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Welcome to Optic Atlantis, a space totally dedicated to the world of optics and its components that you can view and retrieve information about optics. The function of this site is to help you better understand your eyes and your vision.



domingo, 21 de agosto de 2011

Blepharitis

Blepharitis is an inflammation of the eyelids causing red, irritated, itchy eyelids and the formation of dandruff-like scales on eyelashes. It is a common eye disorder caused by either bacterial or a skin condition such as dandruff of the scalp or acne rosacea. It affects people of all ages. Although uncomfortable, blepharitis is not contagious and generally does not cause any permanent damage to eyesight.
Blepharitis is classified into two types:
Anterior blepharitis occurs at the outside front edge of the eyelid where the eyelashes are attached.
Posterior blepharitis affects the inner edge of the eyelid that comes in contact with the eyeball.
Individuals with blepharitis may experience a gritty or burning sensation in their eyes, excessive tearing, itching, red and swollen eyelids, dry eyes, or crusting of the eyelids. For some people, blepharitis causes only minor irritation and itching. However, it can lead to more severe signs and symptoms such as blurring of vision, missing or misdirected eyelashes, and inflammation of other eye tissue, particularly the cornea.
In many cases, good eyelid hygiene and a regular cleaning routine can control blepharitis. This includes frequent scalp and face washing, using warm compresses to soak the eyelids, and doing eyelid scrubs. In cases where a bacterial infection is the cause, various antibiotics and other medications may be prescribed along with eyelid hygiene.
Two types of Blepharitis:

-Anterior blepharitis is commonly caused by bacteria (staphylococcal blepharits) or dandruff of the scalp and eyebrows (seborrheic blepharitis). It may also occur due to a combination of factors, or less commonly may be the result of allergies or an infestation of the eyelashes.

-Posterior blepharitis can be caused by irregular oil production by the glands of the eyelids (meibomian blepharitis) which creates a favorable environment for bacterial growth. It can also develop as a result of other skin conditions such as acne rosacea and scalp dandruff.

Blepharitis can be diagnosed through a comprehensive eye examination. Testing, with special emphasis on evaluation of the eyelids and front surface of the eyeball, may include:
Patient history to determine any symptoms the patient is experiencing and the presence of any general health problems that may be contributing to the eye problem.
External examination of the eye, including lid structure, skin texture and eyelash appearance.
Evaluation of the lid margins, base of the eyelashes and meibomian gland openings using bright light and magnification.
Evaluation of the quantity and quality of tears for any abnormalities.
A differentiation among the various types of blepharitis can often be made based on the appearance of the eyelid margins:
Staphyloccal blepharitis patients frequently exhibit mild sticking together of the lids, thickened lid margins, and missing and misdirected eyelashes.
Seborrheic blepharitis appears as greasy flakes or scales around the base of eyelashes and a mild redness of the eyelids.
Ulcerative blepharitis is characterized by matted, hard crusts around the eyelashes that when removed, leave small sores that ooze and bleed. There may also be a loss of eyelashes, distortion of the front edges of the eyelids and chronic tearing. In severe cases, the cornea, the transparent front covering of the eyeball, may also become inflamed.
Meibomian blepharitis is evident by blockage of the oil glands in the eyelids, poor quality of tears, and redness of the lining of the eyelids.
Using the information obtained from testing, your optometrist can determine if you have blepharitis and advise you on treatment options.

Acanthamoeba

Acanthamoeba is one of the most ubiquitous organisms in the environment, but rarely causes infections. When infection does occur, however, it can be extremely serious and vision threatening. Recently, there have been multiple reports of increasing incidence of Acanthamoeba keratitis. Co-infection with a bacterial keratitis is common both in the contact lens case and on the cornea, complicating prevention, diagnosis and treatment.
By educating yourself about the symptoms and risk factors for Acanthamoeba keratitis, you can help protect yourself from this potentially sight-threatening infection. The best defense against Acanthamoeba keratitis infection is proper contact lens hygiene.

Symptons:
-A red, (frequently) painful eye infection—especially if the discomfort does not improve with treatment.
-Foreign body sensation, tearing, light sensitivity, and blurred vision.
-Red, irritated eyes lasting for an unusually long period of time after removal of contact lenses.

Risk Factors:
-Use of tap water in cleaning and disinfecting contact lenses—including the lens case.
-Swimming with contact lenses in the eyes, especially in fresh water lakes and rivers. Acanthamoeba keratitis has also been isolated from virtually all water sources—from pools to hot tubs to showers.

What you should do:
-Always wash hands before handling contact lenses.
-Rub and rinse the surface of the contact lens before storing.
-Use only sterile products recommended by your optometrist to clean and disinfect your lenses. -Saline solution and rewetting drops are not designed to disinfect lenses.
-Avoid using tap water to wash or store contact lenses.
-Contact lens solution must be discarded upon opening the case, and fresh solution used each time the lens is placed in the case.
-Replace lenses using your doctor’s prescribed schedule.
-Do not sleep in contact lenses unless prescribed by your doctor and never after swimming.
-Never swap lenses with someone else.
-Never put contact lenses in your mouth.
-See your optometrist regularly for contact lens evaluation.
-If you experience RSVP (redness, secretions, visual blurring or pain), return to your optometrist immediately!

Eye Working Process

Vision begins when light rays are reflected off an object and enter the eyes through the cornea, the transparent outer covering of the eye. The cornea bends or refracts the rays that pass through a round hole called the pupil. The iris, or colored portion of the eye that surrounds the pupil, opens and closes (making the pupil bigger or smaller) to regulate the amount of light passing through. The light rays then pass through the lens, which actually changes shape so it can further bend the rays and focus them on the retina at the back of the eye. The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones, which are named for their distinct shapes. Cones are concentrated in the center of the retina, in an area called the macula. In bright light conditions, cones provide clear, sharp central vision and detect colors and fine details. Rods are located outside the macula and extend all the way to the outer edge of the retina. They provide peripheral or side vision. Rods also allow the eyes to detect motion and help us see in dim light and at night. These cells in the retina convert the light into electrical impulses. The optic nerve sends these impulses to the brain where an image is produced.

Low Vision

Few people are totally without sight. Most individuals today classified as "blind" actually have remaining sight and, thanks to developments in the field of low vision rehabilitation, can be helped to make good use of it, improving their quality of life.
Anyone with noncorrectable reduced vision is visually impaired, and can have a wide range of problems.
The World Health Organization uses the following classifications of visual impairment. When the vision in the better eye with best possible glasses correction is:
20/30 to 20/60 is considered mild vision loss, or near-normal vision
20/70 to 20/160 is considered moderate visual impairment, or moderate low vision
20/200 to 20/400 is considered severe visual impairment, or severe low vision
20/500 to 20/1,000 is considered profound visual impairment, or profound low vision
less than 20/1,000 is considered near-total visual impairment, or near total blindness
no light perception is considered total visual impairment, or total blindness.
There are also levels of visual impairment based on visual field loss (loss of peripheral vision).
In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees or less of visual field remaining, is considered legally blind.
Visual impairments take many forms and exist in varying degrees. It is important to understand that visual acuity alone is not a good predictor of the degree of problems a person may have. Someone with relatively good acuity (e.g., 20/40) can have difficulty functioning, while someone with worse acuity (e.g., 20/200) might not be having any real problems.

Eye Care

Eye care is essential to maintaining the health of our eyes. People with eye diseases that greatly affect their vision face many problems. They are physically hampered by impaired vision. They are not able to perform daily activities like driving or working. Some are barely able to see or have lost their vision entirely. They are also faced with emotional stress. People with dramatic eye problems face many issues that can lead to solitude and depression. This strain also affects friends and families.
They are not able to enjoy everyday moments or special events. Eye problems can also be very costly to individuals. The need for eye wear, eye surgeries, and other needs can greatly affect a person or a family is income. Some people are not even able to work because of their eye problems. There are several steps everyone can take to help prevent eye diseases and the problems related to them. It starts with knowledge of keeping the eye healthy and following good guidelines for maintaining good eye health.
There are many eye diseases that can be prevented or whose progression can be slowed down with proper precautions and healthy eating. Eating a lot of Vitamins A, E, C, and some Zinc and Selenium can help prevent many diseases including those that affect the eyes. Visit the nutrition page on what foods contain these vitamins and minerals. Certain diseases might be causes by other factors such as obesity, diabetics, exposure to ultraviolet light, smoking, certain medications such as steroids, and many other factors. It is a good idea to ask your eye care doctor for specific steps you can take. People with obesity or who are diabetic should have more routine checkups since they are more likely to develop certain eye diseases.
Those who are outside most of the day should use protective sunglasses or eyeglasses to prevent heavy exposure to ultraviolet light. People who smoke or take certain medications should ask their doctor if they are more likely to have eye diseases because of family background. These little measures can help your eyes healthy and keep all the emotional, physical, and financial problems that come with eye problems away.