PubMed · 8459993
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R Ritch. 1993. An intractable problem.. https://doi.org/10.1016/s0161-6420(93)31655-6
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The concentrations of hyaluronan and galactosaminoglycans -- i.e., chondroitin sulfate and dermatan sulfate -- were measured in the aqueous humor of the eye from patients with exfoliation syndrome and from healthy persons. The glycosaminoglycans/proteoglycans were almost completely precipitated (>97%) with ethanol in the presence of dextran as carrier and, following enzymic digestion, hyaluronan and galactosaminoglycans, were quantitatively converted to delta4,5-disaccharides. Non-degraded heparan sulfate and proteins/glycoproteins were removed by ultrafiltration using a Centricon 3 membrane. Separation and determination of hyaluronan- and galactosaminoglycan-derived delta-disaccharides were performed by ion-suppression HPLC. For an accurate analysis in triplicate, as little as 50 microl of aqueous humor is required. Application of this method to the analysis of samples from six patients with exfoliation syndrome and three healthy persons showed that hyaluronan levels in patients (6.65-16.15 microg ml(-1)) were significantly higher (3-8 times) than in healthy persons (2.0-2.24 microg ml(-1)). There was no significant alteration in the galactosaminoglycan concentration. The obtained data open a new area in the deeper understanding of the exfoliation syndrome pathophysiology and in establishing a highly sensitivity and accurate HPLC method for its diagnosis and patient's follow-up.
We report on quantitative measurements of group refractive indices and group dispersion in water and in human ocular media such as the cornea, the aqueous humor, the lens, artificial intraocular lenses, as well as a total value averaged over the media along the axial eye length of normal subjects and pseudophakic patients in vivo using dual beam partial coherence interferometry. Different optical thickness values due to the dispersion of the cornea are demonstrated using two spectrally displaced light sources. The displacement can be used to indirectly calculate the group dispersion of the human cornea in the spectral region between 810 nm and 860 nm. If the object under investigation is dispersive, resolution is limited due to a broadening of the detected signals. This broadening increases with group dispersion, i.e., the extent to which the group refractive index of the medium varies with wavelength and thickness of the tissue under investigation as well as with the spectral bandwidth of the light source. Measurements of the group dispersion in the cornea, lens and vitreous of pseudophakic and normal human eyes, show that the cornea and the lens are more dispersive than water-by a factor of about 5 and 2, respectively-in the investigated spectral region. The cornea is approximately threefold more dispersive than the human crystalline lens, the aqueous humor is less dispersive than water and the group dispersion of all ocular components together, averaged over the axial length of normal and pseudophakic eyes, was only slightly higher compared to that of water. Since the highly dispersive cornea and lens together have only a thickness of about one sixth of that of the axial eye length, it seems that their contribution to the group dispersive effect along the whole axial eye length is only small.
The hypothesis is advanced that the purpose of the eyeball movements during REM sleep is to stir the aqueous humor behind the closed lids and so avoid the risk that its stagnation could cause corneal anoxia. The relevance of the hypothesis to evolutionary biology and intensive care nursing is discussed.