June 2024 - Physical Sciences Inc.

Article

Relevant Publications on high-resolution retinal imaging using PSI instruments

M. Mujat, R.D. Ferguson, D.X. Hammer, A.H. Patel and N. Iftimia “High-Resolution Retinal Imaging: Technology Overview and Applications”, Photonics 11(6), 522. (2024)
M. Mujat, K. Sampani, A.H. Patel, R. Zambrano, J.K. Sun, G. Wollstein, R.D. Ferguson, J.S. Schuman, and N. Iftimia, “Motion Contrast, Phase Gradient, and Simultaneous OCT Images Assist in the Interpretation of Dark-Field Images in Eyes with Retinal Pathology”, Diagnostics, 14(2), 184. (2024)
M. Mujat, K. Sampani, A.H. Patel, J.K. Sun, and N. Iftimia, “Cellular-Level Analysis of Retinal Blood Vessel Walls Based on Phase Gradient Images”, Diagnostics, 13(22), 3399. (2023)
M. Mujat, J.D. Akula, A.B. Fulton, R.D. Ferguson, and N. Iftimia, “Non-Rigid Registration for High-Resolution Retinal Imaging”, Diagnostics, 13(13), 2285. (2023)
J.D. Akula, I.A. Arellano, E.A. Swanson, T. L. Favazza, T. S. Bowe, R. J. Munro, R. D. Ferguson, R.M. Hansen, A. Moskowitz, A.B. Fulton, “The Fovea in Retinopathy of Prematurity”, Invest. Ophthalmol. Vis. Sci., 61(11), 28 (2020)
M. Mujat, Y. Lu, G. Maguluri, Y. Zhao, N. Iftimia, and R.D. Ferguson, “Visualizing the vasculature of the entire human eye posterior hemisphere without a contrast agent”, Biomedical Optics Express, 10(1), 167-180, (2019)
K. Grieve,E. Gofas-Salas,R.D. Ferguson,J.A.Sahel,M. Paques,E.A.Rossi, “Invivonear-infraredautofluorescenceimagingofretinalpigmentepithelialcellswith757nmexcitation”,Biomed. Opt. Express, 9(12), 5946–5961 (2018)
R. Ramamirtham, J.D. Akula, G. Soni, M.J. Swanson, J.N. Bush, A. Moskowitz, E.A. Swanson, T.L. Favazza, J.L. Tavormina, M. Mujat, R.D. Ferguson, R.M. Hansen, and A.B. Fulton, “Extrafoveal Cone Packing in Eyes With a History of Retinopathy of Prematurity”, Invest. Ophthalmol. Vis. Sci., 57(2):467-475 (2016)
D.X. Hammer, R.D. Ferguson, M. Mujat, A. Patel, E. Plumb, N. Iftimia, T.Y.P. Chui, J.D. Akula, and A.B. Fulton, “Multimodal adaptive optics retinal imager: design and performance”, JOSA A., 29(12), 2589-2607(2012)
M. Mujat, R.D. Ferguson, A.H. Patel, N. Iftimia, N. Lue, and D.X. Hammer, “High resolution multimodal clinical ophthalmic imaging system”, Optics Express, 18(11), 11607-11621 (2010)
R.D. Ferguson, Z. Zhong, D.X. Hammer, M. Mujat, A.H. Patel, C. Deng, W. Zou, and S.A. Burns, “Adaptive optics scanning laser ophthalmoscope with integrated wide-field retinal imaging and tracking”, JOSA A., 27(12), A265-A277(2010)
M. Mujat, R.D. Ferguson, N. Iftimia, and D.X. Hammer, “Compact adaptive optics line scanning ophthalmoscope”, Optics Express, 17(12), 10242-10258 (2009)
S.A. Burns, R. Tumbar, A.E. Elsner, R.D. Ferguson, and D.X. Hammer, “Large-field-of-view,modular,stabilized,adaptive-optics-basedscanninglaserophthalmoscope”,JOSA A-Opt. Image Sci. Vision, 24(5), 1313–1326(2007)
C.E. Bigelow, N. Iftimia, R.D. Ferguson, T.E. Ustun, B. Bloom, and D.X. Hammer, “Compact multimodal adaptive-optics spectral-domain optical coherence tomography instrument for retinalimaging”,JOSA A-Opt. Image Sci. Vision, 24(5), 1327–1336 (2007)

Publications from our clinical collaborators including the use of PSI instruments

E. Gofas-Salas, D.M.W. Lee, C. Rondeau, K. Grieve, E.A. Rossi, M. Paques, and K. Gocho, “Comparison between Two Adaptive Optics Methods for Imaging of Individual Retinal Pigmented Epithelial Cells”, Diagnostics, 14(7), 768 (2024)
Z.M. Dong,G. Wollstein,B. Wang,J.S.Schuman, “Adaptiveopticsopticalcoherencetomographyinglaucoma”,Progress in Retinal and Eye Research (57), 76–88 (2017)

Publication

Abstract

Adaptive optics provides improved resolution in ophthalmic imaging when retinal microstructures need to be identified, counted, and mapped. In general, multiple images are averaged to improve the signal-to-noise ratio or analyzed for temporal dynamics. Image registration by cross-correlation is straightforward for small patches; however, larger images require more sophisticated registration techniques. Strip-based registration has been used successfully for photoreceptor mosaic alignment in small patches; however, if the deformations along strips are not simple displacements, averaging can degrade the final image. We have applied a non-rigid registration technique that improves the quality of processed images for mapping cones over large image patches. In this approach, correction of local deformations compensates for local image stretching, compressing, bending, and twisting due to a number of causes. The main result of this procedure is improved definition of retinal microstructures that can be better identified and segmented. Derived metrics such as cone density, wall-to-lumen ratio, and quantification of structural modification of blood vessel walls have diagnostic value in many retinal diseases, including diabetic retinopathy and age-related macular degeneration, and their improved evaluations may facilitate early diagnostics of retinal diseases.

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Published

June 3, 2024

Publication

Abstract

Diseases such as diabetes affect the retinal vasculature and the health of the neural retina, leading to vision problems. We describe here an imaging method and analysis procedure that enables characterization of the retinal vessel walls with cellular-level resolution, potentially providing markers for eye diseases. Adaptive optics scanning laser ophthalmoscopy is used with a modified detection scheme to include four simultaneous offset aperture channels. The magnitude of the phase gradient derived from these offset images is used to visualize the structural characteristics of the vessels. The average standard deviation image provides motion contrast and enables segmentation of the vessel lumen. Segmentation of blood vessel walls provides quantitative measures of geometrical characteristics of the vessel walls, including vessel and lumen diameters, wall thickness, and wall-to-lumen ratio. Retinal diseases may affect the structural integrity of the vessel walls, their elasticity, their permeability, and their geometrical characteristics. The ability to measure these changes is valuable for understanding the vascular effects of retinal diseases, monitoring disease progression, and drug testing. In addition, loss of structural integrity of the blood vessel wall may result in microaneurysms, a hallmark lesion of diabetic retinopathy, which may rupture or leak and further create vision impairment. Early identification of such structural abnormalities may open new treatment avenues for disease management and vision preservation. Functional testing of retinal circuitry through high-resolution measurement of vasodilation as a response to controlled light stimulation of the retina (neurovascular coupling) is another application of our method and can provide an unbiased evaluation of one’s vision and enable early detection of retinal diseases and monitoring treatment results.

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Published

June 3, 2024

Publication

Abstract

The cellular-level visualization of retinal microstructures such as blood vessel wall components, not available with other imaging modalities, is provided with unprecedented details by dark-field imaging configurations; however, the interpretation of such images alone is sometimes difficult since multiple structural disturbances may be present in the same time. Particularly in eyes with retinal pathology, microstructures may appear in high-resolution retinal images with a wide range of sizes, sharpnesses, and brightnesses. In this paper we show that motion contrast and phase gradient imaging modalities, as well as the simultaneous acquisition of depth-resolved optical coherence tomography (OCT) images, provide additional insight to help understand the retinal neural and vascular structures seen in dark-field images and may enable improved diagnostic and treatment plans.

© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Published

June 3, 2024

Publication

Abstract

Adaptive optics (AO) has been used in many applications, including astronomy, microscopy, and medical imaging. In retinal imaging, AO provides real-time correction of the aberrations introduced by the cornea and the lens to facilitate diffraction-limited imaging of retinal microstructures. Most importantly, AO-based retinal imagers provide cellular-level resolution and quantification of changes induced by retinal diseases and systemic diseases that manifest in the eye enabling disease diagnosis and monitoring of disease progression or the efficacy of treatments. In this paper, we present an overview of our team efforts over almost two decades to develop high-resolution retinal imagers suitable for clinical use. Several different types of imagers for human and small animal eye imaging are reviewed, and representative results from multiple studies using these instruments are shown. These examples demonstrate the extraordinary power of AO-based retinal imaging to reveal intricate details of morphological and functional characteristics of the retina and to help elucidate important aspects of vision and of the disruptions that affect delicate retinal tissue.

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Published

June 3, 2024