Because fog vision screens are the true equivalent of seeing at a distance, the lens is unadjusted, there are no adjusting sets involved, and there are no eye position concerns, which means there are no side effects of fog vision screens.
The effect of fog vision therapy = the amount of training brought about by the efficacy of the action time, which needs to be long enough to produce a good enough effect, the effect is produced slowly and steadily, it will take 3 to 6 months to show the effect.