Blurred vision in one eye is a serious medical symptom and should always be evaluated by a physician. Blurred vision results from an inability of the optic nerve to process images as they are seen; it can be caused by a build-up of pressure within the eye or a clouding of the lens of the eye. Some cases of blurred vision in one eye are caused by an ocular migraine or diabetes; a headache with blurred vision, however, may be a symptom of a stroke and should be cause for an immediate examination by a medical professional.

Cataracts are the most common cause of blurred vision among the elderly. The lens of the eye becomes clouded from a breakdown of the proteins that form the lens. Objects become blurry and a halo may appear around lights. Some people report a loss in the intensity of colors and difficulty seeing at night as well.

Glaucoma is an eye disease caused by a build-up of pressure within the eye and can cause blurred vision in one eye. The pressure damages the ocular nerve resulting in visual changes. Physicians will usually recommend a series of eye drops to reduce the amount of fluid causing pressure in the eye. Sometimes laser treatment can be performed to release the fluid by creating new outflow channels for the vitreous fluid.

Headaches accompanied by visual changes are not unusual. Migraine sufferers typically report auras or floaters in their fields of vision prior to a migraine attack. Blurred vision in one eye can occur as part of a migraine phenomenon called an ocular migraine. The main symptom of an ocular migraine is changes in the vision of one eye that lasts for a few hours. Typically, there is no headache with an ocular migraine.

Diabetics are at a particular risk for vision problems due to uncontrolled blood sugar levels. Diabetic retinopathy can begin with blurred vision in one eye and floaters across the visual field. Additional fragile blood vessels can grow in the retina, distorting the images processed by the optic nerve. A build-up of scar tissue from the rupture of these small blood vessels can cause the retina to detach, possibly leading to blindness. Diabetic retinopathy often is treated by laser surgery in an outpatient setting; recognizing the symptoms early can save the vision of those affected by this disease.

Vision changes with a sudden headache may be a sign of a stroke as well. If the blurry vision happens at the same time as muscle weakness, tingling in the extremities, dizziness, or a sudden inability to articulate, immediate attention by medical personnel is critical. Blurred vision in one eye is always a matter for a medical attention, as it may be a sign of a serious illness.