What are eye infections and disorders?

Causes and Symptoms

Several varieties of eye problems exist worldwide. Among the most important are corneal infections, ocular herpes, trachoma, conjunctivitis, iritis, cataracts, glaucoma, macular degeneration, diabetic retinopathy, styes, ptosis, ectropion, entropion, either watery or dry eyes, astigmatism, myopia, hyperopia, presbyopia, amblyopia, and keratoconus.

Many organisms can infect the eye. In corneal infections, bacteria, fungi, or viruses invade the cornea and cause painful inflammation and corneal infections called keratitis. Visual clarity is reduced, and the cornea produces a discharge or becomes destroyed, resulting in corneal scarring and vision
impairment.

Ocular herpes
is a recurrent viral infection by the herpes simplex virus. Symptoms are a painful sore on the eyelid or eye surface and inflammation of the cornea. More severe infection destroys stromal cells and causes stromal keratitis, cornea scarring, and vision loss or blindness. It is the most common infectious cause of corneal blindness in the United States.

Trachoma is a chronic and contagious bacterial disease of the conjunctiva and cornea. The eye becomes inflamed, painful, and teary. Small gritty particles develop on the cornea. Conjunctivitis is the inflammation of the conjunctiva caused by virus or bacteria infection, chemical irritations, physical factors, and allergic reactions. Inflammation of the cornea accompanies viral forms. The eyes become very sensitive to light. The infectious form is highly contagious, especially acute contagious conjunctivitis (pinkeye). Signs are red, extremely itching, and irritating eyes with a gritty feeling; tearing; nasal discharge; sinus congestion; swollen eyelids (in severe cases); and eyelids that may stick together from dry mucus formed during the night.

Iritis is inflammation of the iris. The cause is still under investigation, but it is associated with rheumatoid arthritis, diabetes mellitus, syphilis, diseased teeth, tonsillitis, trauma, and infections. Symptoms are red eyes, contracted and irregularly shaped pupil, extreme sensitivity to light, tender eyeball, and blurred vision.

A cataract is a clouding of the lens that causes a progressive, slow, and painless loss of vision. Symptoms are reduced night vision, blurriness, poor depth perception, color distortion, problems with glare, and frequent eyeglass prescription changes. Cataracts are the world’s leading cause of blindness. Causes are under investigation, but it could result from eye injury, prolonged exposure to drugs such as corticosteroids or to X rays, inflammatory and infectious eye diseases, complications of diseases such as diabetes, prolonged exposure to direct sunlight, poor nutrition, and smoking. Babies can be born with congenital cataracts.

Glaucoma is an optic nerve disease caused by fluid pressure that builds up abnormally within the eye because of very slow fluid production and draining. This can damage the optic nerve, retina, or other parts of the eye and result in vision loss. Early stages have no symptoms. Side (peripheral) vision is lost at an advanced point when irreversible damage makes vision restoration impossible. Blindness results if the condition is left untreated.

In macular degeneration, often called age-related macular degeneration (AMD or ARMD), the light-sensing cells of the macula, which is responsible for sharp and clear central vision, degenerates. The result is a slow, painless loss of central vision necessary for important activities such as driving and reading. Early signs are shadowy areas in the central vision, or fuzzy, blurry, or distorted vision. About 90 percent of cases are “dry” AMD, without bleeding, and 10 percent cases a more severe “wet” type, in which new blood vessels grow and leak blood and fluid under the macula, causing the most vision loss.

Diabetic retinopathy
is damage to the blood vessels of the retina caused by uncontrolled diabetes. Early signs may not be exhibited, but blurred vision, pain in the eye, floaters, and gradual vision loss are the symptoms in advanced cases.

A number of disorders can affect the eyelids. A stye, or hordeolum, is a painful localized swelling produced by infection or inflammation in a sweat gland of the eyelids or the sebaceous glands that secrete oil to stop the eyelids from sticking together. Ptosis is drooping of the upper eyelid that obstructs the upper field of vision for one or both eyes. It produces blurred vision, refractive errors, astigmatism, strabismus (in which the eyes are not properly aligned), or amblyopia (lazy eye). Symptoms include aching eyebrows, difficulty in keeping the eyelids open, eyestrain, and eye fatigue, especially during reading.

With an ectropion, the lower eyelid and eyelashes turn outward and sag, usually because of aging. Scarring of the eyelid caused by thermal and chemical burns, skin cancers, trauma, or previous eyelid surgery can also cause the problem. Symptoms are eye irritation, excessive tearing, mucus discharge, and crusting of the eyelid. With an entropion, the lower eyelid and eyelashes roll inward toward the eye and rub against the cornea and conjunctiva. This condition is also primarily the result of aging. Symptoms are irritation of the cornea, excessive tearing, mucus discharge, crusting of the eyelid, a feeling of something in the eye, and impaired vision. It can also be caused by allergic reactions, inflammatory diseases, and scarring of the inner surface of the eyelid caused by chemical and thermal burns.

Watery eyes
are caused by the blockage of the lacrimal puncta (two small pores that drain tear secretions from lacrymal glands that bathe the conjunctival surfaces of the eye) or oversecretion of the lacrimal glands. Dry eyes
result from inadequate tear production due to malfunction of the lacrymal (tear) glands, more common in women, especially after menopause. Symptoms are a scratchy or sandy feeling in the eye, pain and redness, excessive tearing following dry sensations, a stinging or burning feeling, discharge, heaviness of the eyelids, and blurred, changing, or decreased vision. Causes include dry air; the use of drugs such as tranquilizers, nasal decongestants, antidepressants, and antihistamines; connective tissue diseases such as rheumatoid arthritis; or the aging process.

Several refractive vision disorders are common. Astigmatism is blurred vision caused by a misshapen lens or cornea that makes light rays converge unevenly without focusing at any one point on the retina. In hyperopia (farsightedness), the eye can see distant objects normally but cannot focus at short distances because the eyeball is shorter than normal, causing the lens to focus images behind the retina. Presbyopia is farsightedness that develops with age. The lens gradually loses its ability to change shape and focus on nearby objects, creating difficulty in reading. In myopia (nearsightedness), the eye cannot focus properly on distant objects, although it can see well at short distances, because the eyeball is longer than normal. The lens cannot flatten enough to compensate and focuses distant objects in front of, instead of on, the retina.

Amblyopia, commonly called lazy eye, is a neurologic disorder in which the brain favors vision in one eye. Misalignment of the eyes (strabismus) creates two different images for the brain. If the condition goes untreated, then the weaker eye ceases to function.

Keratoconus is the progressive thinning of the cornea, producing conical protrusion of the central part of the cornea. It results in astigmatism or myopia and swelling or scarring of cornea tissue that ultimately impairs sight. Its causes are heredity, eye injury, and systemic diseases.

Treatment and Therapy

The treatment of eye infections and disorders depends on their cause and severity. Minor corneal infections are treated with antibacterial eyedrops. Intensive antibiotic, antifungal, and steroid eyedrop treatments eliminate the infection and reduce inflammation in severe cases. With ocular herpes,
prompt treatment with antiviral drugs stops the herpesvirus from multiplying and destroying epithelial cells. The resulting stromal keratitis, however, is more severe and therefore difficult to treat. The primary treatment for trachoma consists of three to four weeks of antibiotic therapy. Severe cases require surgical correction.

A conjunctivitis infection can clear without medical care, but sometimes treatment is necessary to avoid long-term effects of corneal inflammation and loss of vision. Treatment includes antibiotic eyedrops or ointments, antihistamine eyedrops or pills, decongestants, nonsteroidal anti-inflammatory drugs (NSAIDs), or mast-cell stabilizers. Artificial tears and warm compresses offer some relief. Tinted glasses reduce the discomfort of bright light.

With iritis, warm compresses can lessen the inflammation and pain. Certain steroid drugs produce quick reduction of the inflammation. A protective covering enables the eye to rest, and atropine drops could be used to dilate the pupils and prevent scarring or adhesions.

For cataracts, a stronger eyeglass prescription is recommended, but surgery that replaces the clouded lens with an artificial one is the only real cure. Drugs that keep the pupil dilated may help with vision.

Glaucoma detection is challenging because the disease is asymptomatic until it is advanced. Medical therapy is the first step for treatment. Glaucoma is difficult to cure, but some medications successfully lower pressure in the eye. If medication is ineffective, then laser surgery is applied to create openings and facilitate fluid draining in the eye.

One way to diagnose macular degeneration is by viewing a chart of black lines arranged in a graph pattern (Amsler grid). Early signs can be detected through retinal examination. No outright cure has been discovered, but some drug treatments may delay its progression or even improve vision.

Some cases of diabetic retinopathy
can be treated with laser surgery that shrinks or seals leaking and abnormal vessels on the retina. Vision already lost cannot be restored. A vitrectomy is recommended for some advanced cases, in which the vitreous component of the eye is surgically removed and replaced with a clear solution.

In treating a stye, applying hot compresses for fifteen minutes every two hours may help localize the infection and promote drainage. Mild antiseptics may be applied to prevent spread of the infection. A small surgical incision may be necessary in some cases.

Surgery is the treatment for congenital ptosis. The procedure tightens the levator muscle to lift the upper eyelid to the required position, allowing a full field of vision. For ectropion and entropion, surgery, under local anesthesia, is used to repair the abnormal eyelid before the cornea becomes infected and scarred. This is followed by an overnight patch and application of antibiotics for a week.

For dry eyes,
lubricating artificial tears in the form of eyedrops are the usual answer. Serious cases of watery eyes
may be treated by surgically closing the lacrimal puncta (tear drain) temporarily or permanently. Sterile ointments prevent the eye from drying at night.

Astigmatism is corrected with asymmetrical lenses that compensate for the asymmetry in the eye. Surgery and laser treatments are used to reshape the cornea and change its focusing power. Myopia is corrected by concave-shaped glasses or contact lenses that diverge light rays from distant objects to focus on the retina. Hyperopia and presbyopia are corrected with convex-shaped eyeglasses or contact lenses that converge light rays from nearby objects slightly before entering the eye, in order to focus on the retina. For those with amblyopia, a patch over the preferred eye forces the brain to use the other eye, but the drug atropine, which temporarily blurs vision in the preferred eye, offers a better medical alternative to eye patches.

For keratoconus, vision is corrected with eyeglasses initially, followed by special contact lenses that reduce distortion if astigmatism worsens. Corneal transplantation

becomes necessary when scarring becomes too severe. Preventive measures in strong sunlight are protective eyeglasses, sunglasses, and hats with brims.

Perspective and Prospects

Ancient papyri indicate that physicians of Egypt were the first to establish clinical practices for the treatment of eye infections and disorders. Herbs and eye paints with bacteriocidal properties, such as malachite, were used to prevent infections. Medicated ointments were used by Arab and Greek physicians to treat trachoma. Leukoma (a white spot on the cornea) was treated with animal galls, especially the gall of tortoise. Antimony sulfite and copper solutions were used to treat eyelid disorders. Herbs have been used in Africa, Asia, and Latin America to treat eye problems since ancient times.

In the twenty-first century, improved antibiotics and other chemicals are widely used to treat eye diseases. Technological advances in surgical procedures and laser techniques have provided additional options for treating vision disorders. Cataract surgery that once required several days of hospitalization is performed in less than thirty minutes on an outpatient basis. Multifocal lenses are designed to provide both near and distant vision that eliminates the use of reading glasses, advanced lens technology provide more foldable and flexible lens materials, and doctors use lasers to reduce secondary opacification in lenses. Immunotherapy is used to treat allergies that cause conjunctivitis.

Innovative research provides new knowledge and treatments for eye disorders. The Collaborative Longitudinal Evaluation of Keratoconus Study by the National Eye Institute (NEI) is investigating factors that influence the progression and severity of keratoconus. The NEI supported the clinical trials of the Herpetic Eye Disease Study that investigated treatments for severe ocular herpes, the most common infectious cause of corneal blindness in the United States.

Research that explored ayurvedic herbs of India has produced the isotine eyedrop, which effectively treats different eye disorders without surgery, including early stages of cataracts.

Functional MRI (fMRI) techniques allow researchers to create images of neurological activity in real time and to obtain insight into neurological eye diseases such as amblyopia. Scientists are conducting research to obtain implanted lens material that is able to form a new lens within the eye and that works efficiently with the original eye muscles. Investigations are in progress for glaucoma medications that reduce eye pressure and also protect the optic nerve. Research shows that antioxidants and nutrients such as zeaxanthin and lutein (found in green, leafy vegetables), zinc, and vitamins A, C, and E help to control AMD, and omega-3 fatty acids (abundant in coldwater fish) have a protective and healing effect against AMD.

The Food and Drug Administration (FDA) approved Lucentis in 2006 for treating the more severe “wet” AMD by monthly injections into the eye. Macugen (pegaptanib sodium), another AMD treatment medication that improves vision with six-week interval injections, was FDA-approved in 2004. In 2006, it was reported that a team of international research scientists discovered a protein called sVEGFR-1 that prevents blood vessels from forming in the cornea; it could become the basis of new treatments for cancer and macular degeneration. In 2012, research published in the journal Ophthalmology indicated that monthly injections of ranibizumab into the center of the eye halts the progression of scarring and the leaking of blood vessels in “wet” AMD sufferers. Stem cell research is also advancing the potentional for cures for AMD and other eye diseases and disorders.

Also in 2006, the HealthDay News reported that a visual aid invented by U.S. scientists comprising a tiny camera, a pocket-sized computer, and a transparent computer display mounted on a pair of glasses provides better vision and mobility for people with tunnel vision, who have lost their peripheral vision. Such innovations are welcome, since one in two hundred Americans over age fifty-five has tunnel vision, which is caused by diseases such as retinitis pigmentosa and glaucoma.

Early detection of signs and symptoms is a primary key to the treatment of all eye infections and disorders. As preventive measures, people must avoid eyestrain, exercise their bodies, eat healthy foods, control their sugar levels and blood pressure, avoid smoking, protect the eyes from sunlight, and have regular medical checkups.

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