This is a discussion on CVI - Cortical Visual Impairment within the Parenting Special Needs Child forum, part of the MummySG Special Group category; Cortical Visual Impairment or sometimes referred to as Cerebral Visual Impairment is the highest cause of visual impairment among children ...
Cortical Visual Impairment or sometimes referred to as Cerebral Visual Impairment is the highest cause of visual impairment among children with multiple disabilities. However, because of the more obvious (easily noticed) physical impairments, CVI is usually overlooked or not considered an important area for intervention. On top of that, there are few doctors and ophthalmologists who are able to accurately diagnose CVI. Some of them have never even heard of the term, and brushes it off as one of those "alternative diagnosis".
CVI is a true visual impairment, that occurs due to injury, insults or some malformations in the brain and its functions. Hence, many children with CP, seizures, etc. could possibly have an undiagnosed CVI. Because vision affects the development in all the other areas - physical, communication, social, cognitive, etc, children with GDD could also have undiagnosed CVI.
Recently, a presentation was made to EIPIC centres in Singapore, calling for teacher screening of visual disorders in multiply disabled children. I hope there will be greater follow-up by the centres and their teachers.
In many cases of CVI, vision does actually improve with proper intervention, especially in the first years of the child's life. Vision is a learned process, and infants can be taught to 'see', especially those with CVI.
I would like to share the article from the American Printing House for the Blind, their article on CVI below:
What is CVI?
Why your child/students may have impaired vision:
Ocular disorders: pathology of the eye(s)
Neurological visual disorders: disturbed or reduced vision due to various brain abnormalities.
The two types of visual disorders (ocular & neurological) can coexist.
Cortical visual impairment (CVI) is a neurological visual disorder. It is the fastest growing visual impairment diagnosis today.
Definition for Medical Purposes:
Cortical visual impairment (CVI) may be defined as bilaterally diminished visual acuity caused by damage to the occipital lobes and or to the geniculostriate visual pathway. CVI is almost invariably associated with an inefficient, disturbed visual sense because of the widespread brain disturbance. See brain diagrams.
Definition for Educational Purposes:
Cortical visual impairment (CVI) is a neurological disorder, which results in unique visual responses to people, educational materials, and to the environment. When students with these visual/behavioral characteristics are shown to have loss of acuity or judged by their performance to be visually impaired, they are considered to have CVI.
Note: A student whose visual functioning is reduced by a brain injury or dysfunction may be considered blind for educational purposes if visual function is equal to or less than the legal definition of ocular blindness. See Federal Quota.
Visual impairment was defined in the past by loss of acuity (how far we see) and also by the severity of visual field loss (blind area). This definition was originally designed for characterizing visually impaired adults who required social assistance and not for children with visual impairment caused by various eye conditions. Even though it did not accurately represent visual abilities, the definition was widely accepted, but it adversely influenced our thinking about visual impairment. Services were developed worldwide for only those people with visual problems fitting this definition while others with obvious visual difficulties who required intervention were excluded.
During the last several decades, our understanding of vision has markedly improved. It is now realized that vision is not a single sense but a combination of complex senses which have evolved over millions of years. Almost the entire brain is involved in the process of seeing. In different locations there are specialized areas for distance vision, recognition of faces, objects, colors, contrast, and movement. There are also areas of the brain that coordinate visually-directed movements, and process visual information to achieve perceptions of directionality and depth. CVI is caused by widespread damage to the brain, which affects most of the specialized visual centers, resulting in a damaged, inefficient visual sense. When only a small visual area is affected, it can result in a specific visual disorder, but not in CVI.
Because in the past everyone who was considered to be visually impaired had to have reduced or absent visual acuity, the medical definition of CVI also emphasized loss of ability to see in the distance (reduced acuity). It was hoped that once the correct diagnosis was made, children with CVI would be appropriately managed by a variety of professionals, including educators.
The medical definition of CVI is not well understood by non-medical professionals. While acuity testing is difficult in the young and disabled for physicians, it is even more difficult for teachers. Also, there are many children with visual problems similar to CVI, except they have normal acuity. This visual condition is called "cortical visual dysfunction" (CVD). The educational management of children with CVI and CVD is similar. It is now known that with time the visual acuity of children with CVI tends to improve. Therefore the diagnosis of CVI could change to CVD over time. Both groups require remedial education, which necessitates an increased number of specialized teachers. Based on the above discussion, it is clear that there is a need for an educational definition of CVI and CVD, which addresses the needs of these children.
CVI is suspected by:
a normal or close to normal eye examination;
a medical history which includes neurological problems; and
the presence of unique visual/behavioral characteristics.
Four major causes of CVI:
Unique visual/behavioral characteristics of CVI:
Normal or minimally abnormal eye exam (CVI may co-exist with optic nerve atrophy, hypoplasia or dysplasia and ROP.)
Difficulty with visual novelty (The individual prefers to look at old objects, not new, and lacks visual curiosity.)
Visually attends in near space only
Difficulties with visual complexity/crowding (Individual performs best when one sensory input is presented at a time, when the surrounding environment lacks clutter, and the object being presented is simple.)
Non-purposeful gaze/light gazing behaviors
Distinct color preference (Preferences are predominantly red and yellow, but could be any color.)
Visual field deficits (It is not so much the severity of the field loss, but where the field loss is located.)
Visual latency (The individual's visual responses are slow, often delayed.)
Attraction to movement, especially rapid movements.
Absent or atypical visual reflexive responses (The individual fails to blink at threatening motions.)
Atypical visual motor behaviors (Look and touch occur as separate functions, e.g., child looks, turns head away from item, then reaches for it.)
Inefficient, highly variable visual sense
Other Neurological Vision Disorders
Cortical And Cerebral Blindness
Both of these terms are often used to describe CVI. Blindness to most people means total absence of vision, and individuals with CVI are rarely, if ever, totally blind, the word "blindness" tends to be replaced with "visual impairment." People living in the United States, Canada, Mexico, and many other countries prefer to use "cortical" visual impairment for CVI, while some European countries refer to it as "cerebral" visual impairment. OCCIPITAL BLINDNESS should not be used to describe CVI. The term suggests that the occipital lobes are the brain centers for vision but it is the entire brain which "sees." The understanding of CVI is still evolving, which is one of the reasons for some of the inappropriate terms used today. (One of the aims of this project is to eliminate inappropriate terms.)
Neurological visual impairment(s)
This term is often used to indicate that the visual disorder(s) is(are) caused by brain rather than eye abnormalities. CVI is one of the neurological visual conditions because it is caused by brain abnormalities. There are many different neurological visual disorders in addition to CVI such as visual agnosia, visual neglect, lack of face recognition, homonymous hemianopia, poor depth perception, various visual perceptual disorders, among others.
Homonymous hemianopia or hemianopsia
These are medical terms which imply that a visual field defect (blind area) affects the same half of each eye, either on the right or left side. These blind areas are caused by brain lesions which are on the opposite side from the visual field defect. Double, homonymous hemianopia would imply that the visual field defects involve both halves of each eye. Individuals with CVI very frequently have visual field loss, but in addition, their remaining visual sense is severely disturbed. Therefore homonymous hemianopia is not the same as CVI.
This term implies that there is a non-seeing, blind area within the visual field which may occur due to damage of the visual pathways, or to the retina. Scotomas can be large or small. Individuals who only have scotomas should have no difficulties interpreting visual messages outside the visual field loss, therefore this term should not be confused with CVI.
Delayed Visual Maturation/Delayed Visual Development
Children are not born with a fully developed visual sense but acquire their visual skills gradually. Delayed visual maturation is diagnosed when young infants exhibit markedly delayed visual function, due to various causes. Delayed visual development is a more appropriate term because while the delayed visual function in most instances improves, with appropriate management and with time; it only rarely becomes entirely normal.
Occasionally individuals claim to have disturbed, decreased, or even absent vision without corroborating evidence of abnormality found on examination and detailed visual testing. These complaints need to be taken seriously because they may be due to underlying psychological problems which require treatment. Functional visual disorders can have many different causes and some individuals may even fake their disturbed vision for various reasons. Functional blindness should not be confused with CVI because it is an entirely different visual condition.
This term is used to identify the inability to recognize common objects because of specific brain problems, regardless of visual acuity.
This is characterized by the inability or impaired perception of visual information, usually on one side of the body, due to disturbances with attention mechanisms in the presence of normal acuity.
Hope more people will be better aware of the presence of CVI among children with multiple or complex disabilities.