Industrial visual screening. Advantages and disadvantages of various instruments

The ideal test for visual screening is one which is easily performed by a technician with limited training, inexpensive and not time-consuming, easily understandable by all applicants, and one which will correspond generally with a more thorough examination by an ophthalmologist. The ideal screening technique should test accurately those functions needed for any particular occupation. The visual screeners now in great preponderance have certain advantages for ease and are generally acceptable for approximating the visual acuity. Visual screeners do not accurately test the astigmatic applicant, and they have not proven their value in testing depth perception and color vision. The use of the Harrington Flocks Screener is recommended for testing the visual field. The use of the Verhoeff Steropter for depth perception and the American Optical pseudoisochromatic plates for color testing is recommended when these tests are needed. The old Snellen test cards, or the projector chart for measuring distance vision, and the test cards for measuring near vision are often much more reliable than are the visual screeners.