Michael A. DellaVecchia

Coherent fiber optic sensor for early detection of cataractogenesis in a human eye lens

A lensless backscatter fiber optic probe is used to measure the size distribution of protein molecules inside an excised, but intact, human eye lens. The fiber optic probe, about 5 mm in diameter, can be positioned arbitrarily close to the anterior surface of the eye; it is a transreceiver, which delivers a Gaussian laser beam into a small region inside the lens and provides a coherent detection of the laser light scattered by the protein molecules in the backward direction. Protein sizes determined from the fast and slow diffusion coefficients show good correlation with the age of the lens and cataractogenesis.

Refractive index matching of tissue components as a new technology for correlation and diffusing-photon spectroscopy and imaging

The refractive index matching of components of highly scattering tissue has a strong influence on its transmittance and reflectance what can be considered as a new tool for imaging within relatively thick tissues. We present experimental data on various solutions, gels and oils influence on optical properties of in vivo human eye and in vivo human skin. The dynamics of tissue optical properties depending on matter diffusion rate within tissue is studied. The possible application of refractive index matching effect for diffusing-photon imaging is discussed.

Fiber optic sensor for ophthalmic refractive diagnostics

This paper demonstrates the application of a lensless fiber optic spectrometer (sensor) to study the onset of cataracts. This new miniaturized and rugged fiber optic probe is based upon dynamic light scattering (DLS) principles. It has no moving parts, no apertures, and requires no optical alignment. It is flexible and easy to use. Results are presented for cold-induced cataract in excised bovine eye lenses, and aging effects in excised human eye lenses. The device can be easily incorporated into a slit-lamp apparatus (ophthalmoscope) for complete eye diagnostics.

Fiber optic system for in-vivo sizing of proteins in animal eye lenses

A compact fiber optic system, utilizing a lensless backscatter fiber optic probe, and a semiconductor laser is used as a non-invasive tool for in vivo characterization of the proteins in the eye lens of several animals. The system exploits the extremely sensitive technique of dynamic light scattering, which uses a laser beam to probe the temporal characteristics of the proteins present in eye lens fluid. The technique, with appropriate electronics and signal processing provides a rapid means of determining the size of the (alpha) -crystallin in the protein-water system. Changes in the size of the protein molecules can be tracked over the age of the eye lens; an abrupt increase in size is associated with the early cataractous formation. This paper describes the fiber optic system and discusses results obtained from measurements made on sedated rabbits, pigs and cats. A clear difference in the size of the (alpha) -crystallin of normal and cataractous lenses is observed.

Dynamic light scattering in veterinary medicine: refinement of diagnostic criteria

In dynamic light scattering (DLS), the structure or material of interest, suspended in a fluid, is illuminated by a beam of laser light and the scattered light is interpreted in terms of diffusion coefficient, particle size or its distribution. DLS has shown clear promise as a non-invasive, objective and precise diagnostic modality for investigation of lens opacity (cataract) and other medical and toxicological problems. The clinical potential of LDS has been demonstrated in several species both in vivo and in vitro. In many clinical cases, discernment between normal and diseased patients is possible by simple inspection of the particle size distribution. However a more rigorous and sensitive classification scheme is needed, particularly for evaluation of therapy and estimation of tissue injury. The data supplied by DLS investigation is inherently multivariate and its most efficient interpretation requires a multivariate approach which includes the variability among specimens as well as any correlation among the variables (e.g. across the particle size distribution). We present a brief review of DLS methodology, illustrative data and our efforts toward a diagnostic classification scheme. In particular we will describe application of the Mahalanobis distance and related statistical methods to DLS data.

Photonic effects on mononuclear leukocytes

The effects of pulsed light (2 Hz) with a 55% duty ratio and continuous light on the migration of human mononuclear leukocytes, MNLs (monocytes and lymphocytes) are reported for red light ((lambda) equals 660 nm) and green light ((lambda) equals 565 nm). The comparison of the relative value of the distance to blood cell migration under light to the control cell migration without light stimulus is recorded as cytokinetic index, K.I. K.I. is a measure of the cytokinesis which is the progress of the cell movement in which the migration is enhanced by substances in the cell environment irrespective of a concentration gradient. Red light stimulation produces K.I.s for PMNs which are 30% grater than for MNLs. Green light stimulation produces K.I.s for PMNs less than 1.0 indicative of inhibited migration, while for MNLs the K.I.s are slightly greater than 1.0 indicative of enhanced migration.

Influence of light sources on the migration of polymorphonuclear leukocytes

In the process of inflammation, leukocytes must travel from the intraluminal space of the capillary to the interstitial space in order to reach the site of the inflammation. The two major populations of mature human leukocytes based on the morphology are the polymorphonuclear leukocytes (PMN), and mononuclear leukocytes (MNL). Previous research on PMNs and MNLs at the Biomedical Engineering and Science Institute of Drexel University have shown that their migration can be markedly enhanced by excitation with electric and magnetic fields. This presentation demonstrates that the migration of PMNs under excitation of photons is enhanced in the red light region of (lambda) equals 660 nm and inhibited in the green light region of (lambda) equals 565 nm. There is an intensity threshold at which red light enhances migration and an intensity threshold at which green light inhibits migration. In these experiments the Boyden technique was used with the distance of the cell migration through a cellulose filter measured in terms of the leading edge. The comparison of the relative value of the distance to cell migration under a light to cell migration without a light stimulus was recorded as a cytokinetic index, K.I.. K.I. is a measure of the cytokinesis which is the progress of the cell movement in which the migration is enhanced by substances in the cell environment irrespective of a concentration gradient. The cytotactic index is a measure of cytotaxis which is the directional movement along a chemical gradient formed by a chemotactic factor. A Russian pulsed commercial laser biostimulator in the near infrared wavelength above an intensity threshold enhances PMN migration. Intermittent green and red stimulators below the intensity threshold markedly influence the cytokinetic index of PMNs while above the intensity threshold, this influence is deminished.