Purpose Compare performance of normalized reflectance index (NRI) and retinal nerve fiber layer thickness (RNFLT) parameters determined from OCT images for glaucoma and glaucoma suspect diagnosis. Methods Seventy-five eyes from seventy-one human subjects were studied: 33 controls, 24 glaucomatous, and 18 glaucoma-suspects. RNFLT and NRI maps were measured using two custom-built OCT systems and the commercial instrument RTVue. Using area under the receiver operating characteristic (ROC) curve, RNFLT and NRI measured in seven RNFL locations were analyzed to distinguish between control, glaucomatous, and glaucoma-suspect eyes. Results The mean NRI of the control group was significantly larger than the means of glaucomatous and glaucoma-suspect groups in most RNFL locations for all three OCT systems (p<0.05 for all comparisons). NRI performs significantly better than RNFLT at distinguishing between glaucoma-suspect and control eyes using RTVue OCT (p=0.008). The performances of NRI and RNFLT for classifying glaucoma-suspect vs. control eyes were statistically indistinguishable for PS-OCT-EIA (p=0.101) and PS-OCT-DEC (p=0.227). The performances of NRI and RNFLT for classifying glaucomatous vs. control eyes were statistically indistinguishable (PS-OCT-EIA: p=0.379; PS-OCT-DEC: p=0.338; RTVue OCT: p=0.877). Conclusions NRI is a promising measure for distinguishing between glaucoma-suspect and control eyes and may indicate disease in the pre-perimetric stage. Results of this pilot clinical study warrant a larger study to confirm the diagnostic power of NRI for diagnosing pre-perimetric glaucoma.

Improving lateral resolution for cross-sectional optical coherence tomography (OCT) imaging is difficult due to the rapid divergence of light once it is focused to a small spot. To overcome this obstacle, we introduce a fiber optics system that generates a coaxially focused multimode (CAFM) beam for depth of focus (DOF) extension. We fabricated a CAFM beam OCT probe and show that the DOF is more than fivefold that of a conventional Gaussian beam, enabling cross-sectional imaging of biological tissues with clearly resolved cellular and subcellular structures over more than a 400 μm depth range. The compact and straightforward design and high-resolution extended DOF imaging capabilities of this technique suggests that it will be very useful for endoscopic cross-sectional imaging of human internal organs in vivo.

We report the design and fabrication of a flexible, longitudinally scanning high-resolution micro-optical coherence tomography (μOCT) endobronchial probe, optimized for micro-anatomical imaging in airways. The 2.4 mm diameter and flexibility of the probe allows it to be inserted into the instrument channel of a standard bronchoscope, enabling real-time video guidance of probe placement. To generate a depth-of-focus enhancing annular beam, we utilized a new fabrication method, whereby a hollow glass ferrule was angle-polished and gold-coated to produce an elongated annular reflector. We present validation data that verifies the preservation of linear scanning, despite the use of flexible materials. When utilized on excised, cultured mouse trachea, the probe acquired images of comparable quality to those obtained by a benchtop μOCT system.

Optical coherence tomography (OCT) is an attractive medical modality due to its ability to acquire high-resolution, cross-sectional images inside the body using flexible, small-diameter, scanning fiber optic probes. Conventional, cross-sectional OCT imaging technologies have approximately 10-μm axial resolution and 30-μm lateral resolution, specifications that enable the visualization of microscopic architectural morphology. While this resolution is useful for many clinical applications, it is insufficient for resolving individual cells that characterize many diseases. To address this gap, a supercontinuum-laser-based, μm-resolution OCT (μOCT) system and a 500 μm-diameter, extended depth of focus single fiber optic probe for endoscopic and intravascular imaging were designed and fabricated. At the distal tip of the fiber optic probe, a cylindrical waveguide was used to divide the wavefront to provide multiple circular propagation modes. Once transmitted through a relatively high NA lens (NA >0.1), these modes were projected as multiple coaxial foci (~3 μm full width at half maximum (FWHM)) over a greatly extended focal depth range. The distal tip of the probe also contained a common-path reference reflectance to minimize polarization and dispersion imbalances between sample and reference arm light. Measurements showed that the probe provides a 20-fold depth of focus extension, maintaining a 3-5 µm lateral resolution (FWHM of PSF) and a 2 μm axial resolution over a depth range of approximately 1 mm. These results suggest that this new optical configuration will be useful for achieving high-resolution, cross-sectional OCT imaging in catheter/endoscope-based medical imaging devices.