QALY (quality adjusted life year)
DALY (disability adjusted life year)
For example DALY score for blindness developed through cataracts is 0.570 So a 100 years of life with blindness is worth 43 years without.
Making your DALY estimates
"If you want, you can come up with your own personal quality weights. Think of an ailment that you have suffered from at some point in your life. Suppose you suffer from back pain, as I sometimes do. You could think to yourself: If 10 represents how good my life is when I’m perfectly healthy, how good is my life on a day when I’m suffering from back pain? This can be difficult to answer, so a way to make your judgments more precise is to ask yourself about what sorts of trade-offs you’d make. If you could live one extra day at perfect health or a certain larger number of days living with back pain, at what point would you be indifferent? In my own case, I’d be indifferent between living an extra four days perfectly healthy, or an extra five days with back pain. That suggests that I think life with back pain is 80 percent as good as life pain-free. In the endnotes, I link to some official lists of quality-of-life estimates, to help you assess the severity of different conditions yourself."