1.Overview
Small foreign body debris resting on the corneal surface or stabbed into the cornea is called corneal foreign body, the most common for the machine tool spattered metal shavings, knocking up the tiny fragments, the explosion of metal or gunpowder particles, coal chips, stone chips, flying with the wind dust particles, grain shells, fine thorns and so on. Corneal foreign bodies are most prevalent in factory workers with iron filings. Most of the corneal foreign bodies are found in the superficial branches or surface of the cornea, but there are also those that penetrate into the deeper layers of the cornea. As for the number of foreign bodies, it can be one, several or many for several days.
2.Clinical manifestations
Due to the exposure of sensory nerve endings, the patient suddenly experiences obvious pain, lacrimation, eyelid spasm and other irritation symptoms, and the pain increases when the eye is transient or the eye is turned. Even if no foreign body is present, the patient still has a distinct foreign body sensation.
Because the surface layer of the cornea is rich in sensory nerve endings and is extremely sensitive to pain and touch, corneal foreign bodies immediately cause obvious irritation symptoms, such as foreign body sensation, stinging pain, tearing, conjunctival congestion, and eyelid cramps. The irritation symptoms of superficial foreign bodies are often more pronounced than those of deeper layers.
Foreign bodies containing iron often cause corneal infiltration, and brown rusty rings may appear around them after 1 to 2 days of foreign body retention. Burning foreign bodies can cause burns to the surrounding corneal tissue or the formation of charcoal rings. If the foreign body causes infection, it can lead to corneal ulceration.
3.Auxiliary examination
Inspection seen: some corneal foreign body is obvious and easy to see, with the focal light oblique illumination method can see the location of the foreign body; some are not easy to find, must be examined by slit lamp, especially small and transparent foreign body, must be carefully searched before, if necessary, can be dropped with fluorescein, the foreign body around the cornea coloring and make the foreign body easy to find. During the examination, we should pay attention to the depth of the location of the foreign body, the deeper foreign body can be partially into the anterior chamber. Some corneal foreign bodies, especially those caused by explosion injuries, can often appear within 24 to 48 hours after the injury, traumatic corneal endothelial necrosis, but disappear after a few days.
The corneal epithelial defect can be found by oblique illumination with focal light (e.g., flashlight light source, etc.). At the same time, attention should be paid to the presence of corneal or conjunctival foreign bodies. In particular, the aforementioned conjunctival foreign body not only has similar symptoms to corneal abrasions, and is often the cause of corneal abrasions, if the epithelial defect is not found by oblique light method, then fluorescein staining method can be used. The method is to use a drop of 20% sodium fluorescein sterile solution into the conjunctival sac, ask the patient to close the eyes for 5 minutes, and then pause for a moment, then the patient’s tears can be washed away the remaining dye in the conjunctival sac (if there is still more dye, saline rinse can be used to remove it), at this time, because the corneal epithelial defect is stained green and easy to find. In addition, because the aqueous solution of fluorescein is a good culture medium for Pseudomonas aeruginosa, it is easy to be contaminated by such bacteria, resulting in serious infection of the corneal wound. Therefore, more recently, fluorescein paper staining is used, i.e., a strip of sterile fluorescein paper with a drop of sterile saline, so that one end touches the lid conjunctiva. In addition, if fluorescein is not used, small, inconspicuous abrasions can be examined with the help of projection. When the cornea is illuminated with a well-focused light source, a projection of the epithelial defect is seen on the iris surface, with a corresponding reverse movement of the projection when the angle of illumination is changed. If the patient is exposed to the examination in a hospital with ophthalmic equipment, it is of course more convenient to examine with a slit class microscope.
4.Treatment measures
After examination and discovery of corneal foreign body, it should be removed as soon as possible, by.
(1) attached to the corneal surface of the foreign body, can be removed by flushing method, that is, the water flow when flushing with the eye wash pot or rinse, rushing to the bulbar conjunctiva close to the foreign body, then the foreign body can be washed away, this method, corneal damage is minimal.
(2) Although the foreign body is on the surface of the cornea, but the rinse method can not be removed, then 1 to 2 drops of surface anesthetics, such as 1% of cocaine solution, wet cotton swabs dipped in saline, the foreign body will be gently wiped away.
(3) embedded in the corneal superficial foreign body, such as the end of the corneal surface, can also be tried according to the above method, with a wet cotton swab to wipe away.
(4) If the foreign body is not exposed to the corneal surface, or is exposed but firmly embedded, and cannot be removed by the above methods, it can be removed by a foreign body needle or fine injection needle under surface anesthesia, and the tip of the needle should face the direction of the head when picking the foreign body to prevent the patient from avoiding or suddenly closing the eyeball when the eye turns up and the tip of the needle is pierced too deep.
(5) If the foreign body is located in the deep layer, such as magnetic, the shallow cornea can be cut open to reach the foreign body, and then it can be sucked out by electromagnet or constant magnet; if it is non-magnetic or magnetic foreign body that cannot be sucked out by magnet, a small corneal flap must be cut first to separate the layers, lift this flap to reveal the foreign body and carefully remove it, because the corneal flap is small, it can be left unsutured, and after resetting the corneal flap, the affected eye should be bandaged with pressure, and both eyes should be bandaged 24 to 48 hours. The corneal flap can also be closed with a non-invasive corneal needle and 10-0 suture. The deep corneal foreign body should be handled with extreme caution, otherwise the foreign body may be pushed deeper when removed, so that it may penetrate the cornea and fall into the anterior chamber; or the anterior chamber may become shallow or disappear due to atrial water flow, and the foreign body or instrument may injure the iris or crystal.
(6) If one end of the foreign body has already entered the anterior chamber, the pupil should first be constricted and then the cornea should be cut from the edge of the cornea, and the iris restorer should be inserted into the anterior chamber to hold the foreign body behind the cornea and then remove it from outside the cornea, or a corneal flap should be cut as described above and the foreign body removed from under the flap. The foreign body can also be removed by intentionally dropping it into the anterior chamber to the surface of the iris after pupil reduction, and then removing it by pressing the anterior chamber foreign body.
(7) If the foreign body is a numerous debris or dust-like foreign body for several days, the larger particles that are exposed to the surface can be removed. Later, as the foreign body gradually moves forward to the surface, then one after another will be exposed to remove. If the debris is extremely large and the irritation is severe, lamellar corneal transplantation or epithelial scraping can be performed to remove the superficial foreign body together.
(8) Removal of the foreign body must be performed under good lighting conditions. Smaller foreign bodies should be operated with binocular magnification. Very small foreign bodies are best treated under a slit lamp or operating microscope. Deep foreign bodies, especially those requiring a corneal flap, should be operated on under an operating microscope with a slit light source.
(9) The rusty ring can be scraped off with a foreign body needle or sterile needle immediately after the foreign body is removed. If scraping is done after several days, it will be easier to scrape off. The chemical method to remove the rust ring is to apply the chelating agent deforoxamine locally, using a 5% to 10% solution or eye ointment, 4 to 6 times a day, which can be used for those who have not scraped the rust ring clean. Carbon rings are easier to remove, sometimes with a fine needle can be removed once the complete, can also be used to scrape the foreign body needle.
(10) Precautions: The removal of the foreign body should be done with extreme accuracy to minimize corneal damage. The aseptic requirements should be strictly observed. The instruments and all drugs used, including fluorescein, cocaine, saline, antibiotic ointment or eye drops, should be kept sterile. The commonly available drugs should be replaced regularly to avoid infection, especially Pseudomonas aeruginosa infection, which should be given more attention.
(11) Post-therapy: After foreign body removal, apply antibiotic eye ointment and cover the single eye with sterile gauze against pressure bandage. Exchange dressings daily until healed. General foreign body removal, the wound is very small, the corneal epithelium can be repaired within 24 hours. Larger and deeper wound surface, such as infection has occurred, then according to the corneal ulcer treatment.
(12) corneal foreign body shallow, after the removal of foreign body, more do not remain obvious corneal clouding, but individual can occur corneal white spots. Foreign body deeper, although timely removal of foreign bodies, but also often left behind a certain amount of corneal clouding. This clouding, if located in the pupil area, will seriously affect vision, that is, or not located in the central part of the cornea, but also due to the contraction of the scar and cause corneal refractive error, such as astigmatism, can also cause vision loss.