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 Table of Contents  
MAJOR REVIEW
Year : 2020  |  Volume : 32  |  Issue : 1  |  Page : 27-35

Cerebral visual impairment in children


Department of Ophthalmology, Kerala Health Services, District Hospital, Palakkad, Kerala, India

Date of Submission01-Mar-2020
Date of Acceptance02-Mar-2020
Date of Web Publication17-Apr-2020

Correspondence Address:
Dr. Geetha V.K.P.
Department of Ophthalmology, District Hospital, Palakkad - 678 001, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kjo.kjo_25_20

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  Abstract 

Cerebral visual impairment has gained importance due to increased survival of extremely premature babies. It encompasses visual processing dysfunctions due to disorders of the retrochiasmal pathways and visual association areas. This review describes the physiology of visual processing, clinical approach to children with Cerebral Visual Impairment, and principles of intervention. Functional vision assessment and vision intervention strategies are given emphasis. We have to ensure that these children are able to use vision for learning, for social interaction, and mobility. A literature review was undertaken using Medline and PubMed.

Keywords: Cerebral visual impairment, functional vision assessment, vision intervention


How to cite this article:
Geetha V.K.P.. Cerebral visual impairment in children. Kerala J Ophthalmol 2020;32:27-35

How to cite this URL:
Geetha V.K.P.. Cerebral visual impairment in children. Kerala J Ophthalmol [serial online] 2020 [cited 2020 Aug 12];32:27-35. Available from: http://www.kjophthal.com/text.asp?2020/32/1/27/282654




  Introduction Top


Cerebral visual impairment has recently become the most common cause of visual impairment in children in developed countries.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10] It is emerging as a major cause of visual impairment in our country also. This is probably due to the management of treatable conditions such as congenital cataract, congenital glaucoma, and ROP.[11] There is better survival of children who have sustained severe neurological damage during the perinatal period.[12],[13],[14] Due to a better understanding of the condition, more cases are diagnosed and reported, which has led to the reported increase in number of Cerebral Visual Impairment (CVI) cases.[15] In a recent study from Hyderabad, it was found that CVI was the most common cause of profound visual impairment in <3 years of age (33%).[16]

Cerebral visual impairment is deficiency in the function of vision due to damage to or malfunction of visual pathways and visual centers in the brain, (specifically posterior to lateral geniculate body) including the optic radiations, the occipital cortex, and the visual associative areas, which may be accentuated by associated disorders of the control of eye movements.[17] The term CVI was introduced in the 1990s to describe deficits of vision and visual perception in children.[18] Both the terms “cerebral” and “cortical” visual impairment have been used interchangeably by some authors. However, a more contemporary view suggests the involvement of subcortical structures, optic radiations other white matter pathways, and higher order visual processing areas, and the term “cerebral visual impairment” is more appropriate.[19] In the US, the term Cortical Visual Imapairment continues to be in common use.

Cerebral visual impairment and ocular visual impairment have few differences, as explained in [Table 1].[20]
Table 1: Differences between cerebral visual impairment and ocular visual impairment


Click here to view


Children with CVI fall into the following three groups:

  1. Those with profound visual impairment
  2. Those with impaired but functionally useful vision, as well as cognitive and often motor challenges
  3. Those who have impaired but functionally useful vision and who work at or near the expected academic level of their age.



  How Does Our Brain See? Top


[Figure 1] shows the three visual brain areas and the connecting dorsal and ventral networks, where visual processing takes place.
Figure 1: Three visual brain areas and the connecting dorsal and ventral networks (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg10))

Click here to view


The retinal photoreceptors convert light energy into electrical impulses which are transmitted to the visual cortex where primary processing takes place for visual acuity, color, contrast sensitivity, and visual fields. From the occipital lobe, this information is passed to inferotemporal lobe through ventral stream and posterior parietal lobes through dorsal stream. In the inferotemporal lobe (the visual library), visual recognition of faces, objects, shapes, and routes takes place by matching the images sent by occipital lobe with the images stored in the temporal lobe. Hence, focal damage of the inferotemporal cortex and ventral stream impairs visual recognition of faces and objects and route finding. In the posterior parietal lobes (visual map) analysis of visual scene, giving attention to object of interest, creating a mental three dimensional map of the external world and visual guidance of body movements takes place. Focal dorsal stream damage, therefore, leads to impaired visual guidance of movement (optic ataxia), inability to process multiple items within the visual scene (simultanagnosia), inability to process multiple sensory inputs such as vision hearing at the same time, inability to move the eyes to look at items that have not been mapped (apraxia of gaze) inability to locate the direction of sound and visual field impairments.

For example, take a simple act of catching a ball. The analysis of details of the ball in terms of clarity, contrast, and color is accomplished in the occipital lobes. The recognition of its identity is achieved by the temporal lobes. Its initial location and form are mapped in the parietal lobes. Its vector is appreciated by combined activity in the middle temporal and posterior parietal lobes. The predicted location of the ball is provided by prior experiential learning including oculomotor, or perceptual and spatial experience mostly in the frontal and parietal lobes. The requisite temporary nonconscious internal 3D emulation of the visual scene is created by the occipital and posterior parietal lobes. The moment to moment 3D coordinates of the shape and location of ball reach the motor cortex which, supported by the timing system in the cerebellum, the overall balance system, and the reflex motor support systems in the brainstem and thalamus, brings about the requisite finely tuned action to catch the ball, while the choice of catching the ball was made in the frontal lobes. Disruption in any part of this complex visuomotor system, disturbs this mundane act, rendering it difficult or impossible.[21]


  Common Causes of Cerebral Visual Impairment Top


The common causes of CVI are the following.[20]

  • Hypoxic ischemic encephalopathy - Periventricular white matter damage or Periventricular Leukomalacia is the commonest preterm neurological insult. This Could be due to vulnerability of immature brain blood vessels in watershed zones, leading to reduced blood flow causing focal tissue death.


  • Neonatal hypoglycemia
  • Hydrocephalus
  • Focal brain lesions like stroke, hemorrhage, focal tumors
  • Brain injury due to accidental or non accidental trauma
  • Brain infections: meningitis or encephalitis
  • Brain malformation



  Behaviours Typical to Children With Cerebral Visual Impairment Top


Variation in visual functions is very common in CVI. This may be due to fatigue or emotional stress in the child or due to visual clutter, other sensory stimuli, or familiarity of the object. Visual field defects hemianopias or lower quadrantanopias are common. Color may appear washed out. Sometimes, color preference may be there (red/yellow). Face or facial expressions may be difficult to recognize. There may be difficulty in recognizing the shapes, size, letters, numbers, line direction, and length. Route recognition may be difficult. Another characteristic feature of dorsal stream dysfunction is simultanagnosia, i.e. limited capacity to pay attention to the several details of the scene. Optic ataxia (impaired visual guidance of movement through the visual world) also may be there. Crowded places may be frightening. Fast moving objects may not be seen or may appear to be on collision course, when actually they are not (looming). Only few elements of visual scene may be visible due to field defect, simultanagnosia, or attentional loss which disturbs search, reading, or copying. Eye contact may be abnormal. The child seems to look at the hairline when there is a central scotoma. The child may not be able to look at the face and listen to the voice simultaneously.

A child usually has less than one-third of the 60–80 atypical visual processing functions. Each child has their own unique pattern of vision. Every single component is affected in different proportions and different degrees in every single child-like a kaleidoscope!


  How to Approach a Child With Cerebral Visual Impairment? Top


It should be a trans-disciplinary assessment involving pediatrician, pediatric neurologist, ophthalmologist, physiatrist, neuropsychiatrist and ENT surgeon. In the first visit, ophthalmologist should be able to establish a diagnosis of Cerebral Visual Impairment.

CVI should be suspected in any child whose visual functioning cannot be explained by the ophthalmological findings, more so if the child is preterm/has a neurological ailment/has a history of an eventful perinatal period. A close differential diagnosis of CVI in young children is delayed visual maturation.

Comprehensive eye evaluation to look for any treatable ophthalmological problems

Each child should undergo comprehensive eye examination, which includes assessment of:

  1. Head posture due to ocular problems like congenital nystagmus, due to poor neck control or spasticity, or due to simultanagnosia
  2. Facial symmetry
  3. Visual acuity by method which is appropriate for age, for distance and near
  4. Dry and cycloplegic refraction (atropine 1% eye ointment <in 5 years, homatropine 2% eye drops in >5 years, cyclopentolate should be avoided in all) various studies show that between 10% and 60% of children with CVI have significant refractive errors requiring spectacle correction.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11] The most successful and easy intervention in CVI children is spectacle correction, and it should be done at the earliest
  5. Dynamic retinoscopy to assess the child's ability to accommodate. It is reported that 57% of children with cerebral palsy (especially spastic diplegic cerebral palsy) and 80% of children with Down's syndrome have reduced ability to accommodate.[22],[23],[24]


Methods of the assessment of accommodation:

  1. Observe pupil, as the child switches attention from a distant object (3 metre distance) to near one (20 cm from face). If the pupil does not constrict as child shifts focus from distant to near, then accommodation is likely impaired
  2. If a child has poor visual awareness, one can note retinoscopy reflex in dark and then show an illuminated toy close to the child's face and again note retinoscopy reflex. If reflex changes from 'with' to 'against', it indicates that child can accommodate.


Due to a lack of accommodation in CVI, even low hyperopic refractive errors may become significant and need to be corrected. One must account for impaired accommodation while prescribing glasses. If the fitting of frames is not appropriate, the discomfort prevents the child from wearing glasses. It is important to convey to the family that the benefit of glasses may not be seen immediately. It was found that almost 50% of children with CVI had undiagnosed significant refractive error, 49% had squint, 12% had hypoaccommodation, and 4% had cataract. None of them had received a complete eye examination and consequently did not get treatment.[25] Two common causes of lack of eye contact at the age of 3 months are high hyperopia or weak accommodation. Both cause blur in the visual image, which can be corrected by near vision glasses.[26]

Counselling

During counselling, we should focus on child's strengths and convey that the condition is caused by neural damage which cannot be undone, yet consistent repeated experiences with successful use of residual vision can encourage the brain to find other ways to make sense of what ever visual information is received. It is very important to empower the parents with the necessary knowledge about child's vision, how to arrange the environment, and how to incorporate the use of vision in daily routine of the child.


  Functional Vision Assessment Top


After correcting the treatable ocular conditions, child is called for a second visit to assess the functional vision. During visual function assessment, we assess the thresholds for different parameters of vision such as visual acuity, contrast sensitivity, color vision, and visual fields which is done in a static controlled environment for each eye separately. On the contrary, functional vision assessment is done binocularly to understand how does a person use vision to perform tasks of daily living in a dynamic environment. A detailed functional vision assessment profile enables optimal habilitation, or rehabilitation through: 1. adaptation to render information perceptible, and accessible. 2. substitution to provide alternative strategies and 3. training to attain improvements through neuroplasticity.[27]

History taking

For High functioning CVI children, elicit information about visual behavior using structured clinical question inventory (CVI inventory developed at the Royal Hospital for Sick children, Glasgow by Dr. Gordon N Dutton)[28] as a guide to ensure that key issues are not omitted. In children with profound CVI in whom visual acuity is <6/60 another visual skill inventory[29] can be used.

The examination room in the busy out patent department is unsuitable for these assessments. It is desirable to have a quiet room without clutter. The child should be positioned in such a way to facilitate maximum use of vision. It is desirable to have a facility to change illumination in the room. The tests used should help us design a habilitational plan. The results of the tests should be such that we can explain to parents in a language they can understand and apply.

In profound CVI, the following tests are useful to assess functional vision.[30]

Facial communication distance

One should go close to child with a silent smile and look for distance at which child takes notice of the face approaching the child. Then move slowly away and again try to estimate at which distance child consistently takes cognizance of the face. Parents should be explained about this and advised that whenever they communicate with child, they need to be within this distance.

Preferential looking (PL) tests – As per history, if there is some evidence of vision, one of the preferential looking tests, Teller acuity cards, or Lea paddles, as shown in [Figure 2],[31] can be used. These tests are based on the principle that when presented with a homogeneous and a patterned stimulus, an infant prefers to look at a patterned stimulus.
Figure 2: Lea Paddles (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 56))

Click here to view


Special considerations in relation to Cerebral Visual Impairment

  1. Saccadic eye movement may be affected in children with CVI; hence, one may not be able to see that movement
  2. Neck control may be delayed; hence, many may not be able to turn their heads toward the grating
  3. The grating may be lying the nonseeing part of the visual field
  4. The presence of squint and nystagmus may confound the observations.


In such a situation, one should look for other clues for response such as change in facial expression, stilling of body movements, slowing down of respiration, slowing down of roving eye movements, eye widening, just a glance toward the pattern, and without sustained fixation. Sometimes, seeing and turning away can be a sign of seeing, if the child consistently looks away from the stimulus. When squint or nystagmus is present try presenting cards vertically.

These tests help parents to understand the optimal line thickness and separation between lines that the child can appreciate. While explaining the result to the parents, one should explain the line thickness, compared to that of their fingers as shown in [Figure 3],[30] that what the child could appreciate and at what distance.
Figure 3: Comparison of fingers with Lea Paddles (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 57))

Click here to view


When the child does not respond to the above mentioned PL tests, we can try Puppet faces, as shown in [Figure 4],[32] which are more child friendly because human face is a stronger stimulus.[32] If the child is unresponsive to above tests, playing with the child for a few minutes using a cloth glove in which the tactile features coincide with the visual ones, as shown in [Figure 5],[33] can make the child interested in the test.[33]
Figure 4: Puppet faces to assess vision response in low functioning Cerebral Visual Impairment (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 57))

Click here to view
Figure 5: Cloth glove in which the tactile features coincide with the visual ones (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 58))

Click here to view


Mirror test – Start from close to the child's face, grab child's attention to his/her own image in the mirror and then slowly move away till the child loses eye contact with mirror image. This distance acts as a rough estimate of child's visual sphere and has been shown to correlate with TAC.[34]

Visual field We find confrontation method useful for assessing visual fields in children with CVI using interesting toy, Puppet faces[32] or Lea wand[31] and leg rise test for the extreme lower field. If the child does not cooperate for these formal tests, we assess visual fields through play situations.

Contrast sensitivity

Assessed with the help of Hiding Heidi low contrast face test, as shown in [Figure 6].[31] which is designed for assessment of low contrast information in communication situations. One should hold a blank card and a high contrast Hiding Heidi card overlapping and then move both apart at equal speed to check child's response. If the child is able to see the picture in the card, the child will mimic the smile in the card even at the early age of 12 weeks. If the child is able to see the test can be repeated with cards of lower level of contrast. By presenting the test at different distances, it is possible to assess how close the people should be in communication situation so that the infant can perceive faces.
Figure 6: Hiding Heidi low contrast face test (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 62))

Click here to view


Color preference can be tested using colored balls. If child consistently responds to any particular color, we can take advantage of that using the same color while introducing a new object to the child. We can use those colors in child's environment and daily routines.

  • Latency for visual attention:This means how long does it take for the child to take visual cognizance of a stimulus shown. It may take up to 30–45 s


  • Span of visual attention:Once seen, for how long is the child engaged with the stimulus visually? In children with CVI, this could be very brief like 1–2 s due to their limited neuronal circuitry and issues of higher attentional mechanisms
  • Saccades and pursuits: For testing pursuits, we see if the child can follow a slowly moving target smoothly. For testing saccades, we show two attractive targets and illuminate them alternately, separated by a distance. Saccades are important for us to scan the environment (voluntary saccades) and particularly important while reading (reflex microsaccades)
  • Hand eye coordination: This can be tested by asking the child to stack the rings, put things inside a container, pick-up a toy from the floor.



  Cognitive Visual Assessment Top


In high functioning CVI, when the child has normal or near normal visual acuity, but yet has issues with using his vision in day today activities, we should suspect cognitive visual dysfunction and assess dorsal and ventral streams by following tests.

Lea Puzzle[31] [Figure 7]: Explain the test to the child first, start with the color side. Give one shape at a time and ask where to put it – if child could match color and shape; it means ventral stream functions normally. The way child grasps the symbol, orients it according to the slot on the puzzle and the ease with which he puts it inside that slot, tells about the way dorsal stream functions. If child could do it well, make it slightly complex by changing the orientation of the puzzle. If child could do well with this too, then use the reverse side of the puzzle, which is in black and white. Next, we can keep all the shapes together and ask the child to pick-up one symbol. This tests for “analysis of multiple objects visually” by dorsal stream.
Figure 7: Lea Puzzles (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 65))

Click here to view


Lea mail box test[31] [Figure 8]: Here, the child has to post the white card through the slit in the yellow circular disc, like posting a letter into post box. Explain the procedure to the child. Give the white card and see how he grasps it. Look for separation between fingers, the way hand approaches the card, does it overshoot or undershoot (dorsal stream function). See how child changes the orientation of the card as per the orientation of the slit (understanding the direction of orientation is function of ventral stream and aligning the card as per that is dorsal stream function). See how does he post the card visually, or touches the yellow disc, takes tactile clues.
Figure 8: Lea mail box (Printed with permission from Cerebral Visual Impairment user manual. Editors Niranjan Pehre, Arun Singh. Rashtriya Bal Swasthya Karyakram, Government of India, 2019 (Pg 66))

Click here to view


Object sorting test: Here, we mix-up objects of different shapes and colors in a basket and ask the child to pick-up one of them. See if child directly picks up the desired object or takes them out one by one, sees what it is and then takes the next one. This suggests dorsal stream dysfunction. Look for the reaction time-does the child pick-up things reflexly or has to exert sufficient attention and time.

Motion Perception: The examiner shows his fingers and asks the child to count them. Then he slowly starts waving hand, asking the child to count fingers, slowly increasing speed of hand till child cannot count fingers. If the slightest movement of hand makes child unable to count fingers, then child has severe issue with motion perception (dyskinetopsia).

Play situations: roll a ball to child on the floor and see if he tracks the movement of the ball. The inability to appreciate the movement of ball may be indicative of dyskinetopsia.

For simultanagnosia:ask the child to describe what is he able to see around him in the room without taking unduly long time.


  Intervention Top


The following framework of thinking is useful in making a habilitational plan for a child with CVI:

Why, how, and what?

Why is it happening? To find an answer, the following details help:

The underlying neurological issue, which part of the visual brain, is affected? Any Treatable issues? Thresholds of vision as per functional vision evaluation.

How can we work around it? How can we make-up for the element that is missing in the vision processing? For example, A child being unable to reach out accurately due to optic ataxia is basically living in a two dimensional world. To complete that missing information, he needs extra nonvisual clues like touch/sound.

What to do? Once we understand why it is happening and how to work around it, then it is easier to think what exactly to do for a particular task with resources available in child's surrounding.

The difference between vision stimulation and vision intervention.

Vision stimulation refers to passively watching high contrast visual stimuli in a dark room. This has little value as it does not develop the adaptive capacity of the brain.[35]

Vision intervention, on the other hand, is a dynamic and interactive approach. The instructor chooses specific meaningful stimuli found by assessment, makes adjustments seeing child's reaction, and helps the child to learn. The goal of vision intervention is to create an opportunity to gain and give meaning to visual information already available. Once the child starts to learn that vision is a valuable source of information, increased periods of alertness manifest. The child needs support to recruit and use visual system at this point because this does not come naturally.[36]


  Principles of Intervention Top


  1. Understand the capacity and start well within it. Know the limits, staying within them using alternatives, extend the limits by changing one parameter at a time
  2. Prepare the child with a hug, jumping, bouncing which can help in activating their attentional and visual system
  3. Ensure that the child's posture is comfortable to enable him to use vision
  4. Prime about the object beforehand. Let the child have a mental image which they can use when they search visually
  5. Use descriptive “radio language.”[37] Use words which would vividly explain object without having to see it, just like radio commentators do
  6. Always assist the child. For a response may need to wait till 15–30 s. May need some help such as movement of the object, or some cue
  7. Presentation should be slow and simple. Start with simple familiar objects, in an environment without competing stimuli, at child's own pace
  8. Use multisensory stimulation. When vision is poor, the brain needs links with other senses such as touch, sound, and smell to form meaningful memories
  9. Communication: Never leave the child unattended for long periods as they learn best through interaction. Enhance facial contrast using makeup that matches line thickness and contrast. Stay within child's visual sphere. Provide tactile inputs by letting the child touch the face
  10. Need for interdisciplinary care. Around 60% of children with CVI have delay in one or more areas of development.[25] Hence, it would be ideal if the therapist understands child's vision and provide all therapies under one roof
  11. Sensory tent in profound CVI, this will eliminate clutter, so that child can focus on single stimulus presented[38]
  12. Some apps on i-Pad like Big Bang Patterns, Color Dots, are found to be useful for promotion of visual attention, visual tracking and eye-hand coordination. In them the parameters of the presentation can be modified to match the thresholds of visual processing of the child. These apps are not substitute for real objects which can be felt and experienced. In children with very low visual attention these form a “warm up” for a session.[30]
  13. Children with CVI struggle to look and listen at the same time. They need words to be spoken one at a time and clearly. When a word is used to label something that is not seen, it does not make sense, and it can affect learning. It can look like a learning delay, but in fact, they have a language delay due to their CVI
  14. Always try to infuse vision into day-to-day routine activities. Then the intervention becomes an ongoing experience and routine activities become meaningful learning experiences
  15. Children with profound CVI tend to gaze at bright light. This behavior can be made use of in light box activities to arouse visual curiosity initially and later to improve visual discrimination and efficiency[39]
  16. When a child has cognitive visual dysfunction potential strategies which can be used to help him in specific issues are developed by Dr. Gordon Dutton.[40]


The key for effective management of CVI is regular interaction between child, caregivers, and professionals taking care of the child. We have to fully understand every aspect of limitations imposed by CVI so that we can see the world through his eyes and ensure that everything you provided can be understood by the child. The new concept of neuroplasticity (the ability of the brain to develop new neuronal connections in response to stimuli or experiences, which is greatest for visual stimuli <7 years of age) can lead novel training programs depending on the nature and degree of visual dysfunction.[41]

Let's conclude with a statement of Dr. Gordon Dutton (a personal communication to the author). “ All conditions that are lifelong from the time of onset become alternative state of normality. While children with CVI may not be typical, they are normal unto themselves and to their families. They need to be empowered in their normality. We need to recognize their strengths and abilities so that they would be motivated and happy and able to make best use of their lives which in turn would neuroplastically develop their brains”.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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