After Stroke—I Can See, But I Can’t “See”

By James Wymore, M.D.

The visual system is tremendously complex.  Even the simplest ocular tasks are performed via a series of neurologic connections integrating the eyes and the brain.  There is a constant flow of information about a person’s environment while he or she is awake, allowing one to move within and manipulate that environment.

Strokes, or cerebrovascular accidents (CVA), are a relatively frequent occurrence.  If blood supply is severely restricted or completely cut off to a certain area of the brain, that tissue dies, completing a stroke.  Depending on the area affected, different symptoms or signs result.

When a stroke damages parts of the brain coordinating visual activities, it highlights functions of the visual system that previously were taken for granted.  It emphasizes the importance of these abilities by destroying them.  The symptoms can be subtle or obvious, and at times are present even with 20/20 vision.

A hemianopia from a stroke of one of the occipital lobes, the visual center of the brain, is a good example.  Hemianopia is a loss of one half of one’s visual field (peripheral vision).  A person is unable to see either to the right side in both eyes, or to the left side in both eyes.  If the right side of the field is missing, it is very difficult to follow sentences from left to right in the usual reading pattern.  If the left side is missing, it is difficult to return to the next lower line after finishing a line.  Thus, a person may possess good central vision and perform well on an eye chart, but struggle to read a newspaper.

A stroke in just the “right” location may cause a phenomenon called pure word blindness.  The person can’t read, but he or she is able to spell and write.  Colors can’t be named, but can be matched, and objects can be colored appropriately.  Another area of the brain damaged by stroke may prevent recognition or naming of objects, in spite of the person’s continued ability to recognize the same objects by touch.

Palinopsia is a condition in which a person visualizes multiple, different images superimposed upon each other.  Previously seen figures may be played back up to several hours later, causing significant confusion.  This symptom results from temporal-parietal-occipital lobe lesions.

Disordered processing in the occipital lobes after a CVA may result in alterations in our perceptions.  Images may be distorted (metamorphopsia) and the position and size of objects, as seen by the faulty nervous tissue, may be unreliable.

Midbrain infarctions may lead to an obscure syndrome of peduncular hallucinosis.  In this entity the stroke causes the person to experience colored lights or colored scenes, often including figures that seem to be moving about.

These are a few examples of problems people might encounter following strokes.  They may be able to read the 20/20 line on the doctor’s chart, but their visual system is not functioning properly and is giving them problems.  Dealing with the symptoms is frustrating.  The frustration may be lessened by understanding what has happened and having a physician confirm that the symptoms are a result of their disease process.

Eye Surgeons Associates located in Bettendorf, Muscatine, Rock Island, Silvis and Geneseo, provides comprehensive eye care for the entire family, for a lifetime. Our medical doctors are fully fellowship trained in their specialties and board certified. For more information visit us online at www.esaeyecare.com. Dr. Wymore graduated with a Bachelor of Science from the University of Iowa where he also received his medical degree. He completed his internship at the University of Oklahoma and residency in ophthalmology at the University of Missouri. Dr. Wymore’s clinical interests are in general ophthalmology.