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U.S. Department of Health and Human Services

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Research Project: Optical Biosensing and Biomaging Technology for Safety and Performance Evaluation in Biophotonics and Nanobiophotonics

This key research project focuses on investigating multifunctional combined biosensing and bioimaging technologies to establish performance metrics and standardized laser safety test methodologies (including high-resolution OCT and confocal microscopy) that can be used in the application of these technologies in medical devices. 

Task 1: Advanced Test Methods for Laboratory Evaluation of Intraocular Lens (IOL) Implants

Principal Investigators:
Robert James, MS (contact: robert.james@fda.hhs.gov)
Do-Hyun Kim, PhD
Ilko K Ilev, PhD

Collaborators:
James Anderson
Michael Roberts
Sindhoora Murthy

Abstract:
This research program is designed to evaluate the various parameters of intra-ocular lens (IOL) implants, such as dioptric power, resolution, scattering and glare, and to utilize the results to develop improved test methods for IOL standards. IOLs are artificial replacements for the natural lens of the eye, which frequently becomes clouded due to cataract formation. There are approximately 3 million surgeries per year in the US at a cost of 3 billion dollars.

Intraocular lenses are an evolving technology, with recent trends of softer, foldable, materials allowing smaller incisions for implantation. New lens designs are constantly being introduced, including aphakic, phakic (as an alternative to refractive surgery), multifocal, accomodative, toric, and light adjustable (for power) lenses. These advances can create new issues to be evaluated, such as accuracy of dioptric power and lens inclusions which may result in poor quality of vision, possibly requiring explantation. The CDRH ODE needed assurance that lenses are not defective, and needed improved test methods to properly evaluate these issues.

DP determined that the current methods described in the ANSI standard for IOLs were inadequate to identify some of these optical quality defects. This project has several objectives, which includes the development of a standard test method for dioptric power. This method is based on a simple fiber-optic confocal laser design, which includes a single-mode fiber coupler that serves simultaneously as a point light source used for formation of a collimated Gaussian laser beam, and as a sensitive confocal point receiver. This method provides an accurate, repeatable, objective, and fast method for dioptric power measurement of IOLs. It is useful to measure both positive and negative power IOLs over the range of 0D to 30 D. Its accuracy and precision are superior to current methods, having an accuracy of less than 1 um in focal length, and precision of less than 0.01 D. It has been presented to be included in IOL consensus standards. The Figure below illustrates the concept. DP is also developing a variation on the dioptic power scheme to measure other IOL physical parameters, such as the refractive index, thickness and geometrical shape of IOLs.

Additionally, new IOL materials frequently will exhibit increased levels of glare and scattering, which can lead to reduced quality of vision and, in some cases, lens explantations. Scattering is caused by inclusions in the lens material, which are called glistenings or vacuoles. DP is developing several complementary methods for precisely testing IOL scatter, including photographic analysis, fiber-optically collimated laser beam, integrating sphere studies, and mathematical modeling. The Figure (a) below illustrates an IOL with a relatively high density of vacuoles. Glare is any unwanted light/dark image in vision, which can include streaks of light, rays from a central point source of light, bright line/lines, cobweb like rays of light, and subjective darkness or shadow. It is common to all IOL types. DP is developing a test method to quantify glare from IOLs based on a fiber-optically collimated laser beam and a model eye which is mounted on positioning stages to allow displacement and rotation of the model eye. The Figure (b) below indicates a visual images resulting from IOL glare, which has been tested using the single-mode fiber based setup presented in Figure (c). 

Task 2: High-Resolution OCT and Confocal Microscopy Methods in Multifunctional Bioimaging and Biosensing Applications

Principal Investigators:
Ilko K Ilev, PhD (contact: ilko.ilev@fda.hhs.gov)
Do-Hyun Kim, PhD

Collaborators:
Keith Petrillo
Will Calhoun

Abstract:
The primary objective of this project is to investigate fundamental principles, basic advantages and critical limitations of novel approaches in multifunctional bioimaging and biosensing using high-resolution optical coherence tomography (OCT) and confocal microscopy systems. The study includes the following research aims:

  1. Evaluating safety and effectiveness of new optical therapeutic technologies and devices concerning critical optical parameters and safety issues related to various medical therapeutic lasers, fiber-optic technologies and new therapeutic monitoring and biosensing systems
  2. Developing and investigating the effectiveness and critical performance characteristics of OCT-based methods for novel combined imaging and sensing applications in the areas of ophthalmology, optical nerve stimulation and biochemical analysis
  3. OCT monitoring and evaluating the effectiveness of corneal cutting and ablation performance of various ultrashort femtosecond laser refractive and cataract surgical procedures
  4. Monitoring and evaluating the safety and effectiveness of optical stimulation of single neurons and nerve tissue
  5. Developing independent OCT-based test methods for detecting and monitoring of biochemical contaminations on medical device surfaces
  6. Developing and investigating advanced multifunctional fiber-optic confocal microscope methods with combined potential monitoring, biosensing and therapy of single cells and tissues
  7. Developing fiber-optic-based confocal nanoscope imaging systems that provide three-dimensional imaging with an ultrahigh spatial resolution in the subwavelength nanometric scale beyond the diffraction limit (below 100 nm)

Figures below illustrate some of our recent proof-of-concept results on OCT guided optical nerve stimulation (a), a noninvasive OCT 3-D volumetric quality evaluation of post-surgical corneal incisions (b), an ultrahigh-resolution fiber-optic confocal method for imaging beyond the diffraction limit in the nanometric scale (c), and novel approaches for fiber-optic biosensing (d).