What is the difference between the ADD value (seen in the VisionCheck app) and my reader number?

The ADD value given to you when you complete your EyeQue Refraction Measurement (ERM) is an ADD based on your age. It is based on a step chart that has been in use for many years. The ADD value calculated with the MyReaderNumber app is based on the measured distance and our formula to create an ADD value that is customized to your needs. It does take into account your age when making this calculation so make sure to enter your proper birth year.