problems. Risk factors include diabetes, longstanding use of corticosteroid medication, smoking tobacco, prolonged exposure to sunlight, alcohol. and extended hyperbaric oxygen therapy. 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. Wearing sunglasses and a wide brimmed hat in bright sunlight, eating leafy vegetables and fruits, and avoiding smoking may have some preventative effect. Early 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. Cataract surgery is not readily available in many countries, and is needed only if the cataracts are causing problems. Surgery with implants generally results in better vision and an improved quality of life. About 20 million people worldwide are blind due to cataracts. Cataracts cause 51% of all cases of blindness and 33% of visual impairment worldwide. They are the cause of approximately 5% of blindness in the United States and nearly 60% of blindness in parts of Africa and South America. Blindness from cataracts occurs in about 10 to 40 per 100,000 children in the developing world, and 1 to 4 per 100,000 children in the developed world. Cataracts become more common with age. In the United States, cataracts occur in 68% of those over the age of 80 years. They are more common in women, and less common in Hispanic and Black people. Contraindications Contraindications to cataract surgery include cataracts that do not cause visual impairment, and medical conditions that predict a high risk of unsatisfactory surgical outcomes. Implantation of posterior chamber intraocular lens (PCIOL) in patients below 7 months of age is controversial due to rapid ocular growth at this age. Ocular growth in infants is not entirely predictable, and an early implant is likely to result in large refractive error later in childhood. Congenital cataracts may also be caused by factors which make the eye more susceptible to an excessive amount of inflammation, which may be very difficult to control. Intraocular lenses are associated with a greater risk of visual axis opacities in this age group. Optical correction in these patients without intraocular lens (aphakic) is usually managed with either special contact lenses or glasses. Secondary implantation of IOL (placement of a lens implant as a