Observational Clinical Studies of Human Lens Transparency Using the Vision Index Pen.

PURPOSE: Preventing or delaying the onset of presbyopia and cataract formation remains a challenge. The goal of this study was to establish the utility of the Vision Index Pen (VIP), designed to measure in vivo dynamic light scattering (DLS) from the crystalline lens, in the detection of early cataract or loss of accommodation and to show reproducibility through trials at two independent sites. The gradual loss of transparency of the lens was characterized by the lens crystallin aggregation index (LCX) derived from measured DLS data. METHODS: Volunteers in different age groups participated in two independently operated observational clinical studies. All subjects underwent a detailed eye exam and VIP measurement of the intensity correlation of the backscattered light from the lens. RESULTS: LCX values extracted from DLS data show strong correlation with the aging lens, ranging from 20 at the age of 20 years to over 150 at 60 years. Quantitatively significant changes in the LCX value occur from 35 years to 55 years. LCX values were found to correlate with the loss of accommodation (correlation of -0.563 with P < 0.001) and with published data regarding the change in relative lens resistance with age. CONCLUSIONS: Results from two independent observational clinical trials have confirmed the repeatability and reproducibility of the VIP diagnostic device as a viable clinical tool for tracking localized macromolecular changes taking place in the aging lens. Detection of early changes in the crystalline lens can be useful in developing patient-specific prediction models, which can be used to screen patients who may benefit from early therapeutic interventions for delaying the onset of presbyopia and cataract growth. TRANSLATIONAL RELEVANCE: The VIP diagnostic device provides in vivo access to the human lens, enabling characterization of the unfolding and decomposition of long-lived macromolecules.

Homodyne fiber optic backscatter dynamic light scattering.

Optical homodyne detection in the backscatter direction is achieved through a pair of collinearly located fibers in a cylindrical probe body. One fiber illuminates the scattering solution while the other fiber provides optical mixing of the backscattered optical field with a local oscillator derived from the Fresnel reflections at the glass interfaces of the sample container. Homodyne detection is possible over a broad range of particle size and sample concentration with a single probe design.

A dual detector capillary waveguide biosensor for detection and quantification of hybridized target.

We describe a novel technique for improving the sensitivity of analytical instruments based on the measurement of fluorescent intensity. Independent measurement of the Rayleigh scattered intensity component by means of a second photodetector leads to normalized data, which are independent of various experimental parameters. Incorporation of this technique into a fully automated capillary waveguide biosensor improved the instrument sensitivity by a factor of three. The technique enables quantification, as well as detection, of the hybridized target molecules.