PURPOSE: Pharmacologic vitreolysis is a new approach to improve vitreo-retinal surgery. Ultimately, the development of drugs to liquefy and detach vitreous from retina should prevent disease by mitigating the contribution of vitreous to retinopathy and eliminate the need for surgery. However, the mechanism of action of pharmacologic vitreolysis remains unclear. The technique of Dynamic light scattering (DLS) was used to evaluate the effects of microplasmin by following the diffusion coefficients of spherical polystyrene nano-particles injected with microplasmin into the vitreous. METHODS: Diffusion coefficients in dissected (n=9) porcine eyes were measured in vitro. DLS was performed on all specimens at 37°C as often as every 10 minutes for up to 6 hours following injections of human recombinant microplasmin at doses ranging from 0.125 mg to 0.8 mg, with 20 nm diameter tracer nanospheres. RESULTS: DLS findings in untreated porcine vitreous were similar to the previously described findings in bovine and human vitreous, demonstrating a fast (early) component, resulting from the flexible hyaluronan molecules, and a slow (late) component, resulting form the stiff collagen molecules. Microplasmin increased porcine vitreous diffusion coefficients. A new approach was developed to use DLS measurements of vitreous diffusion coefficients to evaluate the effects of microplasmin in intact eyes. CONCLUSIONS: Pharmacologic vitreolysis with human recombinant microplasmin increases vitreous diffusion coefficients in vitro. The results of these studies indicate that this new approach using DLS to measure vitreous diffusion coefficients can be used to study the effects of pharmacologic vitreolysis using microplasmin and other agents in intact eyes and ultimately in vivo.
The non-invasive optical technique of dynamic light scattering (DLS) is routinely used to characterize dilute and transparent sub-micron particle dispersions in laboratory environments. A variety of industrial and biological applications would however greatly benefit from on-line monitoring of dispersions under flowing conditions. In this paper we present a model experiment to study flowing dispersions of polystyrene latex particles of varying sizes under varying flow conditions using a newly developed fiber optic DLS probe. A modified correlation function proposed in an earlier study by Chowdhury et al. is applied to the analysis of extracting size and velocity of laminar flowing particulate dispersions. The complimentary technique of laser Doppler velocimetry is also used to measure the speed of moving particles to confirm the DLS findings.
In this paper we present preliminary measurements on the effects of zero gravity environment on the choroidal blood flow on human volunteer subjects. These experiments were conducted, for the first time, on-board a wide body aircraft (KC-135) during parabolic flight trajectories (0g to 2g environment) using a head-mounted miniature laser Doppler flowmeter.
Dynamic light scattering (DLS) particle size measurments are reported for turbid systems. These include particulate dispersions and suspensions of macromolecules in a wide (7 nm - 800 nm) particle size (diameter) range which look as transparent as water and as turbid as milk (turbidity approximately 6 - 7 orders of magnitude higher than water) and samples of lenticular and skin tissues. Our results indicate a significant improvement in achieving non-invasive, compact, robust, and remotely operated DLS probes which are able to push the envelope of DLS utilization to extremely turbid samples of a variety of particle type and size of macromolecules which were hitherto not possible.
A compact fiber optic probe developed by Ansari et al. for fluids experiments in the challenging conditions of a microgravity environment on-board a space shuttle orbiter has been applied to obtain `cataractograms' in transgenic mice to study early onset of cataractogenesis. Cataractograms are topographical contour maps of the lens which are obtained non-invasively by scanning the eye with the probe in three-dimensions (x, y, and z directions). This new method provides a visual means, in false color, for quantitative detection and monitoring of cataracts in the entire lens. The portion of lens mapped is only limited by the degree of pupil dilation. The dilated pupil is about 1 mm for the transgenic mice system reported in this study.
A newly developed backscattering fiber optic probe using the technique of dynamic light scattering (DLS) has been applied to obtain three-dimensional structural information in excised, but intact bovine lens and vitreous humor.
The ability of reliable, non-invasive, and quantitative characterization of biological fluids containing submicroscopic particles in a in-situ/in-vivo environment may open new possibilities to better understand these fluids. This paper focuses the use of a newly developed dynamic light scattering fiber optic probe to assist in this goal. A in-situ/on-line application to study protein aggregation and growth of protein crystals from solutions and one in-vivo application involving study of cataractogenesis in an animal model are presented.
A new fiber optic probe is developed to study different parts of the eye. The probe positioned in front of an eye, delivers a low power light from a laser diode into the eye and guides the light which is back scattered by different components (aqueous humor, lens, and vitreous humor) of the eye through a receiving optical fiber to a photo detector. The probe provides rapid determination of macromolecular diffusivities and their respective size distributions in the eye lens and the gel-like material in the vitreous humor. We report alpha-crystalline size distributions, as a function of penetration depth, inside the lens and hyaluronic acid molecular size distribution in the vitreous body. In a clinical setting, the probe can be mounted on a slit- lamp apparatus simply by using a H-ruby lens holder. The capability of detecting cataracts, both nuclear and peripheral, in their early stages of formation, in a non invasive and quantitative fashion, has the potential in patient monitoring and in developing and testing new drugs or diet therapies to 'dissolve' or slow down the cataract formation before surgery is necessary. The ability to detect biochemical and macromolecular changes in the vitreous structure can be very useful in identifying certain diseases of the posterior chamber, e.g., posterior vitreous detachment.
We report non-invasive particle size measurements of polystyrene latex colloidal particles and bovine serum albumin (BSA) protein molecules suspended in tiny hanging fluid drops of 30 (mu) L volume using a newly designed fiber optic probe. The probe is based upon the principles of the technique of dynamic light scattering (DLS). The motivation for this work comes from growing protein crystals in outer space. Protein crystals have been grown previously in hanging drops in microgravity experiments on-board the space shuttle orbiter. However, obtaining quantitative information on nucleation and growth of the protein crystals in real time has always been a desired goal, but hitherto not achieved. Several protein researchers have shown interest in using DLS to monitor crystal growth process in a droplet, but elaborate instrumentation and optical alignment problems have made in-situ applications difficult. We demonstrate that such an experiment is now possible. Our system offers fast (5 seconds) determination of particle size, utilizes safe levels of very low laser power (less than or equal to 0.2 mW), a small scattering volume (approximately 2 multiplied by 10-5 mm3) and high spatial coherence (beta) values. This is a major step forward when compared to currently available DLS systems.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.