CVI definition: A work in progress
Lotfi Merabet, OD, PhD
Working definition forwarded by NIH CVI Working Group
(Image credit: AdobeStock/merydolla)
Over the past several decades, vision researchers have recognized that cerebral/cortical visual impairment (CVI) is a leading cause of pediatric visual impairment in the US and other industrialized nations. CVI is based in the brain and is a diagnostic entity distinct from cortical blindness.
The National Eye Institute (NEI) recognized CVI as a priority area for research as part of its 2021 NEI Vision for the Future Strategic Plan. It partnered with the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke within the National Institutes of Health (NIH) to sponsor a CVI workshop in November 2023, according to the cochairs of the CVI Working Group, Melinda Y. Chang, MD; and Lotfi B. Merabet, OD, PhD. The workshop was a collaborative effort with the entire NIH CVI Working Group.
Chang is from Children’s Hospital Los Angeles, Division of Ophthalmology, Department of Surgery, and the Department of Ophthalmology, University of Southern California, both in Los Angeles. Merabet is from Massachusetts Eye and Ear and the Harvard Medical School Department of Ophthalmology, both in Boston.
The NIH CVI Working Group proposed that “CVI is a neurodevelopmental disorder characterized by deficits of visual function and functional vision that are caused by neurologic damage to visual pathways and processing areas in the brain.” The definition devised by the CVI Working Group, comprising clinicians who were experts in diagnosing CVI, was published in Ophthalmology.1
Background
The panelists explained that although cortical blindness in adults is characterized by almost complete visual loss resulting from bilateral lesions of the occipital cortex that can result from insults such as posterior circulation strokes,2 the lesions in patients with CVI can reach beyond the early visual processing pathways and occipital cortex and cause visual deficits that are more than decreased visual acuity.3-6 The affected patients usually are not completely blind and have some level of visual function and functional visual abilities that may improve with time.2,7,8
According to the panelists, when clinicians started to study CVI, they initially focused on children with profound decreases in visual acuity related to damage to the occipital cortex and/or optic radiations.2,9 “Many clinicians now have adopted a broader and more inclusive definition of CVI as many individuals have higher order visual processing deficits in the setting of normal to near-normal visual acuity,” they said.10-12
They cited a study by Sakki et al,13 who in 2018 proposed a definition that 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.” This was an important but limited definition that primarily focused on differentiating CVI from ocular-based causes of visual impairment, which may coexist in some patients, but it did not further characterize the types of visual deficits in patients with CVI, the panelists explained.
CVI Working Definition
The CVI Working Group, which met in Bethesda, Maryland, on November 16 and 17, 2023, identified 5 key elements.
CVI encompasses a spectrum of visual impairments caused by an underlying brain abnormality that affects the development of visual processing pathways and is characterized by deficits in visual function and functional vision.
The visual dysfunction in CVI is greater than expected by any comorbid ocular conditions alone.
The visual dysfunction in CVI may manifest as lower-order or higher-order afferent visual deficits or both, leading to characteristic behaviors in affected individuals.
Although CVI may be comorbid with other neurodevelopmental disorders, CVI is not primarily a disorder of language, learning, or social communication.
The underlying neurologic insult of the developing brain may go unrecognized or undiagnosed until later in life.
The 5 elements include most affected patients, the panelists believed more discussion is needed to refine the definition further. They stated, “Future work is needed to achieve consensus on nomenclature, diagnostic criteria, and strategies for early identification and intervention. The NIH is developing a CVI registry to collect relevant demographic and clinical data prospectively and longitudinally to help inform future research questions and to provide insight into considerations for future clinical trials in the field of CVI.”
The panelists pointed to the need to establish standardized diagnostic criteria for CVI and considerations for identifying individuals with high suspicion of having CVI, as well as standardized nomenclature of CVI (ie, cortical vs cerebral) for appropriate clinical care (especially early diagnosis) and research.14 An editorial in Ophthalmology15 accompanying the NIH CVI Working Group report noted the importance of the refined definition.
Practically speaking, the editorialists from the NIH stated that the absence of a uniform clinical presentation of CVI is confounding. “In some cases, visual acuity can be profoundly affected.16 In other cases, acuity may be near normal, but patients have higher-order deficits such as difficulties in visual search, complex motion perception, or facial recognition. Behaviorally, a child may struggle to recognize a parent in a crowded room or find a specific toy in a toy box.16 As a condition with such heterogeneous manifestations, where patients are followed by different clinicians (eg, ophthalmology, optometry, neurology, pediatrics, rehabilitation), clinical diagnosis can slip through the cracks.”
They said, “Our hope is this new definition will help health care providers, including ophthalmologists and optometrists, pediatricians, and neurologists, better understand the diverse CVI presentations and promote earlier diagnoses. Individuals with CVI have different touchpoints within the care continuum, and diagnosis may require multidisciplinary coordination between different specialists. Children with suspected neuronal injury or common comorbidities such as cerebral palsy and autism should be screened for CVI. In addition, greater awareness of CVI in the broader community, including parents, educators, and therapists, may help address underdiagnosis and lead to improved access to care.” •
References
1. Chang MY, Merabet LB; CVI Working Group. Special commentary: cerebral/cortical visual impairment working definition: a report from the National Institutes of Health CVI Workshop. Ophthalmology. 2024;131(12):1359-1365. doi:10.1016/j.ophtha.2024.09.017
2. Whiting S, Jan JE, Wong PK, Flodmark O, Farrell K, McCormick AQ. Permanent cortical visual impairment in children. Dev Med Child Neurol. 1985;27(6):730-739. doi:10.1111/j.1469-8749.1985.tb03796.x
3. Dutton G, Ballantyne J, Boyd G, et al. Cortical visual dysfunction in children: a clinical study. Eye (Lond). 1996;10(pt 3):302-309. doi:10.1038/eye.1996.64
4. Good WV, Jan JE, DeSa L, Barkovich AJ, Groenveld M, Hoyt CS. Cortical visual impairment in children. Surv Ophthalmol. 1994;38(4):351-364. doi:10.1016/0039-6257(94)90073-6
5. Chang MY, Borchert MS. Advances in the evaluation and management of cortical/cerebral visual impairment in children. Surv Ophthalmol. 2020;65(6):708-724. doi:10.1016/j.survophthal.2020.03.001
6. Martín MB, Santos-Lozano A, Martín-Hernández J, et al. Cerebral versus ocular visual impairment: the impact on developmental neuroplasticity. Front Psychol. 2016;7:1958. doi:10.3389/fpsyg.2016.01958
7. Handa S, Saffari SE, Borchert M. Factors associated with lack of vision improvement in children with cortical visual impairment. J Neuroophthalmol. 2018;38(4):429-433. doi:10.1097/WNO.0000000000000610
8. Matsuba CA, Jan JE. Long-term outcome of children with cortical visual impairment. Dev Med Child Neurol. 2006;48(6):508-512. doi:10.1017/S0012162206001071
9. Jan JE, Groenveld M, Sykanda AM, Hoyt CS. Behavioural characteristics of children with permanent cortical visual impairment. Dev Med Child Neurol. 1987;29(5):571-576. doi:10.1111/j.1469-8749.1987.tb08498.x
10. Kran BS, Lawrence L, Mayer DL, Heidary G. Cerebral/cortical visual impairment: a need to reassess current definitions of visual impairment and blindness. Semin Pediatr Neurol. 2019;31:25-29. doi:10.1016/j.spen.2019.05.005
11. Good WV, Jan JE, Burden SK, Skoczenski A, Candy R. Recent advances in cortical visual impairment. Dev Med Child Neurol. 2001;43(1):56-60. doi:10.1017/s0012162201000093
12. Chandna A, Ghahghaei S, Foster S, Kumar R. Higher visual function deficits in children with cerebral visual impairment and good visual acuity. Front Hum Neurosci. 2021;15:711873. doi:10.3389/fnhum.2021.711873
13. Sakki HEA, Dale NJ, Sargent J, Perez-Roche T, Bowman R.
Is there consensus in defining childhood cerebral visual impairment? a systematic review of terminology and definitions. Br J Ophthalmol. 2018;102(4):424-432. doi:10.1136/bjophthalmol-2017-310694
14. Lueck A, Harpster K, Hartmann E, et al. Toward removing barriers in the evaluation, diagnosis, and care of individuals with cerebral visual impairments. Policy Insights Behav Brain Sci. 2023;10(2):296-307. doi:10.1177/23727322231195213
15. Gordon S, Kerr A, Wiggs C, Chiang MF. What is cerebral/cortical visual impairment and why do we need a new definition? Ophthalmology. 2024;131(12):1357-1358. doi:10.1016/j.ophtha.2024.09.011
16. Oliver H, Seccurro D, Dorich J, Rice M, Schwartz T, Harpster K. “Even though a lot of kids have it, not a lot of people have knowledge of it”: a qualitative study exploring the perspectives of parents of children with cerebral/cortical visual impairment. Res Dev Disabil. 2023;135:104443. doi:10.1016/j.ridd.2023.104443
Melinda Y. Chang, MD
e: Melinda.y.wu@gmail.com
Chang is from Children’s Hospital Los Angeles, Division of Ophthalmology, Department of Surgery, and the Department of Ophthalmology, University of Southern California, both in Los Angeles. She reported receiving financial support from the Knights Templar Eye Foundation, the National Eye Institute (grant number: K23EY033790), and Research to Prevent Blindness.
Lotfi Merabet, OD, PhD
e: Lotfi_Merabet@meei.harvard.edu
Merabet is from Massachusetts Eye and Ear, and the Department of Ophthalmology, Harvard Medical School, both in Boston. He has no financial interest in this work.
Both authors contributed equally to this work and are cochairs of the CVI Working Group.
