Sudden fogging or blurring of vision usually indicates serious eye disease and needs to be investigated by an ophthalmologist promptly. Fogginess or loss of visual field spreading from one part like a curtain closing is classical (but not always seen) of a retinal detachment. Some other causes for sudden blurring or loss of vision are: vitreous hemorrhage, retinal arterial or vein occlusions, optic nerve swelling and bleeding at the centre of retina, usually these are limited to one of the eyes.

A more gradual reduction in visual capabilities is generally more common and can affect both eyes at the same time. The common causes are requirement of proper corrective glasses, cataract, capsular opacification, glaucoma, dry macular generation as well as inflammatory diseases of the eye – uveitis, vascultis, etc. Though not as urgent as sudden visual disturbances, these too do require examination by an eye doctor as early as possible.