Floater disease is a vitreous opacity, while cataract is a lens opacity; these two conditions are not the same issue.

Vitreous opacities can be classified as physiological or pathological. Physiological vitreous opacities appear as moving objects in front of the eyes, which are less noticeable in the dark and more noticeable under bright light; cataracts gradually affect vision. Physiological vitreous opacities in floater disease generally do not affect vision, but pathological vitreous opacities do affect vision. An eye ultrasound shows severe vitreous opacities and retinal changes, whereas the cloudiness in the lens, namely cataracts, usually means the vitreous and retina are normal.