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Visual Impairment :
Special Educational Needs
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UNDERSTANDING VISUAL IMPAIRMENT 

Pupils who are severely visually impaired fall into three categories, each with differing needs. Most have some residual functional vision, but are classified as being blind. Their level of functional vision is extremely limited, and many have fluctuations in level of vision in different conditions. Some have suffered a deterioration in their vision and have no remaining functional vision, but do have a visual memory. A small minority are congenitally totally blind and have had no functional vision from birth, so have no concept of what vision is, and therefore have no concept of colour, shape of objects or any spatial awareness.

To understand visual impairment we need to understand how the eyes work, how information is transmitted to the brain and how the brain interprets the information it receives. The processes involved are detection, transmission and interpretation.

 
Here’s a short set of human biology lessons !

 

The Human body is very complex. It made up of billions of cells of different types (probably between 50 and 100 million million cells in an adult), which form tissues and organs to create ten different systems that allow the body to function. Some vital organs, such as the brain, heart and lungs, are protected by the skeleton and all have some protection within the torso.


The diagram shows the levels of org
anisation of the body.

Diagram showing the levels of organisation within the human body

The systems are Respiration, Circulation, Digestion, Excretion, Endocrine, Nervous, Support, Movement, Reproductive and the Skin. The shape of the body is maintained by 630 muscles attached to the skeleton of 206 bones.

The sensory part of the nervous system detects what is happening in and around the body. Different sensors detect sound, light, smell and taste, movement, temperature change, the position of the body, touch, pressure and pain. Nerve impulses from the sensory cells and organs are transmitted to the brain which interprets the information received and determines the response. The motor part of the nervous system controls the movement of muscles. The nerve cells, called neurones, are long cells which allow minute electrical impulses to travel along them. There is a minute gap between successive neurones called a synapse. When a nerve impulse reaches a synapse the nerve releases a chemical neurotransmitter (acetylcholine) which travels across the gap stimulating an impulse in the next neurone. Nerve impulses travel at high speed through the body so the time taken to detect a stimulus and respond is very fast, a fraction of a second).

The central nervous system (CNS) comprises of the spinal column and the brain. These are very delicate organs which are easily damaged so the spinal column is encases in the vertebrae in the spine and the brain is encased within the skull and surrounded by fluid. Damage to any nervous tissue is irreparable.