Age-related eye changes are the most common cause of dark spots in the eyes, or floaters, though inflammation in the back of the eye, bleeding in the eye and a torn retina also cause the condition, notes Mayo Clinic. People who notice a sudden increase in the number of floaters, especially if accompanied by light flashes or loss of peripheral vision, should contact a medical professional immediately.
People with eye floaters may see dark spots that move when they move their eyes, that are more noticeable when the eyes look at a bright background or that may eventually drift out of their line of vision, notes Mayo Clinic. As people age, the vitreous of the eye partially liquefies and pulls away from the interior of the eye. As the vitreous gets smaller, it can clump together and block some of the light passing through the eye, causing floaters. Eye injuries and blood vessel problems can lead to bleeding into the vitreous, which also causes eye floaters.
If sagging vitreous pulls on the retina with enough force, it can tear the retina and cause eye floaters, states Mayo Clinic. People who suspect they have retinal tears should seek medical attention immediately, as they can cause retinal detachment, which can lead to permanent vision loss. Infections or inflammatory diseases may cause posterior uveitis, or an inflammation of the uvea in the eye, which can also cause eye floaters.