Cerebral Palsy is a non-progressive motor disorder that is caused by damage to the neurologic pathway in the brain. This damage is generally caused by an ischemic event (lack of oxygen) during development but could also be caused by trauma or infection during the first years of life. Individuals with cerebral palsy have varying degrees of motor disabilities and cognitive disabilities. Cerebral palsy is the most common disability in children.
Cerebral Palsy has several effects on the visual system, which include:
Cortical Visual Impairment (60-70% of patients with cerebral palsy)
- An ischemic event (lack of oxygen) during development can cause changes within the brain that result in reduced clarity of vision. Unfortunately glasses, contact lenses, or surgery cannot correct this reduced vision. It is therefore important to identify cortical visual impairment, as the management is much different than treating blurry vision with glasses. Our doctors are able to quantify the vision loss due to cortical visual impairment and make appropriate recommendations for a modified learning environment.
- Changes to the optic nerve, called optic atrophy, results in reduced vision. As reduced vision due to optic atrophy cannot be corrected with glasses or contacts, it is important to identify so that appropriate modifications to learning environments can be made.
Reduced contrast sensitivity (ability to see shades of gray)
- It may surprise you to know that contrast sensitivity is one of the primary visual skills we use to move through the world. Even an individual who can see 20/20 will have troubles with mobility if they have reduced contrast sensitivity. Even more surprising is that the vast majority of eye doctors do not even assess contrast sensitivity or have the equipment to do so. At Artisan Optics we have the equipment to assess contrast sensitivity on most individuals including toddlers or even non-verbal individuals and do so during every Specialized Eye Examination.
- As cerebral palsy is a motor disorder, it is especially important to know any visual limitation to mobility as moving through the world is already a difficult task. Any visual modifications to a person’s surroundings that address visual difficulties will have a profound effect on mobility.
Reduced visual acuity
- For individuals with cerebral palsy, vision can be reduced for a number of reasons. Uncorrected prescriptions, reduced eye focusing abilities, cortical visual impairment, and optic atrophy are just a few of the causes of this reduced vision. It is important that our doctor identify the exact cause of the reduced vision so that the most appropriate management plan can be initiated.
Reduced visual field (peripheral vision)
- Cerebral palsy is a motor disorder, so often times it is assumed that mobility difficulties are not due to ocular changes. However, if a person has constrictions in their visual field (or blind spots) it will be even more difficult for them to move through the world.
- Identifying visual field defects allows the person, their family, and their care team to better understand how they see their surroundings. Our doctors are able to make recommendations for classroom modifications, home environment modifications, and make suggestions that allow occupational and physical therapy to be of most benefit to the person.
Abnormal stereopsis (depth perception)
- Depth perception is extremely important when moving through the world. This is especially true for those with motor difficulties. Absent or unstable depth perception can compound any mobility difficulties due to cerebral palsy, contrast sensitivity, reduced visual acuity, or cortical visual impairment.
Optokinetic nystagmus (eyes appear to jiggle from side to side)
- Nystagmus is a rhythmic back and forth movement of the eyes. Some forms of nystagmus are due to underlying pathology while others are considered physiologic and of no concern. Our doctors are used to working with patients who have nystagmus and are able to differentiate the different cause of nystagmus.
Fixation abnormalities (ability to keep eyes focused on a target)
- Poor ability to keep one’s eyes “locked on” to a target can create many difficulties. In school, fixation abnormalities will make it extremely difficult to take in visual information.
- Fixation abnormalities will make it difficult to copy information from the board, read, or complete other classroom assignments.
Saccadic abnormalities (ability to jump from target to target)
- Saccades are coordinated jumps of the eyes (think of shifting your attention quickly from the television to your phone when someone calls. These eye jumps are essential for most visual tasks. In school, saccades allow a person to copy information from the board and read efficiently. People with saccadic abnormalities will notice that they often skip lines or re-read lines of text.
Pursuit abnormalities (ability to smoothly follow a target)
- Pursuits are smooth eye tracking movements. We use pursuits when following slow moving objects. Smooth eye movements are necessary to be a smooth and fluid reader.
- Strabismus, commonly referred to as "crossed" or "wandering eyes", occurs when one or both eyes turns in or out, up or down. The condition is caused by the brain's inability to coordinate both eyes simultaneously. The brain is the master control center of vision, and somewhere early in a child's vision development, the brain failed to develop "binocularity," or the ability to use both eyes at the same time. It is important that strabismus receive prompt treatment. Children do not outgrow crossed eyes, and the condition can worsen over time.
- Because the brain has not learned to align the eyes and use them together, each eye aims independently of the other. In other words, both eyes do not point at the same place at the same time. When each eye is looking at a different place, the brain receives two different "pictures". This would normally result in double vision. However, these children's brains learn to protect themselves from seeing double by suppressing, or "turning off" the crossed eye. The brain refuses to receive the visual input from the turned eye; children with a crossed or wandering eye only see out of one eye at a time.
- There are multiple treatment options for the treatment of strabismus. Some of these approaches are designed to physically reduced the magnitude of the eye turn so that it is less noticeable (even if the person continues to see double or suppress an eye), while others are designed to both improve the appearance of the eye turn and improve the binocular vision abilities; allowing for clear, comfortable, three-dimensional, vision with both eyes. Our residency-trained doctors can discuss all treatment options for strabismus and help you decide which approach is best.
Visual perceptual disorders
- Taking in clear visual information is just the first step in the visual process. Once the eyes have received visual information the brain must then interpret it. This visual process within the brain is called “visual perception” and allows us to make sense of visual information.
- Visual perception allows us to know that an “A” is an “A” if it is written very large on the board, small on a piece of paper, or as part of a word.
- Visual perception allows us to know that a chair is still a chair even if it is knocked over or viewed from a different angle.
- Visual perception allows us to pull valuable information out from a crowded background, such as when working on one problem within a worksheet.
- These are just a few examples of vision perception, but you can already see how important it is that we process visual information quickly and effectively. Visual perceptual deficits make learning extremely difficult and should be identified at an early age.
Poor Accommodation (difficulty focusing at near)
- Reduced eye focusing abilities make it very difficult to maintain clarity while performing near tasks, such as reading or computer work. This can lead to blurred vision, headaches, eyestrain, fatigue with near work, reduced reading fluency (skipped lines, re-reading of lines), and can affect performance in school.
- Eye focusing is especially important for people who use workspaces or communication devices within arm’s length. Many doctors only assess visual acuity at distance, but it is also important to assess near visual acuity if most visual material is presented at near. Knowing how well a person sees at near can help in the development of alternative communication systems.
As much as 80% of classroom information is taken in through the visual system. It is important the every child with cerebral palsy be examined by a residency-trained pediatric optometrist who has both the knowledge and experience working with patients who have cerebral palsy.
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