When a metallic foreign body strikes the cornea or clear surface of the eyeball over the iris and pupil, it generally sticks to that structure. Because the surface of the eyeball is generally wet, the metallic foreign body begins to rust quickly. The removal of a corneal rust ring is necessary. If the rust ring is left in the cornea, it will result in recurrent corneal erosion. This is a painful condition where the cornea will become scratched at random times as the rust moves through the cells on the top of the cornea.
Instil one drop of a topical anesthetic such as proparacaine 0.5-per cent ophthalmic solution into the affected eye. Wait at least 20 seconds before attempting to make physical contact with the eyeball.
Insert the eyelid speculum by gently affixing it to the upper eyelid and then to the lower eyelid. This works as an eyelid clamp to prevent the patient from blinking his eyes during the procedure.
Position the patient in the slit lamp microscope. Ensure that his chin is in the chin rest and his head is against the head rest. Provide a fixation target for his opposite eye that positions his affected eye in the slit lamp microscope's light beam.
Use a properly sterilised Alger Brush to remove the rust ring. Position the patient in the slit lamp microscope where his chin is positioned in the chin rest and his head is firmly against the head rest. Ensure that he is seated comfortably. Provide a fixation target for his opposite eye that moves his affected eye into a position where the rust ring can be easily accessed. Manually spin the tip of the Alger Brush to begin its rotation. It will continue spinning until it comes into contact with a surface that is dense enough to cause it to stop. Bring the spinning Alger Brush toward the cornea so that it is tangential with the surface of the eye. Make light contact with the tip of the Alger Brush to the area of the rust ring. Continue this process until the no further rust is visible on the cornea. If the Alger Brush begins to go too far into the cornea, it will stop automatically.
Use a sterile cotton tipped applicator to remove any dead corneal cells from the area of rust ring removal. These will appear as grey mounds of tissue in the slit lamp microscope. Gently wipe them away in a direction away from the pupil.
This procedure is unpleasant for the patient. Gently remind him that he must maintain fixation on the target that was provided for him. Also, some patients may become nauseated or feint during this procedure. Constantly reassure the patient and ask if he is feeling well.
This procedure can result in permanent eye damage and vision loss if it is performed improperly. It can only be performed by a licensed health care professional such as an ophthalmologist of optometrist. Do not attempt this procedure if you do not carry these credentials. Doing so is illegal, and it could put someone's vision at serious risk.