Question

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 tradeoff (TTO) approach. The results indicate that being blind should be assigned a quality weight of q=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 of q = 0.1.2 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 of q = 0.9.- a) 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?- (b) 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? (©) 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?

Answer 1

a) These three approaches might return different quality of life estimates as the sample surveyed contains a different set of people. As shown according to the surveys, people who have lived with blindness for a long time will rate their quality of life much higher than those who have become recently blind. It is likely that these people who have been blind for a long time would have got used to it to the point that it does not affect their lives much anymore and have come to terms with it. However those who have only recently become blind will find it to be a serious difficulty in their day to day life and may even have been traumatized psychologically.

b) For a cost effectiveness study of a drug that may, as a side effect,result in blindness, the quality of life measures most appropriate will be q=0.1 (that of the survey of those who have recently become blind). Since the drug may have a side effect of causing blindness, it may cause people with vision to enter blindness(People represented by the second set) and this quality of life measure will be the most appropriate to represent this.

c) Now supposing researchers are measuring the cost effectiveness of artificial retinas which may restore sight to the blind. This changes the answer about which quality of life measure to use as the people it will help will also mostly include the ones that have been blind for a long time. The quality of life measure 0.1 will not be as accurate anymore as the people being affected by this treatment is not the same sample as one that has been recently blinded. A more accurate quality of life measure will be higher, perhaps closer to 0.9 depending on the proportion of those who have been blinded for a long time among those for whom the treatment is meant for.

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