Phase transitions in ocular tissue — NMR and temperature measurements

Abstract

The human cornea, sclera and lens is studied by nuclear magnetic resonance (NMR) measurements and temperature curves. The bound water fractions of these tissues have been determined as 3% in the cornea, 20% in the sclera and 17% in the lens. In contrast to other investigations we found freezing intervals near -1 degree C.

Determination of the Content of Water in Bovine Corneas by Differential Scanning Calorimetry and Thermogravimetric Analysis

“…There is a severe discrepancy between our value and that obtained by Seiler et al [7] in nuclear magnetic resonance studies o f the cornea which can only partially be explained by sam pling techniques.…”

“…The results obtained by Seiler et al [7] using nuclear mag netic resonance are much lower than our results. Our work using nuclear magnetic res onance imaging suggests that one can only obtain semiquantitative results when estimat ing water using magnetic resonance imaging [ 13].…”

“…In the early stages this was pri marily done by oven drying the tissue at 105-110°C [8,9]. Recent experimental techniques to determine the water in ocular tissues have included calorimetry [10] and nuclear mag netic resonance [7,11,12]. Few attempts have been made to maintain the integrity o f the sample and minimize the errors caused by handling before the analyses.…”

¹Η Magnetic Resonance Imaging Study of Bovine Ocular Tissue

“…At echo times longer than 34 ms, the outer edge of the cor nea is visible. The cornea which has been reported to have from 3 to 32% bound water [7,8] appears to have a relatively high con tent of immobile water.…”

“…NMR has reported the percentages of bound water in ocular tissues to be 3% in the cornea, 20% in the sclera and 17% in the lens [7], DSC of bovine ocular tissues indi cates that the cornea contains 32% and the lens 58% bound water fractions [8].…”