The “ABCs” of Cataract
A cataract is the clouding of the eye’s lens due to clumping of lens protein and discoloration of the lens because of age, smoking, sunlight exposure, the use of certain drugs, and diabetes.
The lens consists mostly of water and protein. When the protein clumps up, it clouds the lens and reduces the light that reaches the retina, causing blurred vision. Most age-related cataracts develop from protein clumping.
The clear lens also slowly colors with age. This gradual darkening doesn’t affect the sharpness of the image transmitted to the retina, but it can make it more difficult to distinguish between colors such as blues and purples.
Nuclear cataract, which occurs in the central portion of the lens, is the most common type of cataract among older people, especially women. Cataract can develop in other locations too. Cortical cataract is found at the outside edge of the lens, while posterior subcapsular cataract (PSC, the least common type) forms at the back surface of the lens beneath the lens capsule.
Helping to Keep Cataracts at Bay
Damage to lens proteins can happen gradually from a variety of causes, including the formation of free radicals due to light exposure. Antioxidants such as vitamin C and lutein / zeaxanthin are believed to play an important role in mopping up those free radicals or filtering out harmful blue light.
Two recently published studies suggest that there are steps we can take to help protect the eye’s lens. One study identifies risk factors that we can do something about, while the other report adds weight to the idea that lutein and zeaxanthin may play a protective role.
Lutein & Zeaxanthin Tied to Cataract Risk
Finnish researchers recently looked at whether blood levels of lutein and zeaxanthin are related to nuclear cataract in over 1,600 older participants (1).
People who had the highest blood levels of lutein and
zeaxanthin had a 40% lower risk of having nuclear cataract, compared with the group who had the lowest blood levels.
Risk Factors linked to Cataract Types
University of Southern California researchers tracked risk factors for different types of cataract in nearly 6,000 people participating in the Los Angeles Latino Eye Study (2).
It’s no surprise that older age increased the risk for most of the cataract types except PSC, where higher systolic blood pressure and a history of diabetes were identified as risk factors.
For cortical cataract, a history of diabetes and higher hemoglobin A1c raised risk, while smoking and myopia (myopic refractive error) emerged as risk factors for nuclear type cataract. Myopia is nearsightedness, where distant objects appear out of focus. Hemoglobin A1c is the best measure of blood sugar control over time.
Finally, myopic refractive error, history of diabetes, higher systolic blood pressure, and presence of large drusen were independent risk factors for mixed cataract, where more than one lens location was involved. The presence of large drusen is predictive of developing advanced macular degeneration (AMD).
Steps We Can Take
In addition to getting regular eye exams and not smoking, make sure to:
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