. Railway surgery : a handbook on the management of injuries . ctive vision, the use of the Snellentest types, exhibited in a good light, is advocated (see ). Testing one eye at a time, the various sized typesshould be promptly and perfectly distinguished at the vary-ing distances, by each eye. The cards with radiating lines,or clock-faced, should be used to determine if astigmatismis present, the clearness or blackness of lines of certainangles over others marking the degree and angularity ofdefect. So far, the examination may be conducted in a closedroom, but for range, field, and acut
. Railway surgery : a handbook on the management of injuries . ctive vision, the use of the Snellentest types, exhibited in a good light, is advocated (see ). Testing one eye at a time, the various sized typesshould be promptly and perfectly distinguished at the vary-ing distances, by each eye. The cards with radiating lines,or clock-faced, should be used to determine if astigmatismis present, the clearness or blackness of lines of certainangles over others marking the degree and angularity ofdefect. So far, the examination may be conducted in a closedroom, but for range, field, and acuteness of vision, the in-dividual should face a perspective where various objects,both moving and stationary, may be observed. The ob-jects in the field should be promptly and correctly men-tioned by the observer. In case of inability to reach the normal standard in anyof the tests, the test-glasses should be employed to deter-mine the proper correction to apply. Testing each eyeseparately with the form of lens believed to be able to cor- 250 RAILWAY
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