An apparatus was designed, based on the principle of Grayson´s internal calorimetry, for the determination of the choroidal blood flow with thermistor as a sensing element. Experiments with water; 10%, 20%, 30%, and 50.% gelatin solution; living and dead rabbit eye and enucleated human eye showed that there was a linear relationship between the thermal conductivities and the currents required to raise the heating thermistor by 1°C. Thus it was found that the Carslaw´s law could, be applied in these experiments.
In rabbit´s eyes, thermistors were introduced into the suprachoroidal space after separating the sclera from the underlying choroid. At the same-time, one of the vortex veins was cut right after the vein emerge from the sclera, and the amount of blood was absorbed and weighed. The results showed that when the blood flow was in the lower range, the thermal conductivity increased abruptly. When the blood flow increased, the increase in the thermal conductivity was at a more slower rate. In the physiological range of blood flow, however, there was a linear relationship between the blood flow and the changes in the thermal conductivity.
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