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Dominion, Volume 12, Issue 17, 15 October 1918, Page 2

The importance of differentiating between those who are dangerously colour blind—that, unable at all times to distinguish between red and green—and those who are only 1 slightly colour blind is brought out in a recent study conducted by the United States Public Health Service. The following classes are regarded as dangerously colour blind, and therefore to bo excluded from positions in which they would bp required to read coloured signal lights: (1) Those who arc able to see but three or less colours in the spectrum (the normal persons sees six or seven); those who see more than three colours in the spectrum, but who have the red end so shortened as to prevent the re- i cognition of a red light at'a distanco' of two miles; and (3) those with a central scotoma (that is, a blind or partially blind area in the field of vision) for reel and green.Another feature of the investigation' was the study of tho prevalence of colour blindness. Excluding those able to! distinguish five colours in tho spectrum, it was found that colour blindness occurs in about 8.6 per cent.of men and 2.2 per cent, of women. Colour blindness of a degree dangerous in occupations requiring the recognition of coloured signal lights was found to occur in about 3.1 per cent, of men and .'7 per cent, of women. Among refractive conditions of the eye, colour blindness occurs least frequently in eyes apparently without demonstrable refractive error; it occurs most frequently in eyes showing mixed astigmatism. Members and intending members of the Soldiers.' Mothers, Wive?, and Dependants' Leagiu are requested by advertisement to attend a meeting to lo held at the' Esperanto Hall on October 10 at 8 p.m.