All About Healthy Eyes
- Eyes are said to be the windows to our souls, but they are also windows to the world and need to be kept clear and in good working order. Eyes need protection from many environmental assaults (including bacteria or other contaminants), ultraviolet light, and foreign objects ranging from flying sparks in a chemistry lab to an errant racquetball on the court.
Contaminants and Eye Disease
Severe eye infections among people improperly using homemade saline solutions for soft contact lenses have been reported to the Food and Drug Administration over the last few years. The FDA has sent 50,000 plus letters to eye-care practitioners nationwide to warn them of this problem. Certain species of Acanthamoeba (a kind of parasite) were present in homemade solutions because the prepared solutions were not sterile. A study by the Centers for Disease Control in Atlanta found that people were not using the product correctly. For example, they were using the solutions as a rinse after heat disinfections, or in eye drop form, thus possibly introducing a contaminated solution into the eye.
In the alert, FDA recommends that users of homemade saline:
- Use homemade saline solutions only before or during heat disinfections.
- Never use after heat disinfection -- for example, for cleaning before putting in eyes.
- Never use with chemical or hydrogen peroxide disinfections.
- Never use directly in the eye or as a wetting solution.
- Prepare fresh saline solution daily.
- Sterilize solution bottle with boiling water at least once a week.
- Avoid swimming with contact lenses in place because of danger of bacterial contamination from pool or sea water.
Recently, FDA investigated reports of corneal ulcers with long-term use of extended-wear contact lenses. Corneal ulcers can cause scarring to the cornea, leading to vision loss, including partial or complete blindness. Recent studies show that wearing either daily- or extended-wear lenses for too long increases the risk of corneal ulcers, as does smoking. While the overall risk of corneal ulcers is small, the relative risk of extended-wear to daily-wear is approximately 5 to 1. Originally designed and marketed for use from 1 to 30 days, these lenses are now being recommended only for week-long wear at the most.
Ultraviolet Light and Eye Damage
Not only must our eyes be protected from disease for healthy eyes, but also from ultraviolet light. UV light emanates from the sun naturally or from special lamps (such as sun lamps). There are three types of ultraviolet light: UVA, UVB and UVC.
UVC light is normally screened out by the ozone layer and so far does not present an immediate threat. UVB light can cause the greatest eye damage. Overexposure to intense UVB light can damage the cornea, producing a painful condition known as photo keratitis. While recovery occurs over several days, the eye often must be bandaged. Many scientists think there is a link between prolonged exposure to UVB light and the formation of lens cataracts. Some studies also show a possible link between UVA light and cataract formation. Because UVA light can reach the retina, researchers are studying whether long-term exposure may be related to loss of vision in old age.
Sunglasses offer the best eye protection from UV light, better than visor hats or parasols. To help consumers make the most informed choice of eye wear to protect them from ultraviolet exposure, FDA and the Sunglass Association of America have developed a labeling agreement, under which sunglass labels will indicate the "use category" of the product. The categories, representing different levels of protection appropriate for different outdoor environments, are:
- Cosmetic (lightly tinted lenses for use in non-harsh sunlight) -- Screens at least 70 percent of UVB, 20 percent of UVA, and less than 60 percent of visible light.
- General Purpose (medium to dark tinted lenses for use in most outdoor activities, such as boating, flying and hiking) -- Screens at least 95 percent of UVB, 60 percent of UVA, and 60 to 92 percent of visible light.
- Special Purpose (recommended for use in very bright environments, such as when skiing, mountain climbing, or at tropical beaches) -- Screens at least 99 percent of UVB, at least 60 percent of UVA, and 20 to 97 percent of visible light.
In addition, the agreement encourages manufacturers to list the actual amount of UVA and UVB the product blocks. If this information doesn't appear on the label, consumers might want to check with the manufacturers to find out how much UVA and UVB light is screened out by these lenses. Sunglasses should not be worn when it's dark because they compromise night vision. That also goes for tinted contact lenses.
Under the agreement, manufacturers will provide point-of-sale brochures explaining concerns about UV light and how to best take advantage of the information provided in the labels.
Protective sunglasses, however, are not sufficient for people exposed to UV lamps, such as those found in tanning booths. FDA requires tanning salons to make special protective goggles available to their customers.
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To help protect against damage from foreign objects striking or entering the eye, FDA requires that all eyeglass lenses be "impact resistant," although not necessarily shatterproof. Impact resistance is measured by the "drop ball test" -- dropping a 5/8-inch steel ball weighing approximately one-half ounce from a height of 50 inches onto the horizontal upper surface of the lens. To meet FDA regulations, the lens must not crack through all thicknesses, nor may any pieces chip off, nor any crack run the diameter of the lens. This requirement holds true for glass, plastic and laminated glass lenses. Industrial safety glasses are not regulated by FDA, but by the Occupational Safety and Health Administration, which has additional requirements for impact resistance for those industrial uses.
Cosmetics should be considered foreign objects capable of causing eye irritation. Contact lens wearers should insert their lenses before applying makeup, especially liquid foundation. According to a two-part report published in the May and June 1980 issues of Consumer Reports, mascara should be replaced three or four times a year due to the possibility of bacterial contamination. The wands come into contact with airborne bacteria and become contaminated, which can cause eye infections. Hair spray should not be used once contact lenses have been inserted; the spray clings to lenses and cannot be removed.
Routine Eye Care
Basic eye care can go far to protect eyes on a day-to-day basis. Disease prevention begins in childhood. Ideally, children's eyes should be checked periodically by their health-care practitioners, with the first thorough examination by the time the child enters school. Children who have hereditary or congenital problems such as "lazy eye" might need earlier and more frequent monitoring.
From adolescence thru adulthood, barring any problems, eyes should be examined every five years for good eye health, not merely to check for vision changes, but for early detection of diseases such as glaucoma. People with impaired vision should be followed at intervals recommended by their eye-care practitioners. If a change in vision is noticed between regularly scheduled visits, more frequent examinations may be required.
Eye-care practitioners include ophthalmologists, optometrists and opticians. Ophthalmologists are physicians and surgeons who specialize in the diagnosis and treatment of eye disease. They also perform vision tests and prescribe glasses and contact lenses.
Optometrists are state-licensed professionals who examine for visual defects and prescribe glasses and contact lenses. Optometrists can diagnose eye diseases, and in some states are licensed to prescribe medicines and manage certain eye diseases, but they do not perform surgery. Opticians fill prescriptions for eyeglasses, and in some states are licensed to fill prescriptions for contact lenses as well.
The most common vision defects that require corrective lenses are myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. As the name suggests, a nearsighted person can see close-up objects clearly, while those at a distance become less distinct. Farsightedness is the opposite condition and may result in blurriness at all distances. In both conditions light does not focus properly on the retina. In myopia, the eyeball is elongated and light focuses in front of the retina. In hyperopia, the eyeball is shortened and light focuses at a point in back of the retina. Astigmatism is caused by an irregularity in the shape of the cornea that causes light to focus in different planes. Corrective lenses reduce the multiple images and refocus them to the retina.
Eyeglass frames can also play a role in eye safety. Well-fitted frames should neither pinch the bridge of the nose nor lie too heavily behind the ears. Thicker lenses require heavier frames. The ideal color for tinted lenses is gray because it is the most neutral in the color spectrum, letting most colors appear in their natural hue. Green and brown are considered next best. Darkly tinted lenses should be limited to outdoor use because they can severely limit visibility indoors.
Contact lenses require greater care than eyeglasses because they come into direct contact with the eye. Whatever is on the lens -- dust, pollen, bacteria, and chemicals -- also reaches the eye's surface. Always follow the eye-care practitioner's directions, as well as all manufacturer's instructions. The eye-care practitioner should also be consulted about the various types of solutions and cleaning methods for contact lenses.
There are three types of contact lenses: hard, soft, and oxygen -- (gas) permeable. Each is fashioned out of a slightly different material, requiring different care.
Hard lenses were the first type marketed. According to James Saviola, an optometrist in FDA's division of ophthalmic devices, hard lenses are fashioned from the same material originally used to make airplane windshields. Of the contact lens types, they are best able to correct astigmatism because they form a new front surface to counteract the irregular cornea. It takes several weeks for the wearer to become adjusted to hard lenses, however, and they should be worn according to a schedule for maximum benefit.
Because the material from which hard lenses are made does not admit oxygen to the eye, after a few hours the eye will begin to swell. Hard lens wearers must remove their lenses after about 12 hours of use and rely on eyeglasses for the rest of the day. To overcome this problem, oxygen-permeable lenses were developed. Because these are actually a type of hard lens, the period of adjustment and routine wearing schedules are similar to the break-in period of regular hard lenses.
Soft contact lenses are made of various types of water-absorbing plastics that allow oxygen to reach the eye. They are easier to adjust to than hard contact lenses, usually requiring no more than a week until they are comfortable. They are less likely than hard lenses to dislodge when playing sports, but they are less durable and may need to be replaced every year.
Soft lenses require careful attention to cleaning, rinsing and disinfections. Daily-wear soft contact lenses need to be cleaned daily and, as with hard and oxygen-permeable lenses, must be removed for sleeping. Extended-wear soft contact lenses can be left in the eye while sleeping, but, as mentioned previously, must be removed at least once a week for cleaning.
Don't be afraid to ask eye-care professionals whatever questions are necessary to understand their instructions. Make sure you know what brand of lenses you have and what eye-care products are specifically formulated for those lenses. Learn to recognize signs of trouble that can alert you to serious problems: *red or painful eyes
- sudden changes in vision
- repeated irritation of the eye
- excess secretions from the eyes.
If you develop any unusual or severe symptoms, see an eye-care specialist immediately, even if that means a trip to a hospital emergency room.
Eye safety requires only a little education and a lot of common sense. Take care of your windows to the world, and they will reward you with all that world's visual delights. . . by Jessica Auerbach