Cataracts are age-related thickenings in the lenses of the eyes that impair vision. If not surgically removed, they ultimately lead to blindness. Cataracts occur even in well-nourished individuals as a result of ultraviolet light exposure, oxidative stress, injury, viral infections, toxic substances and genetic disorders. Many cataracts, however, are vaguely called senile cataracts - meaning "caused by aging". In the United States, more than half of all adults 65 and older have a cataract. Oxidative stress appears to play a significant role in the development of cataracts, and the antioxidant nutrients may help minimize the damage. Studies have reported an inverse relationship between cataracts and dietary intakes of vitamin C, vitamin E and carotenoids. Taking supplements of vitamins C and E seems to reduce the likelihood of developing age-related cataracts.
As is pointed out in the passage, adults of 65 and over commonly develop cataracts ___.
as a result of genetic disorders
but only if they are under-nourished
which, if left untreated, eventually result in blindness
of a type that do not require surgical removal
which must be surgically removed, preferably before they start to impair vision
According to the passage, in the development of cataracts ___.
one important factor appears to be oxidative stress
there is always a combination of several factors
age is generally one of the least important factors
risk factors include carotenoids
exposure to ultraviolet light is the primary cause
We understand from the passage that vitamin C and vitamin E ___.
will ensure that a second cataract does not form
probably give some protection against visual loss
cannot serve as antioxidants in the elderly
are especially effective in the control of cataracts arising out of genetic disorders
are more effective than carotenoids in the control of oxidative stress