Ophthalmic imaging

LEFT: (A) Schematic of the portable OCT system and handheld imaging scanner.(B) Anatomy of the handheld OCT scanner. RIGHT:  Handheld imaging scanner functionality. (A, B) Photographs of handheld scanner with and without ear speculum tip, respectively. (C) Scanner attachments for retina, anterior segment/skin, oral mucosa, and ear, from left to right in the photo. (D, E) Photographs of the handheld scanner used for eye (D) and ear (E) imaging. LCD screen shows color video image and OCT cross-section simultaneously.

Quantitative measurements of the blood vessel diameter (BVD) and blood vessel number (BVN) for the retinas of MS patients. MS eyes have a lower total BVD and BVN than control eyes. The effect was more pronounced with increased MS disability, and persisted in multivariate models adjusting for retinal nerve fiber layer (RNFL) thickness and optic neuritis (ON) history.

Optical coherence tomography (OCT) has long been used as a diagnostic tool in the field of ophthalmology. The ability to observe microstructural changes in the tissues of the eye has proved very effective in diagnosing ocular disease. However, this technology has yet to be introduced into the primary care office, where indications of disease are first encountered. We have developed a portable, handheld imaging probe for use in the primary care setting and evaluated its tissue site accessibility, ability to observe diseased tissue, and screening capabilities in in vivo human patients, particularly for pathologies related to the eye.

Quantitative parameters can be extracted from the retinal images to be used as disease indicators. One such metric is the ratio of thicknesses between the many retinal cell layers. The is a robust metric that will not be affected by overall retinal thickness variation between patients. A ratiometric analysis of retinal layer thicknesses reveals a statistically different set of thickness ratio values for diabetic patients, as well as multiple sclerosis patients. A ratiometric analysis on layer thicknesses in the retina of diabetic and control patients reveals a statistically different set of thickness ratio values for diabetic patients. These results are encouraging for future efforts to diagnose or screen for diabetes at an early stage, before symptoms or gross retinal abnormalities occur. Previous studies have investigated layer thicknesses in the retina to draw conclusions about the presence of diabetes; however, an analysis of the ratios of these layer thicknesses is a more robust measure. Variations in overall retinal thickness between patients will not affect the accuracy of ratio measurements.

  • •Bhaduri B, Nolan RM, Shelton RL, Pilutti LA, Motl RW, Boppart SA. Ratiometric analysis of in vivo retinal layer thicknesses in multiple sclerosis. J Biomedcial Optics, 21:095001 2016. 
  • Bhaduri B, Nolan RM, Shelton RL, Pilutti LA, Motl RW, Pula JH, Boppart SA. Detection of retinal blood vessel volume loss in multiple sclerosis with optical coherence tomography . Biomedical Optics Express, 7:2321-2330 2016. 
  • Shemonski ND, Adie SG, South FA, Liu Y-Z, Carney PS, Boppart SA, "Computational high-resolution optical imaging of the living human retina," Nature Photonics, 9:440-443, 2015. 
  • Shelton R, Jung W, Sayegh SI, McCormick DT, Kim J, Boppart SA, "Optical coherence tomography for advanced screening in the primary care office," Journal of Biophotonics, 7:525-533, 2014. 
  • Shelton R, Tailb J, Shemonski N, Sayegh SI, Boppart SA, "Subretinal layer thickness ratio changes for early detection of diabetes," Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, Seattle, WA, May 5-9, 2013. 

Adaptive optics for ophthalmic imaging 

High-resolution in vivo imaging is of great importance for the fields of biology and medicine. The introduction of hardware- based adaptive optics (HAO) has pushed the limits of optical imaging, enabling high-resolution near diffraction-limited imaging of previously unresolvable structures. In ophthalmology, when combined with optical coherence tomography, HAO has enabled a detailed three-dimensional visualization of photoreceptor distributions and individual nerve fibre bundles in the living human retina. However, the introduction of HAO hardware and supporting software adds considerable complexity and cost to an imaging system, limiting the number of researchers and medical professionals who could benefit from the technology. Whave demonstrated a fully automated computational approach that enables high-resolution in vivo ophthalmic imaging without the need for HAO. Our results highlight that computational methods in coherent microscopy are applicable in highly dynamic living systems.

  • Shemonski ND, South FA, Liu Y-Z, Adie SG, Carney PS, Boppart SA. Computational high-resolution optical imaging of the living human retina.   Nature Photonics, 9:440-443, 2015. 2015.

Functional retinal OCT

In this work, a quantitative analysis of retinal blood vessels from OCT scans was performed in order discover a potential indicator for disease progression of multiple sclerosis. Two future studies were conducted using retinal layer thicknesses as the potential predictor for disease. In these studies, retinal images captured with OCT were segmented by layer to generate quantitative metrics for comparison. Novel ratiometric analyses were subsequently performed to validate the utility of layer thicknesses as predictive factors for both multiple sclerosis and diabetic retinopathy.

  • B. Bhaduri, R. M. Nolan, R. L. Shelton, L. A. Pilutti, R. W. Motl, H. E. Moss, J. H. Pula, & S. A. Boppart, “Detection of retinal blood vessel changes in multiple sclerosis with optical coherence tomography,” Biomedical Optics Express, vol. 7, no. 6, p. 2321, Jun. 2016, doi: 10.1364/BOE.7.002321.
  • B. Bhaduri, R. M. Nolan, R. L. Shelton, L. A. Pilutti, R. W. Motl, & S. A. Boppart, “Ratiometric analysis of in vivo retinal layer thicknesses in multiple sclerosis,” Journal of Biomedical Optics, vol. 21, no. 09, p. 1, Sep. 2016, doi: 10.1117/1.JBO.21.9.095001.
  • B. Bhaduri, R. L. Shelton, R. M. Nolan, L. Hendren, A. Almasov, L. T. LabriolaS. A. Boppart, “Ratiometric analysis of optical coherence tomography-measured in vivo retinal layer thicknesses for the detection of early diabetic retinopathy,” Journal of Biophotonics, vol. 10, no. 11, pp. 1430–1441, Nov. 2017, doi: 10.1002/jbio.201600282.