DETERMINATION OF THE VELOCITY OF ULTRASOUND IN THE HUMAN LENS AND VITREOUS

Determinations of the velocity of ultrasoundl) in various biological tissues have been reported by several authors. Thus, Ludwig (1950) found the velocity to be 1515 m/sec in the brain of the dog, 1506 d s e c in the brain of the pig, and 1515, 1553 and 1557 m/sec, respectively, in the spleen, liver and kidney of the pig (temperature varying between +24O and f25' C). He also measured the velocity in human muscular tissue at + 3 7 O C, using a frequency of 1.25 and 2.5 Mhz, and found a range of 1490 to 1610 mhec (mean 1540 d s e c ) . Oksala E;: Lehtinen (1958) made similar determinations of the velocity in some ocular tissues. Since no human material was available, the measurements were carried out in eyes from newly-slaughtered cattle. The experimental temperature was +22OC, and the frequency 4 Mhz; the error of the method was k 0.5 "/o. Their results are listed in table I. Yamamoto et al. (1961) also determined the velocity in various tissues of animal eyes (see table I). They used the same frequency of ultrasound as Oksala & Lehtinen, but did not state the temperature. In the same paper, the velocity in human lenses with cataract is given as 1570 m/sec; here as well, the temperature is not mentioned. A definite correlation is known to exist between the velocity of ultrasound and temperature. Consequently, it is of paramount importance, when making intraocular measurements of distance in vivo by means of ultrasound, to be acquainted with the velocity in different tissues at $37' C. Such a correlation has, in fact. been shown to be present in ocular tissues (Jansson & Sundmark 1961). Detei-minations were made in the lens and vitreous of newly-slaughtered