A company developing an artificial retina to help the blind see is trying to determine the quality of life for blind people.

• The company first surveys a group of sighted people using a time trade-off (TTO) approach. The results indicate that being blind should be assigned a quality weight ofq=0.4.
• The company then surveys a group of people who recently became blind due to accidents or glaucoma. The results indicate that being blind should be assigned a quality weight ofq=0.1.
• Finally, the company surveys a group of people who were not born blind but became blind over twenty years ago. The results indicate that being blind should be assigned a quality weight ofq=0.9.

1. Explain why these three approaches might return different quality of life estimates. Why might people who have lived with blindness for a long time rate their quality of life so much higher than people who have only recently become blind?
2. For a cost-effectiveness study of a drug that may, as a side-effect, result in blindness, which of these quality weight measures is most appropriate?
3. Now suppose researchers are measuring the cost-effectiveness of artificial retinas, which may be able to restore sight to the blind. Does this change your answer about which quality of life measure to use?