TNOA Journal of Ophthalmic Science and Research

REVIEW ARTICLE
Year
: 2018  |  Volume : 56  |  Issue : 4  |  Page : 244--246

Cerebral visual impairment


Meenakshi Swaminathan, Yamini Patial 
 Department of Pediatric Ophthalmology, Sankara Nethralaya, Chennai, Tamil Nadu, India

Correspondence Address:
Dr. Yamini Patial
Number 41/Old Number 18, Sankara Nethralaya, College Road, Chennai - 600 006, Tamil Nadu
India

Abstract

In developing countries like India, cerebral visual impairment (CVI) is becoming common cause of visual impairment due to better neonatal care and advancement in technology. CVI is characterized by visual malfunction due to the retrochiasmal and visual association pathway pathology. The visual malfunction can present in any combination and any severity in the setting of developing brain functions. Higher centers damage may lead to cognitive dysfunction. Most common cause of CVI is hypoxic ischemic encephalopathy, due to reduced blood flow in immature brain blood vessels in watershed zones. Early identification of impairment and early intervention help these children to achieve higher level of vision. Customized and integrated approach needed between ophthalmologist, paediatrician and other interventional professional. Counselling of parents also have very important role in the treatment.



How to cite this article:
Swaminathan M, Patial Y. Cerebral visual impairment.TNOA J Ophthalmic Sci Res 2018;56:244-246


How to cite this URL:
Swaminathan M, Patial Y. Cerebral visual impairment. TNOA J Ophthalmic Sci Res [serial online] 2018 [cited 2023 Jan 27 ];56:244-246
Available from: https://www.tnoajosr.com/text.asp?2018/56/4/244/252488


Full Text



 Introduction



The term CVI stands for cerebral visual impairment and commonly also referred as cortical visual impairment or neurologic visual impairment. CVI is preferred over cortical visual impairment because cortex is rarely involved in isolation. The term neurologic visual impairment includes both cortical visual impairment and cortical blindness. Previously, it was referred to as cortical blindness, but blindness can be misleading as these children are not completely blind. In developing country such as India, because of advancement in technology and better neonatal care, CVI is becoming one of the most common causes of visual impairment in children as in the developed country. Prevalence of visual impairment in developed country varies from 10 to 22 cases/10,000 birth in children <16 years of age, while reported around 10/10,000 birth in developing country.[1] In an African study, 47.7 of children with cerebral palsy found to have CVI, while in an Indian study, only 28% of cerebral palsy patient found to have CVI.[2],[3] This article will give you overview about what does CVI mean and how to identify it and manage it.

 What is Cerebral Visual Impairment?



Vision is a complex function of the brain which involves eyes, visual pathway, and higher cortical center. A large portion of the brain is involved in vision. Many authors have defined CVI and the definition is still evolving. CVI is characterized by visual malfunction due to the retrochiasmal and visual association pathway pathology.[4],[5]

The visual malfunction can present in any combination and any severity in the setting of developing brain functions. Injury to retrochiasmal pathways may affect visual acuity, color vision and contrast sensitivity, visual fields, and perception of movements (dyskinetopsia). Defects in higher visual center may affect cognitive functions, main cognitive pathways are the dorsal stream (connecting the occipital cortex, the posterior parietal lobes, the motor cortex, and the frontal cortex) and the ventral stream (connects the occipital lobes and the temporal lobes). The dorsal stream dysfunction affects visual scene processing, coordination of body movements, and focusing in particular area of visual scene, which can lead to optic ataxia (impaired visual guidance of movement), apraxia of gaze (inability to move the eye to target), and limited capacity to simultaneously see many items at one time. These are the triad of Balint's syndrome. Ventral stream dysfunction affects identification of people and objects, route finding, and visual memory which can lead to prosopagnosia (impaired recognition of faces despite adequate vision) and topographic agnosia (profound difficulty in route findings particularly in new places). Other visual disabilities, which these children exhibit, are eye movement disorder such as strabismus, nystagmus, unstable fixation, inaccurate fast eye movements, deficit of smooth pursuit movements, and paradoxical eye movements. Strabismus can impair binocular vision or can lead to amblyopia. These children also have hypoaccommodation which may or may not be associated with hyperopia.

Along with visual malfunction these children may or may not have cerebral palsy leading to delayed motor and speech development.

Causes

Common causes of CVI in neonates and infant are listed below:

Hypoxic-ischemic damageNeonatal hypoglycemiaMetabolic diseaseCentral nervous system infectionStrokeTraumatic brain injuryStructural brain anomaliesHydrocephalusChromosomal aberrationsSeizuresMaternal intake of drugs and alcohol.

Associated conditions

PrematurityCerebral palsyHydrocephalusWilliams syndromeAutistic spectrum disorders.

Mechanism of injury

Most common cause of CVI among newborn infants is reduced level of oxygen to the brain. Reduced blood flow in immature brain blood vessels in watershed zones cause focal tissue damage, especially periventricular white matter damage leading to periventricular leukomalacia. Other causes such as low blood sugar, metabolic disorders, respiratory distress, asphyxia, and brain hemorrhage all affect the amount of oxygen that reaches the visual centers to brain and can cause brain tissue injury. Trauma and infection can cause focal brain tissue injury.

Differential diagnosis

Differential diagnosis of abnormal visual behavior

CVIDelayed visual maturationHigh refractive errorAbnormal retinal developmentOptic nerve abnormalitiesOculomotor apraxia.

 Identification



In children, the brain is still developing, so aim of the evaluation should be early identification of CVI. For early identification, integrated approach is needed between ophthalmologists, pediatricians, and other interventional professionals. As assessment of these children is time-consuming and these children have associated cognitive difficulties, assessments should be done in special clinics by the trained professionals. Assessment starts from the following:

History taking from parents or caregiversThe assessment of the visual function such as visual acuity, perception of color, ability to see contrast, and central visual fieldRefractionVisual behavior assessment and evaluation.

An author from Belgium has developed a questionnaire for identification of children at risk of CVI. Parents have to fill out the questionnaire and this score is correlated with examination and testing result.[6] Later, Roman-Lantzy developed an evaluation scale called CVI range which included both parents' assessment and the evaluation process.[7] The CVI range usage and its reliability was evaluated by Newcomb.[8]

Why it is important to identify the features of CVI? Because these visual malfunctions can be easily overcome by simple environmental modification and can help the child to be a part of mainstream and help to perform academically well.

According to the Philip and Dutton,[5] practically these children fall into three groups:

With profound visual impairmentWith impaired but functionally useful vision as well as cognitive and often motor challengesWith impaired but functionally useful vision and who work at or near the expected academic level for their age.

 Investigation



In children with CVI, magnetic resonance imaging (MRI) brain can be normal or may show changes such as periventricular leukomalacia, encephalomalacia, and gliosis. There is no direct correlation between the MRI findings and presence of CVI. Recently, functional MRI and diffusion tensor imaging MRI modality also used for diagnosis in children with CVI.

 Management



Early identification of impairment and early intervention help these children to achieve higher level of vision; the authors have reported that 95% of children with CVI developed higher level of vision within period of 3.7 years after receiving a program of visual intervention. Various combination of impairment with any degree can be present in these children. Hence, the principles of management should be as follows:

Identify individual children visual impairmentCustomize the strategy for treatment or rehabilitation for individual childrenCounseling and training of parents or caregivers by a teacher for visually impaired or occupational therapist trained in low vision or an early intervention specialist.

The visual intervention for these patients can be given in phases, starting from building visual behavior and then vision in play which stimulates motivation and action and finally to expand child's ability to use his or her vision in order to solve problems for daily activities. To build visual behavior, enhancing the environment by simple modifications such as using favorite color of children in toys and objects of child's interest and using contrast background or painting play area of child according to his favorite color. The cognitive dysfunctions in these children disturb communication and social interaction. By teaching communication skills to infants, children and parents, we decrease negative attitudes due to the misinterpretations toward these children and can improve social interaction. Additional therapies such as occupational, physical, speech, and other therapies may be required according to associated disabilities. While everyone has a right to education, health-care professional faces the big problem to decide whether to send child to normal school or special school, especially in children with multiple disabilities. Even though sometimes they can go to normal school, but higher education is always a difficult decision. Detailed management of CVI is beyond the scope of this article.

 Conclusion



CVI is an important cause of vision impairment in children. Early identification and early intervention can help many of them to achieve higher level of vision. For early identification, integrated approach is needed. Identification of individual problem and customization of intervention such as simple environmental modification can be done for treatment. Parents and caregivers play the most important role in giving intervention, so their counseling and training is important.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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