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R. C. Augusteyn; Human Lens Internal Structure: Relationship Between in vivo and in vitro Observations. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2345.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the relationship between in vivo and in vitro observations on lens growth and internal structure.
Data on lens dimensions, weights, properties, gradients and internal structures were obtained from the literature and from measurements in the author’s laboratory. Dry weight distributions were calculated from refractive index gradients.
Slit lamp biomicroscopy reveals several zones of optical discontinuity, labeled the embryonic, foetal, juvenile and adult nuclei and the cortex. Lyophilization, hydrodissection and manual peeling of cell layers, as well as the location of a diffusion barrier and the development of the RI gradient, indicate that the lens contains a distinct nuclear core measuring ~7 x 3mm and a growing cortex. Comparison of the calculated dry weight contents of the various in vivo nuclear zones with the measured dry weights of in vitro lenses and that of the nuclear core reveals that the combined in vivo nuclear zones correspond to the in vitro nuclear core. This is consistent with the observation that the protein distribution is identical in all nuclear layers but different from that in the cortex. The dry weights also indicate that the embryonic, foetal and juvenile nuclei as well as most of the adult nucleus were produced during prenatal life. The remaining cells comprising the adult nucleus were completely laid down by 3 months after birth, following which lens growth takes place in the cortex only.
Contrary to the implications in the nomenclature assigned to the lens zones of discontinuity, the tissues comprising the adult, juvenile, foetal and embryonic nuclei are all generated during the prenatal growth mode which ends around 3 months postnatally. All further lens growth is restricted to the cortex. It is suggested that the use of the nuclear descriptions be abandoned.
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