The month of June is dedicated to raising our awareness of the fact that no one is exempt from the effects of aging, which often include cataracts. We don’t often consider the health of our eyes until that health diminishes or is robbed from us. Only then do we realize we have taken our eyesight for granted. It has often been said that our eyes are “our windows into the soul” but it could also be argued that they are the windows into the world, as well. It is a frightening experience to suddenly realize our windows are increasingly covered in a haze until we can no longer see clearly, or at all. Cataracts are similar to this experience. They begin with a haze or cloudiness that can’t be blinked away, but as it progresses, blindness can set in. Cataracts are the leading cause of blindness worldwide and the second leading cause of visual impairment.
The risk for cataracts begins to increase progressively around the age of 40 years and by 75 years of age, nearly half of all adults have cataracts. Among Caucasians, approximately 70 percent experience cataracts by the time they are 80 years old. Further, as lifespans continue to increase, the prevalence of cataract is expected to rise correspondingly. For example, in 2000, 20.48 million cases of cataracts were reported, but just one decade later a 25 percent increase was noted. Therefore, cataracts can present as a public health problem with numerous implications.
Cataracts affect the lens, which lies just behind the iris and pupil. In normal vision, light passes through a clear lens to the retina where it is converted to neural signals and interpreted by the brain as an image. However, when the lens becomes cloudy from a cataract, the image is hazy. The lens is also responsible for image focus and depth perception. It is comprised of water and neatly arranged protein and fiber molecules.
Cataracts most often occur when the protein molecules begin aggregating, disrupting the organized arrangement that is noted in a healthy lens. When proteins group together, light can no longer pass through clearly as it becomes partially blocked by the protein clumps. Cataracts grow larger as more protein joins the clumps and vision becomes increasingly obstructed. Protein phase separation and disturbance of the alignment of fiber cells in the lens are also potential causes of cataracts.
Cataracts have been associated with diabetes, smoking and alcohol use, and prolonged exposure to ultraviolet sunlight. Increased quantities of reactive oxygen species and the resulting oxidative stress most likely underlies the pathology of cataract formation, which is why it is often associated with aging – a state of increased oxidative damage. The lens fiber cells contain extremely high levels of the antioxidant, glutathione, indicating their propensity toward oxidation and their natural efforts to prevent oxidative damage. Further, glutathione is both produced and reduced in the lens, making it fully functional at its source. Aging individuals show larger quantities of oxidized glutathione compared to the overriding amounts of reduced glutathione in young, healthy individuals, against, giving evidence to the redox activity that occurs in the lens throughout life.
Many researchers suggest a genetic predisposition to cataracts. Specific genes linked to cataract development have not been discovered, but studies of twins and familial associations have suggested that heredity can account for approximately 30 to 60 percent of cataract risk.
If oxidative stress fosters cataract development and progression, antioxidants should go far in helping to prevent cataract formation. One animal study sought to determine the association between consuming antioxidants and cataracts by measuring lens chaperone activity which is altered by oxidative stress. In this study, antioxidant consumption resulted in less severe central opacities, slower stage cataracts, and protected chaperone activity in the lens of selenite cataract rats.
Curcumin, a powerful antioxidant, has been receiving more attention among researchers as a potential anti-cataract agent. Both in vivo and in vitro studies have shown that curcumin decreases the markers of oxidation and significantly increases antioxidant activity, protecting cells from oxidative damage in selenite cataract rats.
With an aging population and a high prevalence of cataracts, it is vital that we continue to focus on promoting and maintaining a high intake of antioxidants, both through the diet and in supplementation. Cataracts are widely recognized as the outcome of oxidative damage in the lens, so antioxidants are the solution to protecting our “windows” to both the soul and the world around us.