THIS ALGORITHM IS DESIGNED FOR USE WITH THE DATA FROM THE 6 ITEMS OF THE VisQoL DIMENSION IN THE AQoL-7D INSTRUMENT

The VisQoL is a six item dimension (items 21, 22, 23, 24, 25 26) for measuring the quality of life associated with visual impairment.

The formula in Step 1 below was created to derive dimension index for the 7th dimension of the AQoL-7D utility instrument. The values derived from the formula should not be interpreted as utilities on a life-death scale for use in cost utility analyses.

*Variable names: For this algorithm, the variables in your questionnaire or database should be named

aqol21, aqol22, aqol23, aqol24, aqol25, aqol26

Raw Data entry: The first response in any item, the item best, is entered as ‘1’, the second as ‘2’, third as '3' and so on. 

*Missing Values: Note that missing data are represented by a blank or dot  and are handled by imputing values within each dimension. This algorithm allows for 2 missing values.  However, if more item responses in the  dimension are missing the observations will be dropped and there will not be a dimension score or an instrument score for the individual.

 

Step 1: Right click on this SPSS Syntax File or this STATA file and select ‘Save Target as...’ or 'Save link As...' Choose the location you want to save it, and save the file to your preferred directory.

Step 2:  Open the file in your program, you may have to change the extension from .txt to .sps (for SPSS) or .do (for STATA)  

Step 3: Select Run -> All
This will produce an output file containing the results of the algorithm and some descriptive statistics

Step 4: Finally, please remember that you will need to save the dataset to a new file or overwrite existing file to have the scores available for future use.

Note: If you are experiencing any problem in executing the algorithm please contact the AQoL team.

The multiplicative formula is described in Richardson, Iezzi, Peacock, Sinha, Khan, Misajon and Keefe (2012) ’Utility weights for the Vision-related Assessment of Quality of Life (AQoL) 7D instrument’ Opthalmic Epidemiology, 19:3, 172-182