Cataracts: 3 common types, causes, symptoms and treatments
By Gretchyn Bailey; reviewed by Vance Thompson, MD
Cataract is the clouding of the eye's natural lens. It is the most common cause of vision loss in people over age 40 and is also the principal cause of blindness in the world. Types of cataracts include:
- A subcapsular cataract occurs at the back of the lens. People with diabetes or those taking high doses of steroid medications have a greater risk of developing a subcapsular cataract.
- A nuclear cataract forms deep in the central zone (nucleus) of the lens. Nuclear cataracts usually are associated with aging.
- A cortical cataract is characterized by white, wedge-like opacities that start in the periphery of the lens and work their way to the center in a spoke-like fashion. This type of cataract occurs in the lens cortex, which is the part of the lens that surrounds the central nucleus.
Cataract symptoms and signs
At first, a cataract has little effect on your vision. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass or viewing an impressionist painting.
Hazy, blurred vision may mean you have a cataract.
A cataract may make light from the sun or a lamp seem too bright or glaring. Or you may notice when you drive at night that the oncoming headlights cause more glare than before. Colors may not appear as bright as they once did.
The type of cataract you have will affect exactly which symptoms you experience and how soon they will occur. When a nuclear cataract first develops, it can bring about a temporary improvement in your near vision, called "second sight."
Unfortunately, the improved vision is short-lived and will disappear as the cataract worsens. On the other hand, a subcapsular cataract may not produce any symptoms until it's well-developed.
If you think you have a cataract, see an eye doctor for an exam to find out for sure.
NEED AN EYE EXAM? Find an eye doctor near you and make an appointment.
What causes cataracts?
The lens inside the eye works much like a camera lens, focusing light onto the retina for clear vision. It also adjusts the eye's focus, letting us see things clearly both up close and far away.
The lens is mostly made of water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it.
But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract, and over time, it may grow larger and cloud more of the lens, making it harder to see.
No one knows for sure why the eye's lens changes as we age, forming cataracts. But researchers worldwide have identified factors that may cause cataracts or are associated with cataract development.
Besides advancing age, cataract risk factors include:
- Ultraviolet radiation
- Prolonged use of corticosteroid medications
- Statin medicines used to reduce cholesterol
- Previous eye injury or inflammation
- Previous eye surgery
- Hormone replacement therapy
- Significant alcohol consumption
- High myopia
- Family history
One theory of cataract formation is that many cataracts are caused by oxidative changes in the human lens. This is supported by nutrition studies that show fruits and vegetables high in antioxidantsmay help prevent certain types of cataracts.
Though there is significant controversy about whether cataracts can be prevented, a number of studies suggest certain nutrients and nutritional supplements may reduce your risk of cataracts.
One 10-year study of female health professionals found that higher dietary intakes of vitamin E and the carotenoids lutein and zeaxanthin from food and supplements were associated with significantly decreased risks of cataract.
Good food sources of vitamin E include sunflower seeds, almonds and spinach. Good sources of lutein and zeaxanthin include spinach, kale and other green, leafy vegetables.
Other studies have shown antioxidant vitamins such as vitamin C and foods containing omega-3 fatty acids may reduce cataract risk.
Another step you can take to reduce your risk of cataracts is to wear sunglasses that block 100 percent of the sun's UV rays when you are outdoors.
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