Depth perception is the ability of the visual cortex to calculate how far away an object is just by looking at it. Depth perception is a combination of accommodation and convergence that occurs when you try to focus on something. Problems with depth perception and resulting vertigo may occur when lenses are changed, because the relationship between accommodation and convergence changes. Wear your prescription lenses when driving or operating heavy machinery, and consult with your optometrist if you have problems with depth perception while wearing your prescription lenses. When changing your normalized or differential lenses, make gradual changes, and give your visual cortex time to adjust.