Vision

Understanding vision changes after a stroke

Vision is one of our most important senses. More than two-thirds of all sensory processing in the body is directly affected by information coming from our eyes. The input we receive from our eyes travels throughout both sides of our brain, interpreting the information we see to make sense of it. Vision guides motor function and movement, provides feedback to improve postural awareness, and helps us to orient our body in space and to identify sides of the body.

Visual processing is the act of delivering information to the brain for the purposes of attention, concentration, and cognitive processing, allowing us to participate in tasks such as reading, writing, cooking, and driving.

Following a stroke, it is important to address vision and visual processing dysfunction to reduce complications, maximize the rehabilitation process, and support each person with a brain injury in their goals to return to independent functioning.

How vision works

  • Vision is produced by input entering two eyes. Each eye is controlled by a network of 6 muscles, with each muscle controlled by a different nerve in the brain (cranial nerves) to produce a specific eye movement. These muscles allow the eye to move up, down, left and right, and to rotate toward and away from the nose.
  • When the muscles of each eye work together to coordinate the movement of both eyes, the eyes will be aligned, move in all directions, and produce a single image.

Types of vision deficits

  • Double vision: When the muscles are not working due to weakness or injury, many deficits can result in either or both eyes. These include misalignment, decreased coordination, and decreased amount and speed of movement. When someone is experiencing these deficits, they typically complain of double vision, also known as diplopia.
  • Misalignment: This type of eye movement dysfunction, also known as strabismus, prevents the eyes from aligning with each other. It’s usually caused by result of trauma or increased pressure in the brain. The eye may turn in, out, or up, with the direction depending on which nerve in the brain has been affected. The eye turn may involve weakness or paralysis of the eye muscle. Symptoms include misalignment, complaints of double or blurry vision, complaints of floating images, and closing or covering of one eye. The condition can cause poor coordination and depth perception and difficulty walking on changing surfaces.
  • Convergence: Issues related to an eye’s ability to converge and diverge, also known as an accommodative dysfunction, is common after brain injury or stroke. Convergence occurs when the eyes simultaneously turn toward each other in order to see an image clearly when close up, while divergence occurs when the eyes turn away from each other to see images clearly at a distance. When an individual’s eyes look at near objects and then at distant objects, the eyes must make necessary adjustments in order to focus on both the near and far objects and to see these objects clearly, a process called accommodation. Symptoms include complaints of blurred vision while reading, eye strain and discomfort, headaches, fatigue or sleepiness, and eyes drifting out with near vision but working well at a distance. The affected person will tire easily, be unable to focus on near objects and when shifting between near and far vision, require frequent rest breaks with tasks requiring sustained attention, and experience frustration and poor concentration or loss of comprehension over time.
  • Uncontrolled movements: This type of eye movement dysfunction, also known as nystagmus, can occur following a brain injury. The cause of nystagmus can at times be unknown and difficult to treat. It appears as an involuntary, rhythmical, and repeated movement of one or both eyes in a circular or horizontal pattern. It can occur in any or all fields of gaze. Different types of nystagmus that can result following a head injury may be related to vision loss, control of muscle function, inner ear problems, and medication.
  • Visual acuity: The measure of the eye’s ability to see small detail clearly, both near and far, is recorded with a number on top (which is the testing distance) and a number on bottom (the distance that the letters/symbols are being viewed). Normal visual acuity is commonly called 20/20 vision, meaning that an individual can see clearly at 20 feet what should normally be seen at 20 feet. Symptoms include squinting, complaints of too-small type, and of blurry vision. It can result in decreased facial recognition and difficulty with tasks such as reading and finding one’s way.
  • Visual fields: The eye’s visual field is the space you see when you’re looking out in to the world. An individual can be looking at an object, but can also see the space around the object’s surroundings, known as the peripheral field. There are four visual fields for each eye: superior (up), inferior (down), temporal (by the ear), and nasal (by the nose). Deficits may result in vision missing in the outer half of each eye, on one side, or in one direction. Symptoms include changes in gaze preference, head turning or tilting to one side, running into things, complaints of seeing blackness or not seeing, and missing items during self-care tasks. It can result in poor hygiene, unsafe mobility, decreased body awareness, poor navigation, and an increased need for caregiver assistance.
  • Visual perception: The ability to interpret the surrounding environment by processing visual information may be impacted by a head injury, directly affecting the person’s function and independence. Deficits may affect a range of health aspects including the person’s body image and regulation, awareness and recognition of body parts, and spatial relations. Symptoms include difficulty sequencing steps during activities, difficulty writing and drawing, and difficulty routing the environment or finding something in a crowded area. It can result in decreased independence and safety awareness and confusion about left and right or likes and differences.

How eye care professionals can help

If you feel that the person recovering from brain injury would benefit from additional vision care services, please discuss the different options available with their primary care physician.

Neuro-Ophthalmologist (MD)

  • Specializes in the diagnosis and treatment of diseases and disorders that affect vision and perception as a result of neurological damage
  • Same education as ophthalmologist (MD)

Ophthalmologist (MD or DO)

  • Qualified to deliver total eye care, meaning vision services, eye examinations, medical and surgical eye care, diagnosis and treatment of disease, and visual complications that are caused by other conditions
  • Training emphasizes eye disease and surgery
  • Specialize in the medical and surgical care of the eyes and visual system, and also the prevention of eye disease and injury
  • Doctor of medicine (MD) or doctor of osteopathy (DO) degree
  • Education includes four years of pre-medical undergraduate education, four years of medical school, one year of internship, and three or more years of specialized medical and surgical training in eye care.

Optometrist with Fellow from College of Vision & Development (FCOVD)

  • Same education as the Optometrist (OD), with additional training in vision therapy and rehabilitation
  • COVD offers optometrists and vision therapists the opportunity to become certified in vision development and vision therapy. The Board certification process is administered by the International Examination and Certification Board of the College of Optometrists in Vision Development.

Optometrist (OD)

  • Trained to examine, diagnose, treat, and manage some diseases and disorders of the eye and visual system
  • Can determine the presence of vision problems and visual acuity, prescribe eyeglasses and contact lenses, prescribe eye exercises, low vision aids, and vision therapy, and prescribe medications to treat eye diseases.
  • Do not perform eye surgery and are not trained to care for and manage all diseases and disorders of the eyes
  • Education includes pre-professional undergraduate education and four years of professional education in optometry. Some optometrists may complete a one-year optional residency in a specialized area, such as neuro or behavioral. They do not  attend medical school.

Optician

  • Assist optometrists and ophthalmologists in providing complete patient care before, during, and after exams, procedures, and surgeries
  • Able to analyze and interpret eye prescriptions, determine the lenses that best meet a person’s needs, oversee ordering and verification of eye-related products from start to finish, and dispense, replace, adjust, repair, and reproduce previously ordered items
  • Can help to fit eyeglasses and contact lenses, following prescriptions from ophthalmologists and optometrists
  • Help customers decide which eyeglass frames or contact lenses to buy
  • Do not test vision or examine eyes for disorders/diseases
  • Typically complete a two-year technical degree
You're on Shepherd Center's patient education website. For our hospital's main website, please visit shepherd.org.