• Conjunctivitis is a highly contagious infection that causes red, itchy eyes.Eye image by Igor Tsaranenko from Fotolia.com
  
  Most people experience a problem with their eyes at some point during their lives. Allergies may make your eyes itchy and red, or your eyes may feel strained after a long day in front the computer. Many of these conditions require little intervention and usually resolve themselves on their own. Some eye aliments, however, warrant a visit to the doctor or a trip to the drugstore for a specialty treatment.
  
  

Sty

• A sty is an abscess that occurs on the eyelid as a result of a bacterial infection. The bacteria that cause a sty actually occur naturally on the skin of the eyelid and do not usually present a problem. When some of the bacteria become trapped along with dead skin cells in pockets along the eyelid, however, a sty forms. Sties are usually visible on the surface of the eyelid, but some may form deeper inside where they cannot be seen. Most sties are caused by staphylococcal bacteria but are usually harmless. They may affect individuals of all ages and are likely to reoccur throughout a person's life.
  
  In most cases, you can treat sties at home with warm compresses and over-the-counter ointments. Sties are usually not contagious, but it is best to avoid sharing washcloths, towels or eye makeup with others.
  
  

Conjunctivitis

• Commonly known as pink eye, conjunctivitis is an infection of the transparent membrane that covers the eyelid and part of the eyeball. The membrane becomes inflamed, giving it the pink or red appearance associated with the condition. Conjunctivitis is usually caused by a bacterial or viral infection or an allergic reaction. Symptoms include redness, itchiness and a feeling of grittiness in the eye. Some individuals also experience discharge or tearing.
  
  Conjunctivitis is highly contagious, so if you suspect that you have pink eye, consult a doctor as soon as possible.
  
  Antibiotic eyedrops are prescribed for cases caused by bacterial infection, and allergy-relief eyedrops are administered to individuals with allergy-induced conjunctivitis. In the case of viral conjunctivitis, there is no medication to treat it. The infection must run its course, which can take up to three weeks.
  
  

Cataracts

• A cataract occurs when the natural lens behind the eye's iris and pupil begins to cloud. It is caused by proteins in the lens massing together, so vision eventually becomes blurred. Cataracts generally occur in elderly people, but individuals with diabetes or severe farsightedness and those who are on high doses of steroids also may be prone to cataracts. They usually start out small but begin to worsen over time.
  
  There are three types of cataracts: a subcapsular cataract, which begins at the back of the lens; a nuclear cataract, which forms in the center of the lens; and a cortical cataract, which forms in the cortex of the lens.
  
  The only treatment for cataracts is surgery performed by an ophthalmologist. He removes the problem lens and replaces it with a plastic intraocular lens. In most cases, individuals experience fully restored vision after the procedure, which is typically between 20/20 and 20/40.
  
  

Glaucoma

• When individuals develop glaucoma, an excess of fluid pressure builds up inside the eye. The pressure, known as intraocular pressure, may affect the optic nerve, which is responsible for transmitting visual images to the brain. If glaucoma inflicts enough damage to the optic nerve, loss of vision is possible. In most cases, permanent blindness occurs within a few years.
  
  There are usually no early symptoms of the condition, but glaucoma is typically inherited, so people with a family history should begin having regular screenings with an ophthalmologist after the age of 40. Individuals with diabetes should also be tested regularly.
  
  Common treatments for glaucoma include eyedrops to reduce fluid formation or improve its outflow; laser surgery which helps improve fluid outflow slightly; and microsurgery called trabeculectomy, which drains the fluid and reduces intraocular pressure. While no preventive measures exist for glaucoma, it can be controlled if diagnosed early enough.