A Primer on Cortical Visual Impairment

We owe the parents of children with CVI a better explanation of their child’s condition. Here’s a look at how to start providing one.

Sharon S. Lehman, MD, Wilmington, Del.
9/5/2013

Parents of children with cortical visual impairment deserve more of an explanation of their child’s condition than, “The eye examination is normal. No glasses are necessary.” In the past, eye-care providers, including ophthalmologists, were often uncomfortable when dealing with the patient and family with a complex set of challenges. There was a perceived dismal prognosis with no hope of recovery. Cortical visual impairment, which is already the most common cause of vision loss in children in developed countries, will increase in incidence as medical technology and research continue to improve survival.1 Better information and more tools can assist the ophthalmologist in providing patients with care.

Definition & Characteristics


Cortical visual impairment is defined as bilateral visual impairment, involving acuity and/or higher visual functions, such as visual motor planning, due to posterior visual pathway disease. It is one component of a global neurologic process.

Patients with cortical visual impairment often display characteristic behaviors that may improve or resolve as the child improves. These characteristics include: light gazing; photophobia; poor visual attention; preferences for certain colors; visual field abnormalities; difficulty with visual complexity; problems with viewing distance; eccentric viewing; atypical visual reflex behaviors; and variability with contrast.2 These characteristics may resolve as a patient improves. A detailed history may reveal previously present characteristics.

Causes

Figure 1. Axial CT scan illustrating hydrocephalus with volume loss and damage to optic pathways resulting in cortical visual impairment.
Sean P. Donahue, MD, PhD, and colleagues have demonstrated that the most common causes of cortical visual impairment in children are perinatal hypoxia, prematurity and hydrocephalus.3 Other etiologies in children and adults include: traumatic brain injury; stroke; congenital anomalies; central nervous system infections; neonatal hypoglycemia; and seizures.4

These patients may have co-morbidities and associated deficits that make the identification, evaluation, treatment and rehabilitation of the patient more difficult. R. Michael Siatkowski, MD, and colleagues have shown that premature infants are particularly vulnerable to anterior and posterior visual pathway disease, which may complicate the identification of the cause of vision loss.5

Pathophysiology

Melvyn A. Goodale, PhD, and A. David Milner, PhD, described the two-stream hypothesis of neural processing in 1999. Information concerning recognition of objects travels from the occipital cortex to the inferior temporal cortex (ventral stream). Information concerning the location of objects and control of movements to locate objects in space travels from the occipital lobe to the parietal lobe (dorsal stream).6 Pathophysiology affecting the ventral stream may cause difficulty with object and facial recognition. Pathophysiology of the dorsal stream may cause difficulty locating objects and visual motor planning (visual guidance of movements).

Originally, it was thought that these two systems were separate entities; however, more recent research indicates that processing of complex visual information requires connections between the ventral and dorsal streams.7

Classroom learning is largely vision-based. Both ventral and dorsal stream pathology may hinder educational progress, unless accommodations and interventions are made. Activities of daily living are also highly dependent on vision. A child’s independence in routine activities may also be affected and require deficit- based compensation.

Table 1. CVI Internet Resources
1. American Printing House for the Blind
aph.org/cvi


2. American Foundation for the Blind
afb.org

3. American Association for Pediatric Ophthalmology
and Strabismus
aapos.org

4. Little Bear Sees
littlebearsees.org
 
Periventricular leukomalacia and perinatal stroke make premature infants particularly vulnerable to visual pathway damage, resulting in the previously described typical visual characteristics associated with cortical visual impairment. Visual performance often mirrors the global neurologic deficit. More severely affected patients with quadriplegic cerebral palsy often have more limited visual performance. Patients with diplegic cerebral palsy may have better visual acuity and performance but may demonstrate visual field deficits and higher-level function deficits.

Classification and Prognosis


Christine Roman-Lantzy, PhD, has described a spectrum of phases that correlate with the severity of visual characteristics displayed by a patient with cortical visual impairment. Phase I is the lowest level of function, where a patient displays minimal visual responses. Phase II is a higher level where visual performance is linked to improved function. Phase III is the highest level of performance, where some typical characteristics may become extinct.8 Patients may progress from one phase to another with improvement in function. This type of classification provides a common language for families and the multidisciplinary team caring for a child. It is also the basis for providing interventions and accommodations that may be used to assist a patient with cortical visual impairment in the educational setting and with activities of daily living.

In the past, cortical visual impairment was called cortical “blindness,” with a perceived poor prognosis. Although some patients may not have any improvement, studies have shown that the majority of patients have at least some improvement in vision.9 It is important to communicate this fact to families when the diagnosis of cortical visual impairment is made.

It is important to educate families as well as other health-care providers who may treat children with cortical visual impairment in order to prevent inaccurately poor prognostic predictions. Baseline visual acuity at diagnosis cannot be used to predict final visual performance. The degree of damage demonstrated on brain imaging studies cannot be used to predict final visual performance either.

The Ophthalmologist’s Role

The ophthalmologist is an important member of the multidisciplinary team that cares for a child with cortical visual impairment.

During the history taking, it is important to solicit observations of visual performance from the family and other members of the child’s care team. A child’s performance in a limited examination time, in an unfamiliar place when he may be tired and hungry, may not be representative of true function. It is often the occupational or physical therapist who first notes a visual field defect in a patient.

Baseline visual acuity at diagnosis cannot be used to predict final visual performance. The degree of damage demonstrated on brain imaging studies cannot be used to predict final visual performance either.
A full ophthalmologic examination, including cycloplegic refraction, should be performed in order to assess visual acuity, look for characteristics of cortical visual impairment, and identify the presence of clinically significant ocular conditions. Visual performance can be maximized by treating any ocular co-morbidities, including any significant refractive errors. Dynamic retinoscopy is a useful tool to evaluate for accommodative insufficiency.

It is vital for the ophthalmologist to make and document the diagnosis of cortical visual impairment, as well as reduced visual acuity, if present. Patients may qualify for services based on the level of visual impairment, especially if a patient has a chronic visual condition that will impair educational progress. Further assistance for interventions or accommodations that may help a patient reach his or her full potential depends on the diagnosis made by the ophthalmologist.

When appropriate, a referral for an evaluation for vision services from the appropriate agency should be made. The referral for infants and children prior to the third birthday can be made through their early intervention program or appropriate state agency, depending upon the patient’s state of residence. The referral for children age 3 and older is made through the school district or appropriate state agency.

The findings of the eye examination and diagnosis should be discussed with the family. Educational and resource materials should be provided. It is important to provide a list of websites with accurate information appropriate for the patient’s diagnosis, since many families primarily use the Internet for medical information. It is also helpful to have pre-printed information ready to give families whose child has a common diagnosis.

Specific recommendations for treatment, interventions and accommodations should be discussed with families, documented and given to families in writing as part of the discharge instructions.

Recommendations for interventions and accommodations should be based on the patient’s level of function and characteristics of impairment present. Suggestions for a low-functioning, 6-month-old, former preemie with periventricular leukomalacia and hypotonia in Phase I may include:

1. High-contrast, lighted and moving visual stimuli;
2. Avoid overstimulation;
3. Provide support for body when performing visual tasks;
4. Allow extra time for response to visual stimuli; and
5. Use auditory and tactile cues to attract and sustain visual attention.

Suggestions for a higher-functioning, school-age child with cerebral palsy in Phase III may include:

1. Allow extra time for response to visual stimuli because of processing and expressive delay;
2. Limit complexity and increase as tolerated;
3. Avoid graphite pencil on recycled paper;
4. Use black marker on white paper for written activities; and
5. Exploit auditory learning skills.

Children with a disability that interferes with educational progress who attend school accepting federal funds may qualify for an individualized educational plan, or IEP, under the Individuals with Disabilities Education Act (See idea.ed.gov.) It is important to document these needs and communicate appropriately with the family and other members of the child’s multidisciplinary team.

It is imperative for the ophthalmologist to be an active and involved member of the team caring for a child with cortical visual impairment. The ophthalmologist should provide diagnoses, referrals for services, treatment of ocular co-morbidities, education and advocacy for the patient. Interventions and accommodations allow the child with cortical visual impairment to attain his or her fullest educational potential and maximize independence in activities of daily living.   REVIEW


Dr. Lehman is the chief of ophthalmology at Nemours/AI duPont Hospital for Children, Wilmington, and a clinical professor of ophthalmology and pediatrics at Jefferson Medical College/Wills Eye Institute, Philadelphia.



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