A cataract is a clouding-over of the normally clear lens of the eye. The lens is located behind the iris and the pupil of the eye, and is responsible for adjusting the eye’s vision, and taking in light from the environment and focusing it onto the retina. The lens does this through an arrangement of proteins, which keeps the lens clear and lets the light through without being distorted. Cataracts form when some of these proteins clump together and affect the way that light filters through to the retina. This clouding, while generally painless, develops over time, and can affect vision in a variety of ways - making it more difficult to read, drive a car or see long distance.
There are three types of cataracts: subcapsular, nuclear, and cortical.
Subcapsular cataracts begin at the back of the lens, and are most common among people with diabetes
, farsightedness, retinitis pigmentosa (inherited degeneration of the retina, which results in night blindness
and decreased peripheral vision), or people who take high doses of steroids.
Nuclear cataracts are the most common type of cataract, since they are the cataracts that are age-related. With nuclear cataracts, the center of the lens becomes hard and changes color from white to yellow, yellow to amber. As this type of cataract develops, it becomes more difficult to differentiate between colors and to endure bright lights.
Cortical cataracts are wedge-shaped “spokes” in the eye’s cortex that develop from the outside of the lens towards its center. As the cataract reaches the center, these “spokes” begin to interfere with the passage of light through the lens, and cause a glare and loss of contrast. These cataracts develop slowly, but they can impair distance and near vision, so surgery is usually required early on. Cortical cataracts are also common with diabetics.
While some of the causes of age-related cataracts are outlined above, some people develop premature cataracts.
Types of premature cataracts include: secondary cataracts, which are formed after surgery for other eye problems
, or are formed in people who have other health problems; traumatic cataracts, which develop after eye injuries; congenital cataracts, which occur in babies or young children, often in both eyes, and as the result of a congenital condition such as an illness the mother had while she was pregnant; and radiation cataracts, which develop, as the name suggests, after exposure to some type of radiation.
Risk factors for the development of cataracts include:
St. John's Wort
- Exposure to ultraviolet light, or other types of radiation
- People with diabetes
- The use of steroids
- A low-antioxidant diet
- A high salt diet
- Cigarette smoke
- Air pollution
- Heavy alcohol consumption
- Recent studies have also suggested that St John's Wort may contribute to the development of cataracts
, also known as Hypericum Perforatum, is an herbal remedy often used for depression. Since it is most commonly used as a dietary supplement and not as a prescribed medication, the FDA has not closely monitored the herb, even though studies have shown that it is nearly as effective as brand-name medications in the treatment of depression.
Unfortunately, a recent study in the medical journal Current Eye Research
has concluded that there may be a link between the usage of St. John's Wort and the development of cataracts. According to this study, which interviewed over 31,000 people, those who had cataracts were 59% more likely to report usage of St. John's Wort. While this study was not conclusive, the results were compelling, and should give caution to anyone using St. John's Wort for any reason.
In the earliest stages of cataract development, the cloudiness may not cause vision loss, since the cataract is only covering a small part of the lens. When nuclear cataracts are developing, they actually can improve near vision for a short period of time, in a phenomenon called “second sight”.
As the cataract develops and grows larger more symptoms will develop, such as blurred vision, increased difficulty with night vision, light sensitivity, the need for brighter reading lights, frequent changes in eyewear prescriptions, color fading, and double vision in one eye. Halos or glares might also develop around bright lights, which could make activities like driving dangerous.
As mentioned earlier, cataracts usually develop slowly, and are almost always painless. The only time a cataract should be painful is if the cataract is allowed to become completely white, in a condition called an overripe- or hypermature- cataract. If these cataracts develop, they require removal.
Prevention & Treatment
Currently, there is no known prevention for cataracts, although antioxidants and some vitamins have been known to reduce the risk of developing cataracts.
Early-stage cataracts can usually be treated for a short period of time with the use of stronger corrective eyewear prescriptions, appropriate lighting, or another type of visual aid. As the cataracts develop, however, they may require surgery. Cataract surgery usually requires removing the cloudy lens, either by ultrasound waves (phacoemulsification) or an incision to the cornea (extracapsular surgery), and replacing it with a clear lens implant. In a few cases, the cataracts can be corrected without inserting implant lenses, and using eyeglasses or contact lenses instead.
Cataract surgery is a very common procedure in the United States, with a 95% success rate. As such, people are encouraged to surgically treat their cataracts as soon as the cataracts begin to interfere with their quality of life. There are a few risks involved, such as infection, bleeding, or a slightly higher risk of retinal detachment, but the vast majority of people experience better vision after the surgery.
- Eye Disorders
- St John's Wort
- Macular Degeneration
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