is a condition of the eye that causes the cornea to grow out into a cone shape instead of the normal sphere.
A nice normally rounded contact lens won’t stay put over a conical cornea; think of it like trying to balance a bowl on a traffic cone with highway traffic roaring by. So mild to moderate stage may wear special scleral contacts that are larger, covering some or most of the whites of the eye (called the sclera) as well as the cornea, in order to stay on and also to help constrict the abnormal growth of the cornea.
A place I worked along time ago a guy I worked with asked me to check his eye because he couldn’t see but knew his contact hadn’t fallen out. It slide all the into the side of his eye. I had to pull him into the bathroom so I could wash my hands, and then sucessfully realigned it for him. Freakiest thing I ever did.
A few other commenters have already remarked on the horror stories of contacts being trapped under the lids or at the side of the eyes and that the contacts are designed to center themselves on the cornea. I’d just like to add (as a regular contact wearer myself) that basically every time that you blink you are correcting the position of the lens and re-centering it. It’s partly just your natural blink and partly a learned but now autonomic blink.
Occasionally – especially if your eyes get too dry or too teary – your lens will drift off to one side and you’ll need to assist it back into place with your finger – if it persists take it out, rinse it in solution and put it back in after letting the eye calm down.
People already mentioned that it’s because your cornea sticks out, but I just wanted to say a fun fact, you can actually feel the cornea sticking out, just close one or both eyes, very gently put a finger over your closed eyelid so you’d be touching your eyeball through your eyelid, and move your closed eye side to side so the cornea moves around (look side to side, as in move your eyeball), and you’ll be able to feel it with your finger through your eyelid. It’s pretty interesting.
Latest Answers