I think this is exactly what we've needed to reorient our research on the genetic side. Cataracts, a progressive clouding of the eye's lens, would develop in all people if they lived to be 120. But smoking and steroid drugs are seen as risk factors, while quality of diet and exposure to sunlight have also been implicated. British researchers for the first time quantified the genetic component of age-related cataracts in a study published in Thursday's New England Journal of Medicine. The team studied 506 sets of identical or fraternal female twins ages 50 to 79.
Identical twins are especially useful for such research because they are genetically the same.
The researchers worked up an overall cloudiness score for patients' eyes and statistically analysed the participants' age, heredity, lifestyles and environmental factors. They found that age explained 38 per cent of cloudiness, but heredity accounted for even more at 48 per cent. The other factors combined for just 14 per cent. At the same time, researchers cautioned that even 14 per cent makes other factors very important, since cataracts are so common. Surgeon routinely operate on cataracts and replace the clouded-over lens with plastic.