You may well wonder if the traditional vision test, i.e., subjective refraction, is necessary at all, if the results can change based on conditions. The answer is yes. The eye care professional must be able to record your personal reaction to the various lenses he or she inserts in front of your eyes. Just as importantly, subjective refraction also tests how your eyes interact and how they will see with your new glasses.
However, there are ophthalmic instruments such as the ZEISS i.Profiler®plus which can be used to perform objective refraction beforehand. It uses wavefront technology to analyze the vision profile of each eye on the basis of 1,500 measuring points and generates a "map" of the eyes’ retinas. All you need to do is look into the i.Profiler® plus ; the scan usually takes a minute or two. This is a preparatory measurement, the results of which are then refined by the eye care professional in the subsequent subjective refraction procedure.
And that is not all: as the i.Profiler® plus measures visual performance with a contracted pupil (in bright light) and a dilated pupil (in poor light or at night), it is possible to determine whether your night vision is poorer than your daytime vision. The eye care professional can then use this information to optimize the lenses appropriately. A major benefit of this procedure is that the time required for the vision test may be reduced.