Cerebral/cortical visual impairment (CVI) has emerged as a leading cause of pediatric visual impairment in industrialized countries. Despite its prevalence, it lacked a definitive diagnostic definition. Neurologic injuries leading to CVI often go unrecognized until later in development, but early detection is critical to implement accommodative strategies during key developmental periods.
Diagnosis requires combining clinical history, directed questionnaires, neuroimaging, and functional vision tests. Specialized assessments such as visual evoked potentials and eye tracking are also valuable. The National Institutes of Health (NIH) recently convened a workshop to develop a standardized working definition to address inconsistencies in diagnosing and managing this condition. The report, published in Ophthalmology, outlines key elements set to shape future research and clinical practice for CVI.
“In the first descriptions of CVI,” the investigators wrote, “children demonstrated (often profound) decreased visual acuity associated with damage to the occipital cortex, optic radiations, or both. Many clinicians now have adopted a broader definition inclusive of CVI in individuals with higher-order visual processing deficits in the setting of normal to near-normal visual acuity.”
Previous research “defined CVI as ‘a verifiable visual dysfunction which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment.’” However, as the researchers described, this definition limits CVI to a “diagnosis of exclusion”, rather than a diagnosis with specific characteristics, or one with a specific pathology or etiology.
With the NIH’s work, CVI can now be thought to encompass a range of visual impairments caused by brain abnormalities that affect visual processing pathways, and is characterized by deficits in visual acuity and visual field, as well as functional vision (the ability to perform visual tasks). They wrote: "Neurologic disorders associated with CVI include, but are not limited to, hypoxic–ischemic encephalopathy, prematurity with periventricular leukomalacia, trauma, hydrocephalus, seizures (especially with epileptic encephalopathy), as well as genetic and metabolic conditions." While some structural abnormalities are detectable on standard neuroimaging, others may require more specialized imaging.
According to the working definition, the visual dysfunction associated with CVI is more severe than what can be attributed to coexisting ocular conditions such as optic nerve atrophy or retinopathy of prematurity. It can manifest as lower-order deficits (ie, reduced visual acuity, contrast sensitivity, or visual fields), or higher-order deficits (eg, challenges with motion perception, object and face recognition, visuospatial orientation, or simultanagnosia). CVI may coexist with conditions including autism or dyslexia, but it is not primarily a disorder of language, learning, or social communication. "It is also critical to understand that in this context, functional vision is unrelated to the terms functional vision loss or functional vision disorder, both of which are used to indicate nonorganic visual disturbances that are, in some cases, suspected to be psychogenic in origin," the working group described.
CVI must be distinguished from conditions such as amblyopia, which stems from ocular or binocular abnormalities, or delayed visual maturation, where visual function typically normalizes by six months. Other ocular comorbidities such as strabismus, nystagmus, oculomotor apraxia, absent vestibular–ocular reflex, delayed or dysmetric saccades, impaired pursuits, fixation instability, difficulties with binocular function, and accommodative insufficiency should be addressed to improve patients’ functioning, development, and quality of life, but are considered secondary to CVI, rather than part of its diagnosis.
Pediatricians play a key role in identifying children at risk for CVI. “Evidence is emerging that visual processing pathways have a sensitive period or window of time with active structural and functional brain alterations extending past the first decade,” the investigators wrote. “Whether these are dynamic physiologic changes or continued developmental processes remains an ongoing debate. It is important to realize that the timing of brain injury significantly impacts the functional, structural, and behavioral consequences of visual impairment.” A recently released American Academy of Pediatrics report provides guidance on recognizing early signs of CVI, and a CVI registry is under development to collect demographic and clinical data and guide future clinical trials and rehabilitation strategies.
CVI’s complex presentation and overlapping comorbidities require a multidisciplinary approach to care. Early intervention, lifelong support, and tailored educational and vocational planning are critical to improving quality of life for individuals with CVI. "Future research is needed to identify evidence-based medical treatments specific to CVI,” the researchers concluded. “Areas of future research include establishing the neurophysiological basis and timing of neuroplasticity in the developing brain of individuals with CVI, standardizing methods of visual assessment, clarifying the impact of underlying cause on visual manifestations, identifying prognostic markers, understanding how the functional deficits of individuals with CVI change throughout their lifespan, and evaluating the efficacy of proposed interventions and rehabilitation strategies.”
A full list of author disclosures can be found in the published research.
