CVI refers to a temporary or permanently reduced visual response that results from damage in the brain's occipital lobes or the posterior visual pathways. The degree of visual impairment varies between severe visual impairment and complete blindness.
In developed countries, the condition has become the main cause of visual impairment among children making it a significant public health concern. When the condition is first detected in a child, s/he may appear blind, but over time, vision improves.
Since the condition often coexists with ocular visual loss and can be caused by several neurologic diseases, a child must see both a pediatric ophthalmologist and a neurologist.
Also Known As
- Neurological visual impairment
- Cerebral visual impairment
- Brain damage related visual impairment
Causes & Risk Factors
On ordinary occasions, the eyes transmit information to the brain via the optic nerves. The brain then recognizes and integrates the information, causing motor responses to the befitting organs. In the presence of CVI, the brain fails to properly integrate information due to abnormal functioning that could be as a result of:
- Hypoxic ischemic encephalopathy
- Metabolic disorders
- Traumatic brain injury
- Severe epilepsy
- Pedi ventricular leukomalacia
- Neonatal hypoglycemia
CVI may also occur due to developmental defects in the central nervous system, cardiac arrest, twin pregnancy, or antenatal drug use by a mother.
Signs & Symptoms
Common CVI symptoms include:
- Blunted social gaze
- Poor visual acuity
- Abnormal response to light (photophobia/light gazing)
- Loss of visual field
Teachers, parents, and specialists may also notice some behaviors in the child, such as:
- Lowered response to visual stimulants in the presence of other sounds or when touching the child
- Unexpectedly good vision for navigation
- Inadequate response to unfamiliar stimuli
- Variable visual responses to equivalent stimuli
- Greater attention to moving stimuli compared static ones
- Better use of peripheral vision than the side vision
- Tiring from visual tasks
- Trouble seeing images in busy backgrounds
Diagnosing CVI may be difficult, and in the past, professionals would conclude that a patient was faking their situation. Presently, techniques that do not entirely depend upon a patient's words and actions are available. The procedures involve a full eye examination to evaluate visual functioning, brain imaging since most patients have a history of neurological issues and the use of electrodes.
An ophthalmologist or neurologist typically diagnoses CVI, although, in some countries, an optometrist may also perform the task. A child can be said to have CVI when:
- An eye exam fails to explain the visual loss fully
- The child has a history of a neurological condition even when brain imaging results come out normal
- The child presents extraordinary behavioral and visual traits that have been identified in research centers
The child needs to receive treatment for underlying neurologic diseases and other eye conditions that could affect vision further. For the other ocular conditions, the doctor may prescribe eyeglasses or eye muscle surgery.
After the doctor diagnoses a child with CVI, s/he should undergo a functional assessment in an appropriate local agency. Based on the child's behavioral traits, the evaluation provides recommendations and interventions that enable a child to utilize their vision efficiently.
It is vital to introduce a child to the devised interventions at an early age because the interventions help in stimulating visual development. Some helpful stimulation for infants include:
- Sound or touch to gain a child's attention
- Extra response time for visual stimuli
- Presenting visual materials from various angles
- Large, lighted, reflective, high contrast, and moving objects
- Presentation of visual materials in a simple, uncluttered way
- Avoidance of overstimulation
- Variable light levels in the setting
- Avoidance of tasks when the child is frustrated, tired, or hungry
Prognosis & Long-Term Outlook
The brain matures as the child grows and so it can develop new connections that would fix the initial injury as well as improve function. Vision specialists and teachers with good knowledge about CVI can assist with evaluation and appropriate intervention strategies that enhance a child's visual performance. For these reasons, many children show visual improvements over time. According to a research by Dr. Roman Lantzy, 97% of patients from his study group developed an improved vision in averagely 3.7 years.
Patients differ in the level of vision acquired due to differences in the type of injury, age of onset, cause, and severity. In patients with subcortical damage, epilepsy, and bacterial meningitis, the prognosis is usually poor.
Despite improved vision in many CVI patients, more than 90% remain visually handicapped with poor neurodevelopmental outcomes.
Prevention & Follow Up
A variety of researches targeting to prevent the development of CVI are emerging, and the early detection of children at risk of developing CVI is prospective. Some interventions are known to possibly decrease the advancement of cortical injury where the cause of impairment is hypoxia and perinatal ischemia.