Cerebral visual impairment: A growing concern in pediatric vision loss

(Image Credit: AdobeStock/Matthieu)

Cerebral visual impairment (CVI) is a disorder caused by damage to the parts of the brain that process vision. It’s most common in infants and young children, but can continue into adulthood.

A child with CVI has vision problems that are caused by their brain that can’t be explained by a problem with their eyes. Normally, the eyes send electrical signals to the brain, and the brain turns those signals into the images you see. If you have CVI, your brain has trouble processing and understanding these signals.

CVI is a leading cause of vision loss among kids in the United States. For some children with CVI, vision may improve over time, but everybody is different. If your child has CVI, make sure that they get early intervention and therapy, educational support, and other special services to help them develop and learn.

Lotfi Merabet, OD, PhD, MPH, Massachusetts Eye and Ear, Harvard Medical School, recently served as co-chairman of a National Eye Institute initiative to promote research in CVI. During a conversation with Ophthalmology Times, he noted 3 main objectives for the recent NEI workshop.

“The first is to raise awareness for the condition of cerebral/cortical visual impairment of CVI. Second is to establish a series of definitions and diagnostic criteria that we can use for the care of individuals with CVI,” he said. “The third main initiative would be to establish a national registry that will be important for identifying children or individuals with CVI and characterizing their clinical profile, the diagnostic criteria that was used, and follow these individuals over time to get a sense of the natural history of the condition as well.”

Shefa Gordon, PhD, associate director for Science Policy and Legislation at the National Eye Institute, detailed how the NEI incorporated CVI into its strategic plan, and the steps taken to start to achieve those goals. He noted in the NEI Strategic Plan, NEI issued an RFI for topics of interest.

“The CVI community organized a concerted response, flooding the inbox comprising two-thirds of the 252 individual responses,” Gordon said. “Based on input from scientific planning panels, particularly in the areas of neuroscience and rehabilitation/quality of life, NEI identified CVI as a major research gap and outlined research opportunities in the Strategic Plan released in 2021.”¹

Gordon noted there were 3 that emerged, including lack of provider awareness/training, developing diagnostics, and development of effective rehabilitation/interventions.

“CVI was featured prominently in the Biology and Neuroscience of Vision, Data Science, and Individual Quality of Life Areas of Emphasis in the Strategic Plan, demonstrating the need for research on CVI that encompasses everything from basic understanding of CVI development to assessment of therapeutic interventions,” Gordon added.²

Recognizing that CVI diagnosis and care requires multidisciplinary coordination, NEI partnered with the National Institute of Neurological Disorders and Stroke (NINDS) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) to create a CVI Working Group and hosted the NIH CVI Workshop: Roadmap to Consensus and Building Awareness.

“The hybrid workshop was videocast—invited participants included ophthalmologists, optometrists, pediatricians, neurologists, research scientists, individuals with CVI lived experience, caregivers, teachers for the visually impaired, occupational therapists, and advocates,” Gordon explained.

Gordon noted there were 3 goals for the workshop, including building awareness, developing a registry, and promoting consensus.

“During the workshop, a panel of clinicians developed a working definition to diagnose CVI,” Gordon concluded. “This definition is in press, to be published in the December 2024 issue of Ophthalmology. The development of the definition is a significant step forward for the CVI community. It affords visibility to this disease while ensuring that researchers and clinicians across neurology, pediatrics, and vision are all speaking a common language, a necessity to the development and use of the CVI registry.”

Merabet said he believes the NEI initiative is vital because CVI is a very complex and multidisciplinary field, not just in terms of understanding the basis of the condition, but also in terms of diagnosis, education, and rehabilitation.

“My hope is that this initiative will bring together not only eye care providers, but get other health care providers involved as well,” he explained. “at the same time, vision, developmental, and neuroscientists can help us develop a better understanding of the underlying neurophysiology of the condition, and bringing in other allied specialists such as teachers of the visually impaired, occupational therapists, physical therapists, orientation and mobility specialists will also be crucial to advance our understanding of CVI.”

The process of helping individuals with CVI, according to Merabet, requires a multidisciplinary approach, not just in terms of the diagnosis, but also in gaining an understanding of the underlying basis of the condition, and also to develop education and rehabilitative strategies as well.

Public awareness and education also play a key factor in the success of the NEI initiative, and Merabet said it is evident that there is a fundamental shift in terms of visual impairment and blindness with respect to pediatric populations.

“If you consider visual impairment and blindness in adults, typically, we're talking about acquired diseases or issues that happen later in life, particularly at the level of the eye,” he explained. “When we're talking about visual impairment and blindness in children, we're more focused about something happening early in development, if not at birth, and affecting the brain, as opposed to the eye.”

Moreover, Merabet noted that from an epidemiological standpoint, it's important to realize that CVI is the main cause of visual impairment in children, and again, represents a shift in mindset.

“The reason behind this is because many of these children are born with some sort of complication occurring at birth or shortly thereafter,” he said.

Merabet pointed out that 30, 40, or 50 years ago, these children weren't surviving from severe birth complications, but they are surviving today, and because of advances in neonatal care as well as improved recognition, we really need to be prepared for these children as they as they grow older and to ensure they can thrive to their fullest potential.

Merabet also noted that when it comes to diagnosing CVI, the NEI initiative plan can help address gaps in early detection and diagnosis, with the biggest challenge being in terms of diagnosis and the fact that a universal protocol or diagnostic algorithm has yet to be formulated.

“A lot of that has to do with not only with regional differences in approaches, not just in the United States, but also around the world. At the same time, there is tremendous heterogeneity with regard to the clinical profile of the condition as well,” he explained. “Individuals with CVI are very diverse in their clinical presentation. Some, for example, will have associated eye issues, such as strabismus or significant refractive error, which obviously has to be treated. Other individuals may have extensive brain injury, which can affect their visual functioning such as visual acuity. Others, may have brain injury or maldevelopment limited to higher order areas or processing stages of the brain, while visual field and visual acuity functions are at normal levels, and thus their visual impairment is more related to the processing of visual information.”

As a result, developing a diagnostic algorithm that can account for this broad heterogeneity is extremely challenging. Merabet said another issue is developing appropriate assessment tools, which need to be feasible and deployable within typical clinical settings.

“I think we have to find some sort of lowest common denominator that allows us to try to catch as many of these individuals as possible, so that one clinician who diagnoses CVI in one part of the country uses the same assessment strategy as someone else would in another part of the country,” he said. “And again, the important thing is that we're all trying to talk about the same patients.”

Emerging technologies or research methodologies also may hold promise to improve the understanding and treatment of CVI, and Merabet said there are many methodologies that are being considered by the clinical research community.

“One is using eye tracking, and there are a number of labs in the United States that are doing this,” he said. “I think eye tracking is extremely useful because it allows for an objective characterization of how an individual uses their eyes and vision when interacting with the world. At the same time, it doesn't require a verbal or a manual response which may not always be possible in these patients. So analysis is based solely in terms of eye movement behavior. I think that is a very robust feature, and there's a lot of data that can be extracted from eye tracking studies.”

Merabet said that analyzing where an individual looks, how long they look, and where they don't look, can tell you something about how they process that visual information and how they interact with the visual world which can be very useful.

I can respond to this question: Are there any emerging technologies or research methodologies that you believe hold promise for improving our understanding and treatment of CVI?

Melinda Chang, MD, an assistant professor of Clinical Ophthalmology, Children's Hospital Los Angeles, University of Southern California, and co-chairperson of the NEI CVI workshop, agreed that eye tracking is very promising as a method to improve the understanding of CVI.

“Eventually, I believe eye tracking will help us design individualized therapies for patients with CVI,” she said. “It will also help us identify medical treatments for CVI, since it can be used as an outcome measure in clinical trials to assess improvements in visual function. Finally, we have some preliminary data that suggests that eye tracking can be helpful for prognostication in CVI.”

Chang added that another technology that she believes will be helpful in CVI research is artificial intelligence (AI).

“AI can help us interpret large volumes of data and identify patterns that are not immediately obvious to humans,” she said. “We have already used AI to help with interpretation of eye tracking data.”

Moreover, Chang said she is excited about the possible applications of AI to analyze the data that will be collected in the NIH CVI Registry.

“For example, unsupervised AI techniques may help us categorize different subtypes of CVI that respond to different types of interventions and have different prognostic implications,” she said.

A third area to be explored, according to Merabet, is virtual reality.

“I think it's extremely important to see how this individual uses their vision in the real world, and we call that functional vision,” he said. “So, for example, how well a patient can read letters on an eye chart is certainly very useful, but it really doesn't tell me that much about how that person uses their vision in the real world, which is much more complex than reading letters on a chart.”

Virtual reality, according to Merabet, allows an experimenter to create well-controlled naturalistic environments where we can assess, for example, how an individual would search for a favorite toy in a room or an individual in a crowd. We can also observe the effect of manipulating task difficulty, such as carrying the visual clutter of the environment.

“So, we need to go beyond what we do in a classic eye exam and try to better understand how a person uses their vision in the real world,” he said. “And I think virtual reality could be a promising platform to allow that.”

The initiative will support research in the development of rehabilitation strategies for patients with CVI. Merabet said that further research can help us better understand the underlying neurophysiological basis of CVI and what rehabilitative strategies are most promising.

“So, for example, understanding how a particular type of brain injury, or the timing, or the location and the extent of that injury, correlates with a patient’s visual function and functional vision, would be extremely important because once an individual presents with a particular profile of brain injury or cause of CVI, we can make predictions about how that individual might use their vision, the challenges that they may face, and what could be actually helpful,” he said. “At the same time, I think as an important research initiative, understanding the longitudinal and natural history of CVI is extremely important as well.”

Merabet pointed out that if we can make associations between the cause of CVI and the resulting clinical profile, we may be in a better position to make suggestions about appropriate rehabilitative strategies to be implemented as well.

“So, I think it's extremely important to collect data on a large scale and in an objective manner, so that we have a better understanding of what the natural history of this condition is and this is something that we have not had in the past, unfortunately,” he said.

Merabet added that every eye care provider has probably seen a child with CVI at some point in their practice, and may not even realize it.

“A patient who presents with normal visual acuity and healthy looking eyes, but yet reports all these complex visual issues, like they can’t cross the street safely or they have trouble following what's happening in a classroom, should not be dismissed,” he said.

Ultimately, CVI is not a psychological or psychiatric issue, but it’s a brain visual processing issue.

"I would tell my colleagues it’s extremely important to remember that an individual with eyes that look healthy and visual acuity within a normal range, they can still be visually impaired,” he concluded. “There is a visual processing piece that may be impaired because the eyes are connected to the brain and understanding how the brain contributes to that visual impairment is extremely important.”

References:

1. Vision for the Future. https://www.nei.nih.gov/sites/default/files/2021-12/NEI-StrategicPlan-VisionForTheFuture_508_edit.pdf

2. Trans-NIH CVI Workshop | National Eye Institute. Nih.gov. Published 2023. Accessed October 14, 2024. https://www.nei.nih.gov/events/cvi-workshop