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V. Choh, X. Su, C. Vesco, J. Fleming; Densities of Bovine Ocular Components. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5564.
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© ARVO (1962-2015); The Authors (2016-present)
Mass density is an important parameter for ultrasound applications. Properties such as attenuation, reflectivity and absorption of acoustic signals are related to tissue density. While many studies have measured the densities of ocular components, they have often been limited to one or two ocular components. As a consequence, compilations of density data contain gaps in data. No study has compared the densities of all the ocular components in the same species. This study was undertaken to determine the densities of all components of the bovine eye.
Eyes were obtained from a local abattoir the day of the experiment. For liquid ocular components (aqueous and vitreous humours), densities were calculated (n=11) from each measured volume and mass. Solid ocular components (cornea, lens, retina, choroid, sclera) were measured in two ways. In the first, a densimeter kit was used to measure wet and dry weights of the ocular tissues before calculating the density (n=10). The second method used observations of the buoyancy state of the tissues in various concentrations of sucrose (Archimedes Principle; n=11). If a tissue was less dense than the solution, it floated; if more dense, it sank. If the densities were similar, the tissue was suspended at the level in which it was placed into the solution. Sucrose solutions were calibrated prior to the experiment to determine their densities.
The two density measurement methods provided similar mean densities, but yielded a different relative order. Using the densimeter, the relative order of density, from least to most, was: retina (mean ± sd: 1.034 ± 0.007 g/cm3), cornea (1.058 ± 0.007 g/cm3), choroid (1.063 ± 0.016 g/cm3), sclera (1.077 ± 0.005 g/cm3) and lens (1.098 ± 0.019 g/cm3). The density ranges of some of the tissues overlapped with each other. The corneal and choroidal densities were similar (p=0.2567), while all other tissue densities were distinct (p<0.0006; all comparisons). In contrast, densities of the tissues collected using the sucrose method did not overlap, and all were distinct from each other (p<0.0001; all comparisons). The relative order was: retina (1.033 ± 0.002 g/cm3), choroid (1.052 ± 0.002 g/cm3), cornea (1.061 ± 0.004 g/cm3), sclera (1.076 ± 0.003 g/cm3) and lens (1.104 ± 0.001 g/cm3). Aqueous and vitreous humours averaged to 1.007 ± 0.010 g/cm3 and 1.005 ± 0.012 g/cm3, respectively.
The results indicate a general concurrence between the two different methods in terms of absolute density. The difference in the relative order of the choroidal density is likely due to the combination of an imprecision of the densimeter and a natural proximity of the corneal and choroidal densities.
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