Disease, injury and degeneration can result in loss of eyesight. In children, the most frequent cause of vision loss is trauma to the eye or a case of amblyopia (lazy eye), whereas aging eyes gradually lose the ability to focus. Aside from those circumstances, major causes of adult blindness include cataract, glaucoma, diabetic retinopathy and retinal detachment.
A person with cataracts gradually loses transparency in the lens in the eye, making the eye appear cloudy. This condition may follow injury, stem from an infection or occur in aging eyes.
Glaucoma causes abnormally high pressure inside the eye, which ultimately damages the optic nerve. The pattern of progressive damage usually begins with a loss of peripheral vision.
Diabetic retinopathy is a progressive disease caused by diabetes where blood vessels in the retina swell and leak fluid. Unfortunately, retinopathy does not cause noticeable symptoms until significant damage has occurred. For this reason, ophthalmologists should examine diabetics' eyes regularly.
Retinal detachment happens when the retina is separated from the supportive layers at the base of the eye. Flashing lights or floaters are often the first sign of a retinal tear that precedes detachment. If you see a shadow and not floaters, this could mean the detachment has already occurred.