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Visual Impairment :
Special Educational Needs
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CORRECTING FOCUS DEFECTS

Many people suffer from short or long sight. Most of these are not considered to be visual impairments as they can be fully corrected using glasses. These have been around for centuries. In the 13th century “reading stones” that magnified text developed into spectacles, the earliest recorded being in Pisa in 1286. The illustration showing a scholar holding his glasses is taken from the Nuremburg Chronicle, published in 1493. Since then the science of ophthalmology has developed considerably and the range and type of lenses now available is vast.

Illustration of 15th cenrury scholar with glasses

Illustration of 15th century spectacles

These are a replica of the type of spectacles in use over 500 years ago.

SHORT SIGHT (MYOPIA)

Myopia results from the eye being unable to focus light rays from distant objects onto the retina so the image on the retina is blurred. Light from near objects can be focused so that a clear and sharp image is formed. It can be caused by the distortion of the eye ball or by problems in changing the shape of the lens when focusing.

Diagram showing the correction of short sight

 

LONG SIGHT (HYPERMETROPIA)

Hypermetropia results from the eye being unable to focus light rays from near objects onto the retina so the image on the retina is blurred. Light from distant objects can be focused so that a clear and sharp image is formed.

Diagram showing the correction of long sight