Vision Changes Caused by Stroke

A stroke can cause significant changes in vision. Most of the time, a stroke survivor experiences only one or, possibly, a few of these vision changes, but not all of them. This is because different regions of the brain work together to control vision. So, depending on the size and location of a stroke, it may or may not affect various aspects of vision. 

Learn more about the types of vision problems a stroke survivor may experience.

Visual Field Cut, or Loss of Peripheral Vision 

A visual field cut is a partial loss of vision. It can cause vision loss on the left or the right side, in the upper field of vision, in the lower field of vision, or in a combination of areas.

Our ability to see the world is dependent on the brain perceiving the world around us as if it were a four-wedge pie placed neatly together to make a whole pie. When a stroke causes homonymous hemianopsia, both eyes lose the ability to see the same "slices of pie." So, a visual field loss can result in both eyes being unable to see the left side or both eyes being unable to see the right side or both eyes being unable to see the upper right or the upper left sides. 

This symmetry of vision loss that occurs as a result of a stroke can be specifically described as left homonymous hemianopsia, right homonymous hemianopsia, right upper quadrant hemianopsia, and so forth. 

Homonymous hemianopsia can result when a stroke damages a region of the temporal lobe, parietal lobe, or occipital lobe. The specific location of the stroke determines exactly the area of vision loss. Damage to the right side of the brain causes loss of left-sided vision, while damage to the left side of the brain causes right-sided vision loss.

Visual Neglect or Visual Extinction

Visual neglect is somewhat different from homonymous hemianopsia. Visual neglect is a condition in which stroke survivors have a deficit in attention to and awareness of one side of the body.

This neglect of one side may be absolute (visual neglect) or it may only happen when another object in the "normal" side competes for attention (visual extinction).

Visual neglect and visual extinction more commonly occur when a stroke affects the right parietal lobe.

Double Vision or Blurred Vision 

Double vision, or diplopia, from a stroke weakens eye muscles in such a way that one eye cannot perfectly align with the other eye, giving the perception of two objects when there is only one.

Diplopia can be present all of the time, or it can be present only when you are looking in a certain direction, for example when you move your eyes to the left, to the right, or up or down. Often, diplopia makes your vision appear to be fuzzy or unclear, rather than distinctly double, as the two images may overlap, appearing blurred. 

Most of the time, diplopia is caused by a stroke of the brain stem or the cerebellum, although sometimes cortical and subcortical strokes can also produce diplopia.

Loss of Vision

A stroke can cause complete vision loss in one eye and, rarely, in both eyes. Complete loss of vision of one eye usually occurs as a result of a blockage of one of the arteries supplying blood flow to the eye, the ophthalmic artery or its branch called the retinal artery. 

Some stroke survivors can lose vision in both eyes after a stroke affecting both occipital lobes, a condition known as cortical blindness, which means that the stroke survivor’s eyes react to light (the pupils get smaller in response to light) as if he or she can still see. In cortical blindness, however, a stroke survivor cannot see because the brain is unable to perceive the visual message.

Sometimes, people with loss of vision are not aware that they can't see and they behave as if they can. This condition is called Anton’s syndrome and is usually caused by strokes involving the primary areas of vision in the occipital lobes. 

Visual Hallucinations 

Visual hallucinations may occur after a stroke. Hallucinations are experiences or perceptions of things that are not real.

A condition called Charles Bonnet syndrome is characterized by the occurrence of visual hallucinations in stroke survivors who are visually impaired due to an eye or brain condition involving the visual pathways.

Such conditions include:

• Cataracts
• Glaucoma
• Macular degeneration
• Stroke
• Brain tumor
• Head trauma

Stroke survivors who have Charles Bonnet syndrome generally are aware that the objects they see are not real.

The disruption in the visual pathway in the brain results in false complex visual messages being delivered to the vision centers in the brain. A stroke in any of the vision areas of the brain can cause Charles Bonnet syndrome, but most often, it is caused by a stroke of one or both occipital lobes.

Achromatopsia, or Loss of Color Vision

A rare condition called achromatopsia is the loss of color vision, resulting in objects appearing to be black, white, or gray. Caused by the combination of damage to several parts of the brain or by a genetic defect, achromatopsia is one of the rarest visual effects of a stroke.

Amaurosis Fugax 

Amaurosis fugax is a visual change associated with a transient ischemic attack (TIA), which is a temporary, reversible stroke. The classic symptoms of amaurosis fugax include a sense that a dark shade or black curtain is coming down vertically into the field of vision of one eye. Sometimes amaurosis fugax is described as sudden vision loss or partial vision loss.

The key feature of amaurosis fugax is that it improves fairly quickly. This is because it is caused by a temporary interruption of blood flow to the eye, which is a TIA, considered a prestroke warning. Most people who complain of symptoms that sound like amaurosis fugax are subsequently diagnosed with internal carotid artery disease. When the cause of a TIA is identified and medically treated, a stroke can be avoided.

Vision Changes Not Associated with Stroke 

There are several common vision problems that are caused by eye problems, heredity or other diseases, but not a stroke, including:

• Floaters: If you see occasional "floating" spots, this is usually a sign of aging, or sometimes a sign of diabetic eye disease, which may cause serious vision changes if left untreated. If floaters persist, you should get medical attention to prevent further complications.
• Seeing halos around lights: A cataract, which is often the result of normal aging, diabetes or smoking, causes a sense that you are looking through a cloudy or frosty glass. Cataracts can be effectively and safely treated.
• Nearsightedness or farsightedness: The common problems of nearsightedness and farsightedness are a result of imperfect focusing of the eyes. People who are nearsighted have difficulty focusing on faraway objects, while people who are farsighted have difficulty focusing at all ranges. These are hereditary problems or a result of normal aging, but not a stroke.
• Triple vision: There is no real biological reason for triple vision. People who claim to see multiple objects may be under the influence of medications or drugs or experiencing a psychiatric issue. 
• Red-green color blindness: Red-green color blindness is different from achromatopsia, when a person can't see color. Red-green color blindness is a hereditary condition caused by a genetic defect.

A Word From Verywell

One of our most important senses is the sense of vision. Vision requires a complex interaction between the eyes and the brain. A stroke can cause several changes in vision, depending on the size of the stroke, and which region of the brain is affected. Rehabilitation for vision loss is a long process that requires a great deal of patience and persistence.