My brother’s away at college. His contacts feel fine, and I see great in them. I can easily order new ones online. What’s wrong with that?
Well, Lil’ Bro, what if the power is wrong?
Your vision will either blur and/or fatigue. Although uncomfortable, neither causes death, illness or blindness. If the powers are exactly correct … well then, it’s okay. That likelihood is remote, but so far so good.
Now let’s address physical fitting aspects of a contact lens. If they fit too loosely, you would not have said, “His contacts feel fine…,” because loose contacts are uncomfortable.
If they are too tight, they feel great for a while, maybe even for several weeks or months, but the cornea suffers from insufficient tear exchange and hypoxia. Inflammatory disease ensues.
Insufficient tear exchange means not enough moisture or nutrients. The tears also contain lysozyme which keeps bacteria and other “bugs” from attacking the ocular surface.
The cornea, being avascular, depends on the air in front of it for oxygen. Hypoxic means insufficient oxygen, and the cornea takes on more water both inside and between cells, i.e. it becomes edematous which makes the tissue boggy and foggy.
The cornea also summons help from the surrounding tissues. The thin clear tissue overlying the rest of the eye adjacent to the cornea is the conjunctiva. It senses corneal distress. The conjunctiva, getting its nutrition from the blood, begins delivering new blood vessels to its neighbor, the edematous cornea. Although neighborly, it’s a bad idea! This inflammatory process is called pannus, which not only means unwanted vessels but fibrous tissue causing more clouding all of which, if it extends over the pupil, impairs vision.
This compromised inflamed tissue with inadequate lysozyme is susceptible to bacteria, viruses, fungi and parasites. When these organisms concentrate and eat away tissue, a corneal ulcer is formed. If an ulcer lies over the pupil it reduces vision. Ulcers scar, so the impairment is permanent. Even if the ulcer is way peripheral it hurts like crazy. If left untreated, the organism eats clean through the cornea. That’s called a perforating ulcer. Now you got some real problems.
Will any of this happen to you? Who knows? It’s kinda like asking, “If I drink and drive will I have an accident?” Actually the percentages are on your side. So it is with wearing your brother’s contact lenses. Like drinking and driving, if you can get by with it, does that make it a good idea? But, unlike drinking and driving the only victim is you!
Photo credit: By James Heilman, MD (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons