This test, called refraction, involves placing different lenses before your eyes to check your eyesight from your own viewpoint. There may be a slight difference between the prescription that is estimated using the instruments and the prescription that you find most comfortable to wear. You will be asked to decide between a choice of two lenses or to say whether a lens makes what you see better or worse. Many people feel that they must make a choice.

However it is important that you tell your optometrist if you are unable to tell the difference as this means something to him as well. Many people worry about 'getting the answers wrong' at this stage - in fact there is no right or wrong as it is the range of answers rather than any particular one which the optometrist assesses.