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ELEK LUDVIGH, Ph.D.

Arch Ophthal. 1941;25(3):469-474.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

The use of Snellen test letters is the most common clinical method of determining visual acuity. Nevertheless, the effect that varying the contrast between the letters and the background produces on visual acuity, measured under modern clinical conditions, does not appear to have been investigated heretofore. This problem is of interest from several points of view. It is generally believed that high contrast is essential for the clinical testing of visual acuity. Complaints have been made¹ that the blackness of the letters and the whiteness of the card employed in the Snellen test charts vary from chart to chart and with the age of the chart. Attempts have been made to have test charts constructed in which the figures are maximally black.² Various questions now arise: 1. Is constant and maximal contrast important in the testing of visual acuity? 2. It has been suggested³ that refractive errors . . . [Full Text PDF of this Article]

Author Affiliations
BOSTON

From the Howe Laboratory of Ophthalmology, Harvard University and the Massachusetts Eye and Ear Infirmary.

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