Originally Posted by
DocInChina
Ilahn,
With all due respect, if you wanted to conduct a double blind study it would require that you have no knowledge about which progressives (brands, traditional surfaced and free form) that you were wearing. The frames should be identical in everyway which you mentioned you already did) and the lenses or frames should be labeled A, B, C directly on the frame. In the event the frames are put into the wrong case, you would still know which was Frame A, B, C, etc.
The better method of conducting this would be for you to choose a group of test subjects and record their sex, age, education and previous progressive wearing history and ask if they know which brand they are currently wearing. Actually there are more questions to add to this which would be important for statistical analysis.
The person taking the measurements should not be the same person to glaze the lenses. The person doing the dispensing should not be the person who glazed the lenses. If you then have 4-6 different lens brands/designs you would then create a test group of at least 30 people split between men and women. Then you would create a questionnaire asking the persons preference from best to worst and asking specific questions to ascertain why they preferred one set of glasses over the other. You could then create control group where all the glasses are one type of progressive but still giving them 4-6 frames labeled A, B, etc and asking them which performed best, etc, the same as you did for the non-control group.
For the purpose of analyzing test results, it would not be considered a double blind study if you are the tester and testee for a study no matter how impartial you considered yourself. The data would be considered contaminated.
We are currently conducting a double blind study (not ophthalmic related) and we had to go over all the testing details to insure the study would not be contaminated rendering the test results useless for our purposes.
Eric
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