Environmental factors, including toxins, radiation, and ultraviolet light have cumulative effects which are worsened by the loss of protective and restorative mechanisms due to alterations in gene expression and chemical processes within the eye.Oxidative stress is an important pathogenic mechanism in cataract formation (see for review). Senile cataracts are associated with a decrease in antioxidant capacity in the lens. An increase in oxidative stress in the lens or a decrease in the ability to remove reactive oxygen species can lead to the lens becoming more opaque. Trauma
Blunt trauma causes swelling, thickening, and whitening of the lens fibers. While the swelling normally resolves with time, the white color may remain. In severe blunt trauma, or in injuries that penetrate the eye, the capsule in which the lens sits can be damaged. This damage allows fluid from other parts of the eye to rapidly enter the lens leading to swelling and then whitening, obstructing light from reaching the retina at the back of the eye. Cataracts may develop in 0.7 to 8.0% of cases following electrical injuries. Blunt trauma can also result in star- (stellate) or petal-shaped cataracts. Radiation
Cataracts can arise as an effect of exposure to various types of radiation. X-rays, one form of ionizing radiation, may damage the DNA of lens cells. Ultraviolet light, specifically UVB, has also been shown to cause cataracts, and some evidence indicates sunglasses worn at an early age can slow its development in later life.
A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble with bright lights, and trouble seeing at night. This may result in trouble driving, reading, or recognizing faces. Poor vision caused by cataracts may also result in an increased risk of falling and depression. Cataracts cause half of all cases of blindness and 33% of visual impairment worldwide.Cataracts are most commonly due to aging but may also occur due to trauma or radiation exposure, be present from birth, or occur following eye surgery for other problems. Risk factors include diabetes, longstanding use of corticosteroid medication, smoking tobacco, prolonged exposure to sunlight, and alcohol. The underlying mechanism involves accumulation of clumps of protein or yellow-brown pigment in the lens that reduces transmission of light to the retina at the back of the eye. Diagnosis is by an eye examination.Prevention includes wearing sunglasses and a wide brimmed hat, eating leafy vegetables and fruits, and avoiding smoking. Early on the symptoms may be improved with glasses. If this does not help, surgery to remove the cloudy lens and replace it with an artificial lens is the only effective treatment.