As a rule of thumb, a difference in magnification over what percentage from eye to eye is usually problematic for the wearer?

A difference in magnification of 4% from eye to eye is typically considered problematic for the wearer. This threshold is based on the fact that when magnification varies significantly between the two eyes, it can lead to issues such as visual discomfort, difficulty in focusing, or even binocular rivalry. When the magnification difference is above this percentage, it may cause the brain to struggle to merge the images adequately, which can adversely affect depth perception and overall visual clarity.

Understanding that a 4% difference aligns with the limits of how much visual variability the human brain can reconcile helps in the design and fitting of corrective lenses. Anything above this threshold can lead to difficulties, making it essential to maintain magnification differences within a comfortable range to ensure visual harmony between both eyes.