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Scattering Changes (scattering + change)
Selected AbstractsDIEL VARIATIONS IN OPTICAL PROPERTIES OF MICROMONAS PUSILLA (PRASINOPHYCEAE),JOURNAL OF PHYCOLOGY, Issue 6 2002Michele D. DuRand Micromonas pusilla (Butcher) Manton et Parke, a marine prasinophyte, was used to investigate how cell growth and division affect optical properties of phytoplankton over the light:dark cycle. Measurements were made of cell size and concentration, attenuation and absorption coefficients, flow cytometric forward and side light scattering and chl fluorescence, and chl and carbon content. The refractive index was derived from observations and Mie scattering theory. Diel variations occurred, with cells increasing in size, light scattering, and carbon content during daytime photosynthesis and decreasing during nighttime division. Cells averaged 1.6 ,m in diameter and exhibited phased division, with 1.3 divisions per day. Scattering changes resulted primarily from changes in cell size and not refractive index; absorption changes were consistent with a negligible package effect. Measurements over the diel cycle suggest that in M. pusilla carbon-specific attenuation varies with cell size, and this relationship appears to extend to other phytoplankton species. Because M. pusilla is one of the smallest eukaryotic phytoplankton and belongs to a common marine genus, these results will be useful for interpreting in situ light scattering variation. The relationship between forward light scattering (FLS) and volume over the diel cycle for M. pusilla was similar to that determined for a variety of phytoplankton species over a large size range. We propose a method to estimate cellular carbon content directly from FLS, which will improve our estimates of the contribution of different phytoplankton groups to productivity and total carbon content in the oceans. [source] 4245: Non-surgical strategies for PCO preventionACTA OPHTHALMOLOGICA, Issue 2010IM WORMSTONE Purpose Surgical approaches and IOL design have gone some way to reduce the rate of PCO progression. Despite these efforts PCO remains a common and important problem which diminishes the visual quality of patients and is a major financial burden on healthcare providers. If we are to effectively respond to the problem of PCO then a biological solution has to be adopted to reduce/prevent formation of light scattering changes. Methods Methods have been employed to investigate PCO development, which include in vitro cell culture and capsular bag models; in vivo animal models and post-mortem analysis. These have greatly aided our understanding of PCO. Results A number of basic approaches have been identified to prevent PCO. 1) To kill the entire lens epithelial population. This will require a pharmacological agent, therefore delivery of this drug needs to be localised to the target cells, but have limited access to non-target cells; closed capsular bag systems such as perfect capsule provides opportunity to achieve this aim. 2) Maintenance of a cell monolayer on the posterior capsule. In particular the role of TGF, has been investigated, which is known to cause matrix deformation. Disruption of TGF, signalling pathways can suppress matrix deformation and thus reduce light scatter. 3) Recreation of a lens is the ultimate solution. While it has been shown that lens fibre differentiation can be promoted in animal systems, perfect formation of the lens is not achieved and the protein density is typically low relative to the native lens. Conclusion Strategies to prevent PCO are being actively developed, which will are greatly aided by improved drug delivery systems. The development of biological/pharmacological approaches in concert with improved surgical methods and IOL designs should yield benefit to patients. Commercial interest [source] Evaluation of choroidal blood flow after treatment of retinal diseasesACTA OPHTHALMOLOGICA, Issue 2009C CHIQUET Purpose this review aims to summarize studies which assessed the effect of treatment on choroidal blood flow. Methods this presentation will focus on studies using the laser Doppler flowmeter for the analysis of choroidal blood flow parameters (velocity, volume and flow) before and after treatment. Therapies have been assessed in different ocular disease, such as age-related macular degeneration (laser photocoagulation therapy, photodynamic therapy, transpupillary thermotherapy, sildenafil citrate, niacin, pentoxifylline), diabetes mellitus (panretinal photocoagulation, intravenous C-peptide infusion), retinal vein occlusions (isovolemic hemodilution), macular edema (diclofenac), inflammation (corticosteroid), retinal detachment (surgery) or glaucoma (nimodipine, endothelin receptor antagonist, bimatoprost, timolol, trabeculectomy). Results this paper will give insight to the effects of laser treatment (laser photocoagulation, photodynamic therapy), surgery (scleral buckling, trabeculectomy, ocular anesthesia) or systemic drugs on the choroidal blood flow. Methodological considerations will be analyzed, such as the calculation of the sensitivity of the experiments, the comparisons of different groups with or without randomization. Conclusion laser Doppler flowmetry is a useful and a non invasive technique to study the effect of treatment on choroidal blood flow. In ocular disease, investigators should be aware of the tissue scattering changes associated with a retinal or choroidal disease and the necessity of a controlled foveal fixation. [source] Photography of the anterior eye segment according to Scheimpflug's principle: options and limitations , a reviewCLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 1 2009Alfred Wegener PhD Abstract Scheimpflug photography and densitometric image analysis are very precise techniques for light scattering measurement and biometry in the anterior segment of the eye. They provide reproducible data on the characteristics of the anterior eye segment in clinical and experimental studies and the set of data obtained allows discrimination of light scattering changes because of ageing, disease or toxic effects. The techniques can also be used to determine no-effect levels or maximally tolerable dosages of physical and chemical noxious factors. Several Scheimpflug cameras have been marketed, but the only cameras commercially available today are the Nidek EAS 1000 and the Oculus Pentacam. This review outlines the development of the technique and its introduction into ophthalmology. Furthermore, the application of the technique in clinical and experimental ophthalmology as well as in ocular toxicology are presented and discussed. [source] | ||||||||||