This series of plates is designed to provide a test which gives a quick and accurate assessment of colour vision deficiency of congenital origin. This is the commonest form of colour vision disturbances.
Most cases of congenital colour vision deficiency are characterized by a red-green deficiency which may be of two types: first, a protan type which be absolute (protanapia) or partial (protanomalia), and secondly, a deutan type which may be absolute (deuteranopia) or partial (deuteranomalia).
• In protanopia, the visible range of the spectrum is shorter at the red end and compared with that of the normal, and that part of the spectrum which appears to the normal as blue-green, appears to those with protanopia as grey. • In deuteranopia, that part of the spectrum which appears to the normal as green, appears as grey, and the visible range of the spectrum is divided by this zone into two areas, each of which appears to be of one system of colour.
In the congenital colour vision deficiencies, although very rare, there is total colour blindness which may be typical or atypical. The subject who suffers from typical total blindness shows a complete failure to discriminate any colour variations, usually with an associated impairment of central vision with photophobia and nystagmus.
The use of the charts
The first examination is performed with a circle and a square. Before the examination, it is necessary to make sure that the examinee understands what he is being asked to do. For this purpose the examiner shows the patient plates 1 and 2, tracing the red line, and letting him recognize that they are a circle and a square.
He then says outloud whether it is a circle or a square. In difficult cases, two extra black and white plates may be used to help in unterstanding the instructions. Each of the two plates has a circle and a square rispectilvely, which are exactly the same as plates 1 and 2, and much more esily recognized. Then with plates 3 and 4 the person is tested. He is asked to say what shapes they are.
The second examination is with curved lines. First the examiner shows the examinee that he must trace the curved line. For this plate 5 is used. Then, when the examinee understands what he is to do, he traces plates 6, 7 and 8, step by step. In this case care should be taken to keep the plates at a distance of more than 50 cm or 25 inches if possible.
This series of plates is designed to provide a test which gives a quick and accurate assessment of colour vision deficiency of congenital origin. This is the commonest form of colour vision disturbances.
Most cases of congenital colour vision deficiency are characterized by a red-green deficiency which may be of two types: first, a protan type which be absolute (protanapia) or partial (protanomalia), and secondly, a deutan type which may be absolute (deuteranopia) or partial (deuteranomalia).
• In protanopia, the visible range of the spectrum is shorter at the red end and compared with that of the normal, and that part of the spectrum which appears to the normal as blue-green, appears to those with protanopia as grey. • In deuteranopia, that part of the spectrum which appears to the normal as green, appears as grey, and the visible range of the spectrum is divided by this zone into two areas, each of which appears to be of one system of colour.
In the congenital colour vision deficiencies, although very rare, there is total colour blindness which may be typical or atypical. The subject who suffers from typical total blindness shows a complete failure to discriminate any colour variations, usually with an associated impairment of central vision with photophobia and nystagmus.
The use of the charts
The first examination is performed with a circle and a square. Before the examination, it is necessary to make sure that the examinee understands what he is being asked to do. For this purpose the examiner shows the patient plates 1 and 2, tracing the red line, and letting him recognize that they are a circle and a square.
He then says outloud whether it is a circle or a square. In difficult cases, two extra black and white plates may be used to help in unterstanding the instructions. Each of the two plates has a circle and a square rispectilvely, which are exactly the same as plates 1 and 2, and much more esily recognized. Then with plates 3 and 4 the person is tested. He is asked to say what shapes they are.
The second examination is with curved lines. First the examiner shows the examinee that he must trace the curved line. For this plate 5 is used. Then, when the examinee understands what he is to do, he traces plates 6, 7 and 8, step by step. In this case care should be taken to keep the plates at a distance of more than 50 cm or 25 inches if possible.
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