In preceding publications, 1,2 it was shown that, when a large population of normal eyes was examined by applanation and Schiotz tonometry, the agreement between the value of the arithmetic averages, obtained by the two systems of measurement, was not reflected in measurements obtained in the individual eye. Significant difference in estimates of intraocular pressure of the same eye, obtained by the two methods, was shown to occur with an undesirably high frequency in the clinically important range of intraocular pressure. Further analysis showed that the difference between the two systems was systematic in nature, and could account for significant clinical and experimental error when the two systems are used interchangeably, such as in calculating the coefficient of ocular rigidity, E, and using it to correct the tonographic estimate of outflow facility, C. 2 With the advent of applanation tonometry, which is virtually independent of ocular rigidity, Goldmann 6 proposed
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1959,
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1958,
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