2023-04-21 01:53:00
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the anterior chamber and the lens, it refracts light and is responsible for two-thirds of the eye’s total power and helps protect the eye from germs, dust, and other harmful materials. In humans, the refractive power of the cornea is approximately 43 diopters.
Corneal diseases are varied and can cause pain and vision loss. Among them we can find refractive errors, allergies, infections, injuries, dystrophies (condition in which some parts of the cornea lose transparency due to the accumulation of cloudy material). Treatment of corneal diseases includes medicines, transplantation, and laser surgery.
Superficial punctate keratitis
This disease consists of the cells on the surface of the cornea dying due to a viral or bacterial infection, dry eyes, exposure to UV rays (sunlight, sunlamps or welding arcs), irritation from the use prolonged use of contact lenses or an allergic reaction. It can also be the side effect of taking vidarabine.
There is pain in the eyes, which become watery, sensitive to light and bloodshot, and vision may be slightly blurred. When ultraviolet rays cause this disease, symptoms usually do not appear for several hours and last a few days. When a virus causes this process, the lymph node in front of the ear may be swollen and painful.
Almost all people who suffer from this disease recover completely. When the cause is a virus, no treatment is needed and recovery is usually complete within 3 weeks. When the cause is a bacterial infection, antibiotics are used and when it is due to dry eyes or UV rays, a treatment with ointments and artificial tears is applied.
Corneal ulcer (corneal ulcer)
This condition is a perforation of the cornea, usually due to an infection caused by bacteria, fungi, viruses or Acanthamoeba. Other times, it is the result of an injury. When the eyelids do not close properly to protect the eye and moisten the cornea, ulcers can develop due to dryness and irritation.
Bacteria (usually staphylococci) can infect and ulcerate the cornea when the eye has been injured, a foreign body has entered it, or is irritated by contact lenses. Fungus can cause slow-growing ulcers. Very rarely, vitamin A or protein deficiency can cause corneal ulceration.
UC causes pain, sensitivity to light and increased tear secretion. A yellowish white spot of pus may appear. In certain cases, ulcers appear over the entire cornea and can penetrate deeply and a certain amount of pus can also accumulate behind the cornea. The deeper the ulcer, the more severe the symptoms and complications.
Corneal ulcers can close with treatment, but they can leave behind cloudy, fibrous material that causes scarring and impairs vision. Other complications include persistent infections, perforation of the cornea, displacement of the iris, and destruction of the eye.
herpes simplex infection
The initial manifestation of corneal herpes infection may appear to be a mild bacterial infection because the eyes are slightly sore, watery, red, and sensitive to light. Inflammation of the cornea clouds vision. However, herpes infection does not respond to antibiotics, as a bacterial infection would, and often gets worse and worse.
Most often, the infection causes only slight changes to the cornea and goes away without treatment. In very rare cases, the virus penetrates deep into the cornea, destroying its surface. The infection may recur, further damaging the surface of the cornea. The herpes simplex virus can also cause increased blood vessel growth, worsening vision, or complete loss of vision.
Your doctor may prescribe an antiviral drug such as trifluridine, vidarabine, or idoxuridine, which are usually prescribed as an ointment or solution that is applied to the eye several times a day. Sometimes, to help speed healing, the ophthalmologist has to gently scrape the cornea with a cotton-tipped swab to remove dead and damaged cells.
Shingles infection
Herpes zoster is a virus that grows in the nerves and can spread through the skin, causing very typical lesions. This disease does not necessarily affect the eye, it even appears on the face and forehead. But if the ophthalmic division of the fifth cranial nerve (trigeminal nerve) becomes infected, this infection will likely spread to the eye.
This infection causes pain, redness, and swelling of the eyelids. An infected cornea can swell, become severely damaged, and develop scarring. The most common complications of corneal infection include permanent glaucoma and lack of sensation when the cornea is touched.
When shingles infects the face and threatens the eye, early treatment with acyclovir given orally for 7 days reduces the risk of ocular complications. Corticosteroids, usually in the form of drops, can also be very helpful. Atropine drops are often used to keep the pupil dilated and help prevent increased eye pressure.
Peripheral ulcerative keratitis
This disease consists of an inflammation and ulceration of the cornea that usually appears in people who suffer from connective tissue diseases such as rheumatoid arthritis. This condition worsens vision, increases sensitivity to light, and produces the sensation that a foreign body is trapped in the eye.
Among people with rheumatoid arthritis and peripheral ulcerative keratitis, about 40% die within 10 years of the onset of peripheral ulcerative keratitis unless they undergo treatment. Treatments with drugs that suppress the immune system reduce the death rate to 8 percent in 10 years.
Keratomalacia
Keratomalacia (xerophthalmia, xerotic keratitis) is a disease in which the cornea becomes dry and opaque due to a deficiency of vitamin A, protein and calories in the diet. The surface of the cornea dies and ulcers and bacterial infections may appear. The tear glands and conjunctiva are also affected, resulting in inadequate tear production and dry eyes.
Night blindness (very poor vision in the dark) can develop due to a deficiency of vitamin A. Antibiotic drops or ointments can help cure infections, but it is even more important to correct the lack of vitamin A with vitamin supplements or solve malnutrition with an enriched diet or supplements.
Keratoconus
Keratoconus is a gradual change in the shape of the cornea, which ends up resembling a cone. The disease begins between 10 and 20 years of age. One or both eyes may be affected, causing major changes in vision and requiring frequent changes in glasses or contact lens prescriptions.
Contact lenses usually correct vision problems better than glasses, but sometimes the change in the shape of the cornea is so severe that contact lenses cannot be used or fail to correct vision. In extreme cases, a corneal transplant may be necessary.
Bullous keratopathy
Bullous keratopathy is a swelling of the cornea that appears more frequently in the elderly. In rare cases, bullous keratopathy occurs after eye surgery, such as cataract surgery. The swelling produces fluid-filled blisters on the surface of the cornea that can rupture, causing pain and decreased vision.
Bullous keratopathy is treated by reducing the amount of fluid in the cornea using saline solutions or soft contact lenses. In very rare cases, a cornea transplant is necessary.
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