Abstract
IT has been found that the results of testing for defective sight by means of test cards may vary according to the degree and standard of illumination of the cards. As the matter is of importance in connexion with certification under the Blind Persons Act, 1920, the Ministry of Health has issued a circular on the subject (Circular 1520. H.M. Stationery Office. Id. net). This suggests that test cards should preferably be illuminated by artificial light, which should be approximately, and not less than, 10 foot-candles, and a simple means is described for effecting this.
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Certification of Blindness. Nature 137, 429 (1936). https://doi.org/10.1038/137429d0
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DOI: https://doi.org/10.1038/137429d0