NIH-Led Science Team Defines Elements of Cerebral Vision Impairment

Cerebral (or cortical) vision impairment (CVI) is a leading cause of childhood vision impairment in the United States and other industrialized nations, affecting at least 3% of primary school children. As vision is closely tied to learning, delayed or missed diagnoses of CVI can have negative effects on overall childhood development. 

Experts convened by the National Institutes of Health (NIH) have published a new definition of CVI with five key elements to help multidisciplinary eye care providers better recognize the disease. They just published these findings as a report in Ophthalmology. 

“Lack of awareness about CVI is a large factor leading to it to be misdiagnosed or undiagnosed, which can mean years of frustration for children and parents who are unaware of an underlying vision issue and don’t receive help for it,” Lotfi B. Merabet, OD, PhD, associate professor of ophthalmology at Massachusetts Eye and Ear and Harvard Medical School and co-author of the report, said in a recent press release.

CVI can be difficult to diagnosis because there is no uniform clinical presentation. In many children, visual acuity can be near perfect. Behaviorally, a child may struggle to recognize a parent in a crowded room or find a specific toy in a toybox. Other factors that may contribute to missed diagnoses are decreased provider awareness and lack of a universal definition. That's why the NIH-group aimed to identify five elements of the condition to help facilitate a differential diagnosis from similar conditions. 

“Clarifying the factors for suspecting CVI should help build awareness and help eye care providers identify children for further assessment so they can benefit from rehabilitation and accommodation strategies as early as possible,” Melinda Y. Chang, MD, assistant professor of clinical ophthalmology at the University of Southern California and co-author, said.  

The five elements of CVI are outlined below:

• Brain Involvement: CVI is now described as a spectrum of visual impairment caused by an underlying structural or functional brain abnormality that impacts the development of visual function and processing.
• Visual dysfunction greater than expected based on eye exam: CVI should be considered when visual dysfunction seems to be based on a visual processing disorder and cannot be fully explained by an ocular co-morbidity. 
• Types of visual deficits: Patients with CVI may experience both lower-order and higher-order visual deficits. Examples of lower-order deficits include impaired visual acuity, reduced contrast sensitivity and reduced visual field. Higher-order deficits can include difficulty with face and object recognition, lessened ability to visually search for something or someone, difficulty with spatial orientation or complex motion perception, and seeing more than one object at a time. Recognizing the type of visual deficit can explain some of the characteristic behaviors in affected individuals.
• Distinguishing overlapping neurological disorders: While CVI can co-occur with other neurodevelopmental disorders, it is not primarily a disorder of language, learning, or social communication. Common misdiagnoses include cerebral palsy, autism, and dyslexia. 
• CVI is easily missed: The underlying neurological abnormality of a child’s developing brain may go unrecognized or undiagnosed until later in life. Therefore, screening for CVI should be considered in individuals who are at high risk of having had a neurological injury, such as infants born prematurely.

“Significant work remains to be done to optimize diagnostic approaches and multidisciplinary rehabilitation strategies to improve quality of life for people with CVI, which is why it is a priority in our strategic plan,” Michael F. Chiang, MD, director of NIH’s National Eye Institute (NEI), said. 

To advance research, the NIH is developing a CVI registry to collect relevant demographic and clinical data from affected individuals. This resource will be made available for researchers to further study the best diagnostic and management strategies.