The cornea is a clear dome of skin covering the pupil, where light shines into the eye so we can see; it’s where people place contact lenses (see diagram Eye — Anatomy). It’s full of nerves, so even the least little “abrasion” (scratch) hurts like crazy. As opposed to Conjunctivitis, conditions of the cornea are truly painful.
Sometimes we can see the abrasion by looking carefully at the cornea, perhaps with the magnifying capacity of an ophthalmoscope (most commonly used to see back behind the pupil, but can also be used for the outer eye). However, we usually have to stain the cornea with fluorescein, which seeps into the abrasion, and then shine an ultraviolet light to make the stain bright orange. Most primary care settings have these, certainly urgent cares.
Corneal abrasions heal very rapidly, within 24 hours. In the meantime, pain medicines help, as strong as necessary (even a few doses of narcotics). We used to place patches with light pressure, but studies show they interfere with healing. We refer to an ophthalmologist if pain is not completely gone in 24 hours, to be sure there’s no complication.
We also refer to an ophthalmologist if we suspect the pain may be deeper than the cornea. One way to tell is to put a drop of local anesthetic in the eye. completely relieving eye pain from corneal disease. If it doesn’t work, it’s not the cornea that’s involved (or not only the cornea). However, we warn the patient that with the anesthetic, pain will be completely relieved, but only for 5 minutes. We’re using the drops diagnostically, and will NOT give the patient a prescription, because repeated use can destroy the cornea.
Another sign of deeper, more serious eye injury is “cross-photophobia” — shining a bright light in the good eye makes the bad (injured) eye hurt! If there’s a corneal abrasion, shining a light in the bad eye itself may cause painful glare. But we know that when light hits one eye, both pupils constrict. The only ocular structure which does anything when light shines in the other eye is the Iris, which manipulates the pupil. So if bright light in the good eye causes pain on the other, we know that injury is deeper than just the cornea
I’ve seen patients with pain from having “scratched the eye.” On further questioning, I found that the “scratch” happened last week, the pain began last night. Corneal abrasions hurt from the exact moment of injury; these 2 patients had sight-threatening corneal ulcers, which are bacterial infections. It may be natural to try to figure out why something hurts you, but please don’t convince yourself; allow your provider to doubt your ideas and use their professional training to figure out the real cause.
The annual risk of corneal ulcers from extended-wear contact lenses is 1 in 1,000, which equals 1 in 20 over 50 years. Any wearer with eye pain should remove the lens immediately. If the pain hasn’t gone away in 1-2 hours, they should see an eye specialist. It may just be an abrasion, but could be much worse.
Corneal Foreign Body
A “foreign body” means anything that doesn’t belong in the eye, like specks of dirt, a loose eyelash, etc. Nothing to do with nationality nor sensuality. Foreign bodies on the cornea by definition cause abrasions, so they hurt. We can usually see them without the need for fluorescein staining (see above). We can try to remove them with a Q-tip (after putting a drop of short-acting anesthetic in the eye first), but shouldn’t try too hard, since that might cause more abrasions. Usually these have to be removed by an eye specialist or in an E.R., where they have slit lamp equipment.
By the way, if someone happened to get a weird sense of “something in my eye” while working in a metal shop, or any place people were cutting or hammering steel, it’s possible that a tiny piece of metal penetrated the eyeball, which rapidly sealed itself. The symptom may have completely disappeared, but the fact that it was felt in such a setting requires a referral to an Ophthalmologist, even if no treatment winds up necessary.
People can live & see just fine with tiny pieces of metal deep in their eyes. But if they ever get an MRI for any reason, the magnet will whip that tiny unnoticed piece of metal back & forth [yuck!]. MRI techs always ask about the possibility first; I’ve always wondered if that got thought out ahead of time, or if it took a couple of bad outcomes to raise the query.
Recurrent Corneal Abrasions
For some patients with corneal abrasions, healing is incomplete. So a new abrasion can occur again on its own in the future, without any trauma. Since there’s no history of repeat injury, the condition may resemble a sight-threatening infection. We send such patients straight to an ophthalmologist, best via an E.R.
Recurrent corneal abrasions are difficult to manage, since the cornea never healed in the first place. Ophthalmologists have a variety of techniques to try.