Historically referred to as “cortical blindness,” cortical visual impairment (CVI) has been misperceived for decades as brain damage that causes an irreparable loss of vision or blindness. Advances in visual neuroplasticity research, however, show the opposite is true. Functional vision in children with CVI is expected to improve with appropriate assessment and intervention. 1
CVI is a brain-based visual impairment that occurs when the post-geniculate visual pathway is damaged.2 It is most commonly caused by hypoxic ischemic encephalopathy (HIE), periventricular leukomalacia (PVL), hydrocephalus, seizure, metabolic disease, infection, or head trauma, such as shaken baby syndrome. CVI is the leading cause of pediatric visual impairment in developed countries, and is now also the leading cause in developing countries. It has been appropriately labeled a public health crisis. Still, despite its prevalence and recent urgency, we do not yet have a standardized method of visual assessment for children with CVI in the clinical setting.3
Over the last few years, however, researchers have investigated newer methods of clinical assessment and potential evidence-based treatments for children with CVI. “Tools to assess other aspects of vision in children with CVI include questionnaires for structured history taking, functional vision assessment with the CVI Range, visual perception testing with neuropsychological batteries, and eye tracking”.3 Ongoing research aims to compare the reliability of these assessments with others, such as forced-choice preferential looking, visual behavior assessments using Huo’s 6-level visual acuity scale, sweep visual evoked potentials (sVEP), and visual perception testing, such as the Children’s Visual Impairment Test (CVIT) for young children.4-5
While review of the validity of these existing tools evolves, modifications to the traditional optometric exam aim to support these children and their long-term intervention plan.
Depending on the severity of the neurological event and damage to the visual pathways, CVI presents with a unique set of characteristics and visual behaviors that require unique assessment, intervention, and educational planning, according to a 2020 Survey of Ophthalmology publication.6
The American Association for Pediatric Ophthalmology and Strabismus (AAPOS), along with the evidence-based research of Christine Roman-Lantzy, PhD, point to 10 distinct visual behaviors and characteristics that can help identify children with CVI. These include:7
- Dependence on lights
- A need for movement
- Distinct color preferences
- Demonstrated visual latency
- Visual field preferences
- Abnormal visual reflexes
- Difficulty with visually guided reach
- Difficulty with novelty (environment, people, materials)
- Difficulty attending to or interpreting visually complex environments, array, individual targets, and faces
- Difficulty with distance viewing
Knowing the impact of each of these characteristics on the individual child’s functional vision will help optometrists accurately plan their exam to ensure the child’s most accurate results.
While the optometric exam should still include all customary components including patient history, eye health examination, visual acuity, and preliminary tests measuring depth perception, color vision, eye muscle movements, visual field, and pupillary response, clinicians will need to address that child’s unique, individual visual behaviors and characteristics to receive optimal results.8
“Preparation is key,” says Nicole Ross, OD, optometrist and assistant professor at New England College of Optometry (NECO) Center for Eye Care, Perkins School for the Blind, “And it demands a thorough review of the child’s medical history and records.” Medical histories in this population can often be very complex.
Additional records may include exam reports from the child’s neurologist, neuro-ophthalmologist, pediatrician, or neuropsychologist. Documents should include an Individual Education Program (IEP) and functional vision assessments from teachers of students with visual impairments (TVIs) and assessments by other service providers on the child’s educational team. Questionnaires and inventories compiled by parents can be equally useful. These documents and interviews can provide the essential baseline to the child’s visual behaviors before the optometrist even begins preparing material and adaptations to the exam protocol.
“I’ve found that treating a child with CVI is almost always collaborative,” adds Dr Ross. “And, I think some doctors are hesitant to do it, but engaging parents will almost always make for a better exam because once we know more about that child and their behaviors and skills and limitations we can determine what materials do we need, what tests do we still need to do to pull more information; in essence, want to match the evaluation to the abilities and needs of the child.”
Optometrists who have had success engaging their young patients with CVI, by receiving more accurate readings for acuity, field, and visual behavior, stand behind the need to adapt. Using 3D instead of 2D objects, with reduced visual clutter, highly saturated colors, and incorporating light and movement when possible, can help to directly address the visual characteristics and needs of a child with CVI.
“You have to be willing to be creative, get down on the floor with the child, learn what excites them, visually, before knowing what you’re going to use and how,” comments Katherine Green, OD, who serves as an assistant professor and director of Nova Southeastern University’s Acquired Brain Injury clinic.
Beyond their unique visual behaviors, knowing a child’s level of functional vision is important before starting the exam. Children diagnosed with CVI can present on a wide spectrum, each with a distinct set of visual and behavioral responses, so it’s important to know where, or in which “phase” the child is presenting. The CVI range, for example, is based on a continuum of 0 to 10. A child with a score of 0 is responding little or not at all to stimuli and visual targets, while a child nearing a score of 9 or 10 is demonstrating near typical visual function.1
“Throughout the exam, I’ll explore, ‘do they respond at all to light, do they prefer different colored flashlights, or movement when I move them around in near distance, can I use a mirror to redirect the overhead light, and can they track this?’” adds Dr Green. “A lot of tools that I would use in a typical pediatric, infant, or toddler exam — such as LEA shape matching, Cardiff Cards with pictures instead of the Teller card straight lines, Berkeley Rudimentary Vision Test cards, the Feinbloom Low Vision Chart — I’ll still use in an exam with a child with CVI, I’ll just present them differently.”
Dr Green shares that her exam toolkit also includes a tablet device for preferred backlighting and low complexity, and high contrast apps encouraging eye tracking. She uses some low complexity toys, such as a doll with an illuminated orange head, familiar stuffed animals and puppets, LEA symbol matching cards, and pieces of cardboard with cutouts to reduce complexity on her charts.
“These are adaptations that would probably help most kids — limited material on a page, backlit materials, presenting one question at a time, but especially with our kids with visual processing and spatial crowding issues, those supports are even more important,” says Dr Green.
Also, if the child is nonverbal, asking the parent to bring along the child’s augmentative and alternative communication (AAC) device can create a more comfortable environment and more patient engagement. If the child is not able to respond verbally or point to a selection during the exam, the optometrist may utilize eye-gazing technology, preferential-looking activities, or more technical tests such as EEG, EOG, or sweep VEP. Accuracy and usefulness of results from these tests are highly dependent on the child’s ability to sustain the required preparation and engage with the clinician.3
Accessibility Through Flexibility
Just as materials should be adapted to match the visual functioning and behaviors of the child, so should the exam procedure itself.
Acuity can be measured by requiring the child to engage with a less complex target (a single object at a time) that incorporates light to elicit visual attention. Electronic eye charts can also come in handy, as the optometrist can isolate symbols or letters and adapt the presentation, reducing crowding ratio. The confrontational method test for visual field evaluation can incorporate a light wand or illuminated target of a certain color (yellow and red are notably preferred for children with CVI).1 Instead of using the very complex targets on the Waggoner cards, a child with CVI may demonstrate their contrast sensitivity with an adapted shape puzzle or by searching for a motivating toy on surfaces of varying complexity or contrast. Asking questions with simpler directives and allowing for longer response time is important when working with children with CVI. Verbal coaching can interrupt their process to listen, interpret and respond.
As Dr Ross notes, “I’ll use a board where the symbols are further spaced. I’ll ask simple directives instead of multi-step directives. I may ask them which shape is the circle, from a selection of 2 shapes instead of 4.” These adjustments to the typical exam can cause acuity to vary, and should be added to the notes in the exam report.
“We should be prepared,” says Dr Ross, “that sometimes, none of these formal tests will be engaging to the child and you’ll have to adapt things on the fly. One time, for a patient that was nonverbal, I tested acuities with the only motivating object we had in the room — a cheerio.”
Appreciating the unique visual needs of these children and opening the floodgates of creativity can allow the clinician to address the child’s unique visual preferences. Only then are we accounting for the difficulty to visually attend, fixate, and interpret targets and provide a fair exam.
“Overall, you have to be flexible,” says Dr Ross, “and this means flexible with switching up the order of your traditional exam, incorporating the parent to build rapport and a comfortable relationship, and getting the child to engage in the activities.”
Post Exam Referrals
Post exam protocols for the child with CVI may include requesting more frequent visits to monitor progress as well as making referrals to other professionals in the community familiar with their needs.9
Dr Ross emphasizes the importance of connecting children and families with a TVI, certified orientation and mobility specialist (COMS), occupational therapist (OT), or other service providers to ensure they receive the right educational assessments and have what they need to reach their potential.
Similarly, AAPOS suggests that each child with CVI receive a functional assessment by a TVI or other qualified team member familiar with their unique needs, to provide appropriate recommendations and accommodations. This assessment essentially guides the treatment process for each child.7
“I’ll say that since working with children with CVI, it’s been rewarding to see my patients grow into their ability to explore the visual world around them,” says Dr Ross. “They are often capable of doing so much more than we thought, we just have to get them set up to succeed.”
Last month, the National Eye Institute (NEI) Strategic Planning Agenda, “Vision for the Future 2021-2025” stated that “CVI management requires different approaches than ocular causes of vision loss, and schools for the blind have successfully adopted new techniques to teach children with CVI. However, we are still in the early stages of understanding CVI, and more research is needed to accurately diagnose and optimally treat those affected.”10
While optometrists will not see a total resolution of CVI in pediatric patients, standardized assessment, targeted intervention, and ongoing monitoring of eye health is critical. The clinical research indicates a window of “best opportunity” exists. Strategic interventions provided in the first 12 months of life have shown significant functional vision improvement. These improvements can continue into adolescence with “meaningful and consistent intervention,”.11 On the contrary, failure to diagnose CVI and appropriately intervene could drastically hinder the child’s development and access to education.
Dr Green advises physicians to approach these protocols a single patient at a time. “When you see a child show improvements, after following a CVI-specific protocol and working with an informed team, you think, ‘hey, what can I do differently to get those improvements every time?’”
Francesca Crozier-Fitzgerald is a Certified Teacher of Students with Visual Impairments (CTVI) Director, CVI Collaborative Center, Miami Lighthouse for the Blind and Visually Impaired.
1. Roman-Lantzy C. Cortical visual impairment: an approach to assessment and intervention. 2nd ed. Louisville, KY: AFB Press; 2007.
3. Chang MY, Borchert MS. Methods of visual assessment in children with cortical visual impairment. Curr Opin Neurol. 2021;34(1):89-96. doi:10.1097/WCO.0000000000000877
4. Huo R, Burden SK, Hoyt CS, Good WV. Chronic cortical visual impairment in children: Aetiology, prognosis, and associated neurological defects. Br J Ophthalmol. 1999; 83(6):670-675. doi:10.1136/bjo.83.6.670
5. Vancleef K, Janssens E, Petré Y, Wageman J, Ortibus L. Assessment tool for visual perception deficits in cerebral visual impairment: development and normative data of typically developing children. Dev Med Child Neurol 2020; 62(1):111-117. doi:10.1111/dmcn.14303
6. Chang MY, Borchert MS. Advances in the evaluation and management of cortical cerebral visual impairment in children. Surv Ophthalmol. 2020;65(6):708-24. doi:10.1016/j.survophthal.2020.03.001
7. Cortical Visual Impairment. American Association for Pediatric Ophthalmology and Strabismus. https://aapos.org/glossary/cortical-visual-impairment. Updated February 2019. Accessed December 13, 2021.
8. Comprehensive eye exams. American Optometric Association. https://www.aoa.org/healthy-eyes/caring-for-your-eyes/eye-exams?sso=y. Accessed December 13, 2021.
9. Rice ML, Sandoval MA, Castleberry KM, Schwartz TL. Physician prescribing and referral patterns in children with cerebral visual impairment. Optom Vis Sci. 2021.;98(9):1078-1084. doi:10.1097/OPX.0000000000001775
10. National Eye Institute Strategic Plan — Vision for the Future, 2021-2025. https://www.nei.nih.gov/sites/default/files/2021-12/NEI-StrategicPlan-VisionForTheFuture_508_edit.pdf Updated November 2021. Accessed December 12, 2021.
11. Wilkinson K, Wolf S. An in-depth case description of gaze patterns of an individual with cortical visual impairment to stimuli of varying complexity: implications for augmentative and alternative communication design. PERSP. Published online October 20, 2021. doi:10.1044/2021_PERSP-21-00111