VISUALLY IMPAIRED CHILDREN: How do I know if my child has a cortical visual impairment? Part One

Wednesday 30 November 2011

How do I know if my child has a cortical visual impairment? Part One

CVI is not easy to diagnose and it may not even be diagnosed initially in the hospital. Nevertheless it is now as widespread a problem as visual impairment is amongst babies and children. What is often confusing to people is that if the child’s eyes are normal how is it the child cannot see? Why does the child not smile back for instance?

How can you tell whether a child is visually impaired, cognitively delayed, or if there is something else that is not so easily diagnosable: cerebral or cortical visually impairment? Often a brain scan (MRI) may help to pinpoint areas of damage in the cortex.

The region called the parietal lobes is the attention command centre of the brain. This is the area that controls a person’s ability to pay selective attention. Damaged brain cells in this area can be why children have difficulty with attention and are easily distracted. If there is damage in the flow of information from the occipital lobes to the parietal lobes ( an area called the ‘dorsal stream’ ) it can have a significant effect on the child’s ability to isolate and make sense of sensory information, move about and use their vision to guide movements.

The visually evoked potential assessment refers to the measurement of a visual signal from the eyes to the brain. Flashing black and white squares appear on a monitor and the child’s response recorded.

Observation of the child’s visual behaviour is important and a history taking with the parents is another essential aspect of the diagnosis.

CVI is different from ocular visual impairment. Visual impairment is an eye globe issue. It concerns something malfunctioning within the eye itself or the optic nerve leading from the eye to the brain. CVI is an impairment of vision that is caused by damage to the brain tissues. Much of the brain is concerned with some aspect of seeing. Whereas a visual impairment can be measured fairly accurately, CVI is less easy to quantify precisely. It is also quite difficult to manage compared with a ‘malfunction’ of the eye mechanism. An optical aid can give a short sighted person good vision but there is no gadget or device that fixes CVI.

A common cause is lack of oxygen to the brain or hypoxia, which can happen during birth or at any point during gestation. The result of poor blood supply to the brain and resultant lack of oxygen is that cells in the brain die. CVI is commonly associated with certain other conditions such as cerebral palsy, microcephalus or epilepsy. Wherever there is brain damage it is possible that some visual difficulties may ensue by the very nature of the functioning of the brain.

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One of the great inspirations to me must be Helen Keller. Helen Keller was not born blind and deaf; it was not until she was 19 months old that she contracted an illness described by doctors as "an acute congestion of the stomach and the brain", which might have been scarlet fever or meningitis. The illness left her deaf and blind. At that time, she was able to communicate somewhat with Martha Washington, the six-year-old daughter of the family cook, who understood her signs; by the age of seven, she had over 60 home signs to communicate with her family.

In 1886, her mother, inspired by an account in Charles Dickens' American Notes of the successful education of another deaf and blind woman, Laura Bridgman, dispatched young Helen, accompanied by her father, to seek out Dr. J. Julian Chisolm, an eye, ear, nose, and throat specialist in Baltimore, for advice.^[11] He subsequently put them in touch with Alexander Graham Bell, who was working with deaf children at the time. Bell advised the couple to contact the Perkins Institute for the Blind, the school where Bridgman had been educated, which was then located in South Boston. Michael Anaganos, the school's director, asked former student Anne Sullivan, herself visually impaired and only 20 years old, to become Keller's instructor. It was the beginning of a 49-year-long relationship, Sullivan evolving into governess and then eventual companion.

Anne Sullivan arrived at Keller's house in March 1887, and immediately began to teach Helen to communicate by spelling words into her hand, beginning with "d-o-l-l" for the doll that she had brought Keller as a present. Keller was frustrated, at first, because she did not understand that every object had a word uniquely identifying it. In fact, when Sullivan was trying to teach Keller the word for "mug", Keller became so frustrated she broke the doll.

Keller's big breakthrough in communication came the next month, when she realized that the motions her teacher was making on the palm of her hand, while running cool water over her other hand, symbolized the idea of "water"; she then nearly exhausted Sullivan demanding the names of all the other familiar objects in her world.

Due to a protruding left eye, Keller was usually photographed in profile. Both her eyes were replaced in adulthood with glass replicas for "medical and cosmetic reasons". Wikipedia

Ophthalmology and opthalmologists

Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems. The ophthalmologist is the eye doctor. Since ophthalmologists perform operations on eyes, they are considered to be both surgical and medical specialists.

The word ophthalmology comes from the Greek roots ophthalmos meaning eye and logos meaning word, thought, or discourse; ophthalmology literally means "the science of eyes". As a discipline, it applies to animal eyes also, since the differences from human practice are surprisingly minor and are related mainly to differences in anatomy or prevalence, not differences in disease processes. However, veterinary medicine is regulated separately in many countries and states/provinces resulting in few ophthalmologists treating both humans and animals.

History of Ophthalmology

Seventeenth and eighteenth centuries

The seventeenth and eighteenth century saw the use of hand lenses (by Malpighi), microscopes (van Leeuwenhoek), preparations for fixing the eye for study (Ruysch) and later the freezing of the eye (Petit). This allowed for detailed study of the eye and an advanced model. Some mistakes persisted such as: why the pupil changed size (seen to be vessels of the iris filling with blood), the existence of the posterior chamber, and of course the nature of the retina. In 1722 Leeuwenhoek noted the existence of rods and cones^,though they were not properly discovered until Gottfried Reinhold Treviranus in 1834 by use of a microscope.

Ophthalmic surgery in Great Britain

The first ophthalmic surgeon in Great Britain was John Freke, appointed to the position by the Governors of St Bartholomew's Hospital in 1727, but the establishment of the first dedicated ophthalmic hospital in 1805; now called Moorfields Eye Hospital in London, England was a transforming event in modern ophthalmology. Clinical developments at Moorfields and the founding of the Institute of Ophthalmology (now part of the University College London) by Sir Stewart Duke Elder established the site as the largest eye hospital in the world and a nexus for ophthalmic research.

Ophthalmology and ophthalmologists

Purkinje is a known to all ophthalmologists for Purkinje's cells, Purkinje's images. Jan Evangelista Purkinje was a versatile scholar with wide-ranging interests and an exceptional capacity for innovative thinking. He used the name “Purkinje” until 1850, from whence he used the correct spelling, Pyrkyně. We use Purkinje for the eponyms because that is the more common. Purkinje was a Czech nationalist and had a major influence on Czech cultural life in the middle of the 19th century. He was a friend of the famous German poet Johann Wolfgang von Goethe, who wrote about Purkinje: “and should you fail to understand, let Purkyně give you a hand!” Purkinje published a Czech translation of Friedrich Schiller's poems, and translated works of William Shakespeare into Czech.

Purkinje created the world’s first department of physiology at the University of Breslau, Prussia in 1839 and the first official physiological laboratory, known as the Physiological Institute, in 1842. Purkinje used to believe that that experiments in one's own body ("in corpore nobili") gave more practical results than those in animal experiment ("in corpore vili") or in fatally ill patients. And when he was a medical student, Purkinje used to investigate the physiology of sight by experimenting on himself with a variety of drugs, including Belladonna. His interest in the physiology of light led him to make animated cartoons, and thus he became one of the earliest motion picture pioneers.

He is best known for his discovery of Purkinje cells, large nerve cells with many branching extensions found in the cortex of the cerebral cortex. He is also known for his discovery of Purkinje fibers, the fibrous tissue that conducts the pacemaker stimulus along the inside walls of the ventricles to all parts of the heart. It was Purkinje, who introduced the scientific terms plasma. An early user of the improved compound microscope, he discovered the sweat glands of the skin, germinal vesicles. He recognized fingerprints as a means of identification and noted the protein-digesting power of pancreatic extracts. He died on July 25 of 1868.


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Wednesday 30 November 2011

How do I know if my child has a cortical visual impairment? Part One

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