The Total Osmotic Pressure of Tears in Normal and Various Pathologic Conditions

Abstract

The concept of the hypertonicity of tears originated with Massart¹ in 1889. By instilling various solutions of different osmotic pressure into the eye, he determined by subjective responses that the concentration of a solution which produces the least discomfort corresponded to a 1.4 per cent solution of NaCl. Massart's results were accepted readily and were included in the major pharmacopeias and textbooks. In 1930 Ridley^2,3 measured the osmotic pressure of tears of 3 persons by the depression of the freezing point and found the osmotic pressure of tears to be slightly below that of human blood. Krogh⁴ used a modification of the Baldes⁵ vapor-pressure method for the determination of osmotic pressure. Krogh, Lund, and Pedersen-Bjergaard⁶ found the osmotic pressures of 10 samples of tears equal to those in solutions of from 0.87 to 0.92 per cent NaCl. Schaeffer,⁷ using a capillary-tube method, estimated the