Cerebral Visual Impairment (CVI) was the topic of the Eye & Ear Foundation’s first webinar of 2024.
Dr. Ken Nischal, MD, FAAP, FRCOphth, Director of Pediatric Ophthalmology, Strabismus, & Adult Motility, Director of Pediatric Program Development at UPMC Children’s Hospital of Pittsburgh, and Executive Vice Chair and Professor of Ophthalmology at the University of Pittsburgh School of Medicine and one of the pioneers of pediatric corneal transplants, first talked about brain anatomy. The different lobes of the brain (parietal, frontal, temporal, occipital) are all part of the conversation when it comes to CVI.
The Brain
Vision is not just the eyes, Dr. Nischal said. The eyes capture an image that the brain then interprets, remembers/identifies, and contextualizes. The brain is responsible for decision acquisition and execution, as well as consequences.
The parietal lobe is responsible for visually guided behavior, while the temporal lobe deals with object perception and recognition. The dorsal stream runs between the occipital lobes and posterior parietal lobes, subconsciously appraising the whole visual scene. This area computes the location of components and vacillates visual guidance of movement. The ventral stream connects the occipital lobes to the temporal lobes, which contains the brain’s “visual library.” Information transmitted here allows for recognition and visual memory of what is being looked at, as well as recognition of faces.
What is CVI?
This term can mean cortical visual impairment or cerebral visual impairment depending on who is using it. Perhaps a newer term, brain based visual impairment is best, because it imparts the fact that it can involve any visual processing part of the brain, Dr. Nischal said. Even though for different folks, CVI means different things, for the time being, CVI may be the best moniker.
CVI is a neurological condition that affects the visual processing centers in the brain. It is characterized by visual impairments or difficulties in interpreting visual information despite the absence of significant damage to the eyes themselves. It is often seen in individuals who have had brain injuries, developmental disorders, or other neurological conditions that affect the brain’s ability to process visual info effectively.
Symptoms of CVI
Children with CVI do not appear to be:
- Responding to the things they see
- Seeing certain parts of what is in front of them, like busy moving scenes
- Recognizing faces and objects
- Recognizing things in cluttered spaces
- Able to reach for something while they’re looking at it
- Able to understand what they’re looking at
Parents may also notice that their child with CVI:
- Reacts slowly to visual cues
- Prefers to look at things that are moving
- Prefers to look at things in a certain part of their vision, like with their peripheral (side) vision
- Tend to stare at light (like lamps or the sun) or are sensitive to light
- Have other disabilities or health problems, including developmental disabilities, cerebral palsy, or epilepsy
Causes of CVI
The most common cause of CVI is perinatal or postnatal hypoxia (lack of oxygen) in preterm or term children. Other causes include:
- Hydrocephalus (when fluid builds up in the brain)
- Infections that reach the brain
- Head injury
- In utero drug exposure
- Structural brain abnormalities
- Seizures
- Metabolic conditions
- Certain genetic conditions
In the U.S. and other developed countries, CVI is the leading diagnosis of visual impairment in children aged 0-3. Despite this, there are no agreed clinical guidelines for its investigation and diagnosis.
Buncher Foundation Funded Research into CVI at Children’s Hospital of Pittsburgh (CHP)
Preeti Patil, Beth Ramella, Alki Liasis, Ken K. Nischal, and José-Alain Sahel all looked into what assessments are currently used to investigate and diagnose CVI in children.
Dr. Nischal discussed a study conducted by McConnell et al., in which of 6454 identified articles, 45 met inclusion criteria. Ten categories of assessment utilized within included articles were identified.
When it comes to diagnostic criteria in defining CVI, the most commonly reported approach was one of exclusion. In other words, CVI was diagnosed when visual dysfunction could not be attributed to abnormalities detected in the anterior visual pathway. The most commonly documented presentation used to form a diagnosis is based on a child presenting with visual difficulties which are unexplained by results of vision assessment/ophthalmological examination.
However, a “diagnosis of exclusion” approach may allow for diagnostic overshadowing, Dr. Nischal said. Visual deficits recorded may be attributed to co-existing neurological impairments affecting speech, behavior, cognition, or movement rather than CVI.
Neuroimaging was the second most commonly reported method used to diagnose CVI in children. In most articles, this was in conjunction with visual difficulties that could not be explained by the results of vision assessment/ophthalmological examination.
The majority used visual evoked potentials (VEPs) to evaluate the integrity of the visual pathway from the retina to the striate cortex. Thirty percent of the papers used clinical electrophysiology as a criteria.
The study’s goal was to develop a deep phenotype and then correlate that with assessments, electrophysiology, visual function, and MRI. To get a diagnosis, the group found, involves detailed history taking, caregiver questionnaires that assess various aspects of visual functioning, specific questions directed at visual behavior differences, an ophthalmic exam, visual field assessment, electrophysiology, and neuroimaging.
VEPs do not detect CVI, Dr. Nischal cautioned.
More Info on the Study
Dr. Preeti Patil, MD, pediatric ophthalmologist and neuro-ophthalmologist at UPMC Children’s Hospital of Pittsburgh Pediatric Ophthalmology Service and an Associate Professor of Ophthalmology at the University of Pittsburgh School of Medicine who also runs a nystagmus clinic at CHP, provided more information on the study funded by the Buncher Foundation.
The study consisted of 51 patients, aged 1-18 years, with the majority under the age of five. All patients underwent a complete eye exam that examined the structure of the eye. They also had an ocular motility exam, which looks for nystagmus (eyes that shake) and strabismus (eye misalignment). Cycloplegic reflection for glasses was used to detect any associated far/near sightedness or astigmatism.
More than half of the patients needed glasses or management of lazy eye (amblyopia). Seventeen patients had nystagmus, and 29 had strabismus.
About half of the kids had normal optic nerves, but the other half had damaged optic nerves.
All patients underwent VEP, measuring the electrical signal the visual cortex generates in response to visual stimulation. Abnormal results were found in 65% of the patients. These patients may have other issues as well.
All patients had an MRI – imaging of the brain. Results were varied. Three had a normal MRI. Some were initially normal and then had progressive changes. Abnormal MRIs were due to a wide range of things, like strokes, hypoxic damage, or hydrocephalus. Volume loss was seen in the affected areas in some MRIs.
A behavioral assessment was conducted on patients. This included a functional vision assessment by a trained and experienced teacher for the visually impaired (TVI), and a caregiver questionnaire designed to generate strategies (Insight questionnaire).
Functional Assessment
The Insight inventory by Dr. Gordon Dutton is composed of 52 questions that refer to the visual, perceptual, and visual motor difficulties across six domains: visual search, visual fields, visual attention, perception and movement, visual guidance of movement, and recognition and navigation. The caregiver rates whether or how the question is present in their life. Tailored habilitation strategies are then created and shared with the family, caregiver, and school.
The CVI Range Assessment by Christine Roman-Lanzy uses two ratings to obtain a score determining the degree of CVI impact. One rating determines the extent to which CVI interferes with the child’s functional vision. The second rating examines each characteristic (color, movement, visual fields, latency, visual complexity, light, distance viewing, reflexes, novelty, and visual motor match) and the effect on functional vision. A score of 0-10 is produced and guidelines to interventions for learning are created and shared with the family, caregiver, and educational team. This is primarily designed more as an educational or learning tool to help children function better in their learning environment, Dr. Patil said.
Adaptations and Strategies
Following the assessment, individualized interventions are created based on the student’s use of vision, strengths, needs, interests, and routines at home/school. Examples include:
- Use of black backgrounds to eliminate visually complex environments
- Materials chosen based on the child’s preferred color and presented in their best visual field
- Materials and targets presented on a light box or backlit device
Adaptations include the use of visually clean fonts. Other adaptions:
- Print work (such as worksheets) adapted to include less on a page or by covering some of the visual information by using a typoscope or line marker
- Adequate spacing between words and lines of print
- Learning materials presented on a backlit device such as a tablet or computer screen
- Books presented upright on a reading stand
Results
The group discovered an excellent correlation between the Insight questionnaire and the CVI range. “To our knowledge, this is the first time that these two types of tools have been used in the same patient,” Dr. Patil said.
Dr. Patil then shared three case studies to demonstrate this. Despite many differences among these cases, they all had CVI.
The group conducted phenotyping (description of clinical characteristics) and are further analyzing data to come up with a correlation between different features (such as MRI features and behavior) and came up with a classification system.
Future directions will hopefully answer questions like:
- Are there specific areas of the brain that may always be involved regardless of type of CVI?
- Are coping strategies that are self-generated as effective as those suggested after analysis by a trained TVI?
- Are there specific functions that are affected depending upon which area of the brain seems most affected?
“Some of these questions we are studying as part of the study,” Dr. Patil said. “Still, there are so many more questions that we need answers to.”