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Vision in a Child With Hydranencephaly

In this section of the website you will find information contained in the book "Caring For Your Child With Hydranencephaly" Part 4: Resources in Caring for Your Child.

In some instances I will include the text as it appears in the book and in others will just give you the link to where the information can be found. Please note that none of the information in this section is my own. It is taken from the websites mentioned at the top of each article.

Vision and it's development are big areas in our children's lives.

Cortical Visual Impairment
This condition is very common in children with Hydranencephaly. It means that although there is nothing wrong with the eyes itself, the brain is unable to tell the eyes what they are seeing. Children with CVI aren't totally blind. They see some colors better than others, their vision may come and go, and change from day to day. Personal experience: We were originally told that Kayda had no optic nerve. Three years later that same Dr became convinced that she could see. She now sees and often clearly understands objects up to 4 ft away. Her vision does vary from minute to minute. In all the information that I've read on CVI the common thread seems to be that progress is possible.

Cortical Visual Impairment
http://66.147.244.207/~blindbab/wp-content/uploads/2010/08/Fact-Sheet-CVI-REVISED-FINAL.pdf

Definition
Cortical Visual Impairment (CVI) is a temporary or permanent visual impairment caused by the disturbance of the posterior visual pathways and / or the occipital lobes of the brain. The degree of vision impairment can range from severe visual impairment to total blindness. The degree of neurological damage and visual impairment depends upon the time of onset, as well as the location and intensity of the insult.

It is a condition that indicates that the visual systems of the brain do not consistently understand or interpret what the eyes see.

The presence of CVI is not an indicator of the child's cognitive ability. 

Cause
The major causes of CVI are asphyxia, perinatal hypoxia ischemia ("hypoxia": a lack of sufficient oxygen in the body cells of blood; "ischemia": not enough blood supply to the brain), developmental brain defects, head injury, hydrocephalus, and infections of the central nervous system, such as meningitis and encephalitis.

Characteristics
Initially, children with CVI appear blind. However, vision tends to improve. Therefore, Cortical Visual Impairment is a more appropriate term than Cortical Blindness. A great number of neurological disorders can cause CVI, and CVI often coexists with ocular visual loss so both a pediatric neurologist and a pediatric ophthalmologist should see the child.

The diagnosis of Cortical Visual Impairment is a difficult diagnosis to make. It is diagnosed when a child has poor or no visual response and yet has normal pupillary reactions and a normal eye examination. The child's eye movements are most often normal. The visual functioning will be variable.

The result of an MRI (Magnetic Resonance Imaging) in combination with an evaluation of how the child is functioning visually, provide the basis for diagnosis.

Behavioral / Visual Characteristics
Children with CVI have different abilities and needs. The presence of and type of additional handicaps vary. Some children have good language skills and others do not. Spatial confusion is common in children with CVI because of the closeness of the occipital and pariental lobes of the brain. Habilitation should be carefully planned. A full evaluation by a number of professionals is essential. The evaluation team could include: teachers (of the visually impaired or severely handicapped), Physical Therapists (PT's), Occupational Therapists (OT's), Speech Therapists, and Orientation and Mobility Specialists.

Common characteristics of visual function demonstrated by children with CVI:

  • Vision appears to be variable: sometimes on, sometimes off; changing minute by minute, day by day.
  • Many children with CVI may be able to use their peripheral vision more effectively than their central vision.
  • One third of children with CVI are photophobic, others are compulsive light gazers.
  • Color vision is generally preserved in children with CVI (color perception is represented bilaterally in the brain, and is less susceptible to complete elimination).
  • The vision of children with CVI has been described much like looking through a piece of Swiss cheese.
  • Children may exhibit poor depth perception, influencing their ability to reach for a target.
  • Vision may be better when either the visual target or the child is moving.

The behaviors of children with CVI reflect their adaptive response to the characteristics of their condition:

  • Children with CVI may experience a 'crowding phenomenon" when looking at a picture: difficulty differentiating between background and foreground visual information.
  • Close viewing is common, to magnify the object or to reduce crowding.
  • Rapid horizontal head shaking or eye pressing is not common among children with CVI.
  • Over stimulation can result in fading behavior by the child, or in short visual attention span.
  • The ability of children with CVI to navigate through cluttered environments without bumping into anything could be attributed to "blindsight", a brain stem visual system.
  • Children are often able to see better when told what to look for ahead of time.
  • Children with CVI may use their peripheral vision when presented with a visual stimulus, appearing as if they are looking away from the target.
  • Some children look at an object momentarily and turn away as they reach for it.

Myths
The following statements are not true, according to current knowledge in the field:

  • Children with CVI are visually inattentive and poorly motivated. All children with CVI will have cognitive deficits.
  • CVI is not a true visual impairment.
  • Children with CVI are totally blind.
  • Children whose visual cortex is damaged are Cortically Blind.

Teaching Strategies

  • A great deal of energy is needed to process information visually. The child might tire easily when called upon to use his visual sense. Allow for intermittent "break" times.
  • Positioning is important. Keep the child comfortable when vision use is the goal in order that "seeing" is the only task.
  • Head support should be provided during play or work sessions, to avoid involuntary shifting of the visual field.
  • Try many different positions to find the one in which the child feels most secure. Infants and toddlers will demonstrate when and where they see best by their adaptive behaviors.
  • If the child needs to use a lot of energy for fine motor tasks, work on fine motor and vision separately, until integration of the modalities is possible.
  • The simpler, more constant and more predictable the visual information, the better the child with CVI is likely to deal with it. Keep toys and environment simple and uncluttered.
  • Use books with one clear picture on a contrasting simple background.
  • Use familiar/real objects (bottle, bowl, plate, bath toy, diaper, cup, spoon, favorite toy) one at a time. Familiarity and simplicity are very important.
  • Since the color system is often intact, use bright fluorescent colors like red, yellow, pink, and orange. Colored mylar tissue seems to evoke visual responses.
  • Repetition is very helpful: use the same objects and same process each time to provide familiarity and security for the child. Familiarity breeds response.
  • Look for toys and activities that motivate the child.
  • Vision is often best stimulated when paired with another sensory system. For example, auditory cues from the handling of mylar may help attract the child's attention.
  • Introduce new and old objects via touch and verbal description.
  • Try different lighting situations to assess optimal conditions for viewing. Try locating a light source behind, and/or to the side of the child.
  • Try moving the target that you want the child to see. Try different visual fields.
  • Allow lots of time for the child to see and to respond to what is being seen. Learn to interpret each child's subtle response cues: such as changes in breathing patterns, shifts of gaze or body position, etc.

"When a child with CVI needs to control his head, use his vision, and perform fine motor tasks, the effort can be compared to a neurologically intact adult learning to knit while walking a tightrope."

 Resources
1."Observations on the Habilitation of Children with Cortical Visual Impairment" Groenveld, M.; Jan, J.E.; Leader, P., Journal of Visual Impairment and Blindness, January, 1990.

2. Visual Behaviors and Adaptations Associated with Cortical and Ocular Impairment in Children," Jan, J.E.; Groenveld, M.; Journal of Visual Impairment and Blindness, April 1993, American Foundation for the Blind.

3.Video: "Issues in Pediatric Ophthalmology: Cortical Visual Impairment (1994)," Child Health and Developmental Media, Inc., 5632 Van Nuys Blvd., Suite 286, Van Nuys, CA 91401

4."Cortical Visual Impairment in Children, " Good, W; Jan, J.E.; Luis, D. (1994) Survey of Ophthalmology. 38:4: 351-364.

ACKNOWLEDGMENTS
Julie Bernas-Pierce, Editor
Janice Polizzi Home Counselors
Colette Altmann Dennak Murphy
Barb Lee Dr. William Good
Dr. Creig Hoyt Ann Silverrain
Off to a Good Start Program

Many of the children with Hydranencephaly are also thought to have ONH. 

Optic Nerve Hypoplasia
http://66.147.244.207/~blindbab/wp-content/uploads/2010/08/Fact-Sheet-Optic-Nerve-Hypoplasia.pdf

Definition
Optic Nerve Hypoplasia (ONH) refers to the underdevelopment of the optic nerve during pregnancy. The dying back of optic nerve fibers as the child develops in utero is a natural process, and ONH may be an exaggeration of that process. ONH may occur infrequently in one eye (unilateral) but more commonly in both eyes (bilateral). ONH is not progressive, is not inherited, and cannot be cured. ONH is one of the three most common causes of visual impairment in children.

Causes
In most cases there is no known cause of ONH. Infrequently ONH has been associated with maternal diabetes, maternal alcohol abuse, maternal use of anti-epileptic drugs, and young maternal age (20 years of age or less), but these factors account for very few of the total number of cases. All races and socio-economic groups seem to be affected by ONH.

 Characteristics

  • ONH may occur by itself or along with neurological or hormonal abnormalities. Hormonal problems not apparent in early life may appear later.
  • Children with ONH demonstrate a wide spectrum of visual function ranging from normal visual acuity to no light perception. The effect on the visual field may range from generalized loss of detailed vision in both central and peripheral fields (depressed visual fields) to subtle peripheral field loss.
  • A high percentage of children with ONH have associated involuntary rhythmic movements of the eye (nystagmus). In most cases, the nystagmus is associated with significant bilateral reduced visual acuity.
  • ONH is a stable condition. Visual function does not deteriorate with time. A mild improvement in visual function may occur as the result of maturation processes of the brain. In some cases, reduced nystagmus may also occur.
  • Depth perception may be more severe if vision loss is great.
  • Mild light sensitivity (photophobia) may occur.

 Diagnosis
ONH is diagnosed by direct examination of the eye by an ophthalmologist. No current laboratory or radiographic tests will establish the diagnosis. Many infants who are diagnosed with Optic Nerve Atrophy are, in fact, children with ONH. Sometimes visual functioning can be predicted from the appearance of the optic discs. However, it is very difficult to predict visual acuity on this basis alone.

Visual And Behavioral Characteristics

  • The child's vision is characterized by a lack of detail (depressed field), but this lack of detail is not comparable to the blurred reduction in vision when a person removes her glasses.
  • In certain cases of ONH a specific field defect occurs. Children may not be aware of people or objects in the periphery.
  • Children with ONH may be unable to locate objects in space precisely due to a lack of depth perception.
  • Some children with ONH have mild photophobia. These children may squint, lower their head, avoid light by turning away, or resist participating in outdoor activities.
  • When one eye is affected more than the other, an ophthalmologist may recommend a trial of patching the stronger eye, since the visual loss may be due to amblyopia.
  • Some feeding issues are associated with hormonal problems. Lack of interest in eating may be due to absent or diminished sense of smell and taste. Children with ONH may have very restricted food preferences. Some children exhibit excessive lip smacking while eating.
  • Behaviors of some children with ONH may be due to associated medical conditions, such as inattentiveness and irritability due to low blood sugar levels (hypoglycemia).
  • The child with associated central nervous system problems may be easily distracted, quickly frustrated and act in a disorganized or an impulsive way.

Conditions Associated With Onh
Associated brain and hormonal abnormalities are common in children with nystagmus and bilateral severe vision loss, and are less common in cases where vision loss is mild or unilateral. Abnormalities include:

1. Midline anomalies of the brain: septo optic dysplasia (absence of the septum pellucidum and the corpus callosum), encephaloceles, anomalies of the ventricles, anencephaly, cerebral atrophy, and rarely, tumors.

2. Hormonal insufficiencies: thyroid, growth hormone, pituitary, adrenal, anti diuretic hormone (ADH).
Associated midline brain anomalies can be identified by either an MRI or CT scan. Hormonal insufficiencies require an examination by a specialist in hormonal disorders (pediatric endocrinologist). Children particularly at risk for having associated hormonal insufficiencies are those who had neonatal low blood sugar (hypoglycemia), had prolonged jaundice (hyperbilirubinemia), failed to grow normally (failure to thrive), have difficulty regulating body temperature in connection with viral illnesses, and/or had a CT or MRI scan showing an absence of tissue connecting the brain to the pituitary gland (the pituitary stalk).

Myths
The following statements are NOT TRUE according to current research:

  • ONH occurs in clusters due to use of pesticides in the environment.
  • The associated midline brain anomalies have a profound effect on the visual outcome and/or spatial orientation of these patients.
  • All mothers of children with ONH were drug users during pregnancy.

Teaching Strategies

  • Each child should receive medical monitoring and comprehensive, ongoing, functional and educational assessment.
  • Teachers need to increase the size, contrast, and lighting of materials for a child who has nystagmus and bilateral severe visual loss because of generally depressed fields.
  • When a specific field loss is identified, materials need to be presented within the child's visual field. The child should be encouraged to turn his head to look for people and objects outside his visual field.
  • A child with ONH needs the opportunity to develop learned aspects of depth perception through fine and gross motor activities, including container play, nesting and stacking, ball tossing and rolling, pouring activities, and lots of practice with stairs, slides, foam wedges for crawling, and cardboard box play.
  • The effects of light sensitivity can be minimized by adjusting lighting levels, wearing tinted lenses, and minimizing glare on surfaces.
  • A child with ONH often has other conditions that need to be considered when developing an individual education plan.
  • A child who is easily distracted, frustrated, disorganized, and impulsive may be helped by predictable physical environments, dependable daily routines, and limited distractions.
  • Slowing the pace of activities and providing predictable transition routines may help reduce resistant and irritable behavior.
  • Offering frequent snacks to children diagnosed with hypoglycemia may be helpful.
  • When a child does have feeding problems, parents and professionals need to agree on recommended strategies to create a positive feeding experience.
  • When a child has no functional vision, an approach that uses all the senses for learning is needed.
  • Evaluation by an instructor of Orientation and Mobility is essential in meeting the child's needs, due to loss of detail vision and vision field loss.

 Resources
Borchert, M.S. An Inside Look At Optic Nerve Hypoplasia Research - A Leading Cause of Infant Blindness, USC School of Medicine.

Hoyt, C. (1986). Optic Nerve Hypoplasia: A Changing Perspective. Transactions of the New Orleans Academy of Ophthalmology. Raven Press, New York.

Lambert, S. & Hoyt, C. (1987). Optic Nerve Hypoplasia. Ophthalmology. 32, #1, July, August, 1-9.

Marsh-Tootle, W.L. (1994). Congenital Optic Nerve Hypoplasia: A Symposium Paper. Optometry & Vision Science. 71; #3, 174-180. 

Tait, P. (1989). Optic Nerve Hypoplasia: A Review of the Literature, Journal of Visual Impairment and Blindness, April, 207-211.

Willnow, S. et al. (1996). Endocrine disorders in septo-optic dysplasia (De Morsier syndrome)-evaluation and follow up of 18 patients. European Journal of Pediatrics, 155; 179-184.

Acknowledgments
Project Coordinators: Julie Bernas-Pierce, M.Ed. and Namita Jacob
Dr. Creig Hoyt, Nancy Akeson, Gail Calvello, Laila Adle,
Carole Osselaer, Patricia Silva,Laura Davis.
Reviewers: Kay Ferrell, Ph.D., Deborah Hatton, Ph.D., Kathryn Neale Manalo

The Pediatric Visual Diagnosis Fact Sheets are sponsored by a grant from the Blind Children's Center and with support from the Hilton/Perkins Program through a grant from the Conrad Hilton Foundation of Reno, Nevada.

Reproduction For Resale Is Strictly Prohibited (1/98 Bbf)

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August 16, 2001- January 12, 2005

This website is funded in loving memory of Jason S. by his mother Kammy

The information on this site is provided by families, caregivers, and professionals who are or have been caring for a child with Hydranencephaly.

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