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Ewelina Pijewska, Kari V Vienola, Michal Meina, Pengfei Zhang, Ratheesh K. Meleppat, Maciej Szkulmowski, Ravi S Jonnal, Robert J Zawadzki; Extraction of phase-based optoretinograms (ORG) from serial B-scans acquired by clinical-grade raster scanning OCT system. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4081 – F0045.
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© ARVO (1962-2015); The Authors (2016-present)
To present application of the modified Knox-Thompson phase-based method for extraction of the light-evoked functional responses of human retina imaged with optical coherence tomography (OCT).
The human volunteers were imaged in vivo with a clinical-grade OCT retinal imaging system, equipped with a controlled light stimulator, to allow ORG experiments. Before the testing volunteers were dark-adapted for over 5 minutes. The clinical-grade OCTs cannot resolve individual photoreceptors and instead probe a group of cells, resulting in limited phase information due to temporal speckle decorrelation. Implementation of the modified Knox-Thompson method allowed us to successfully extract phase-based ORG signals from the outer segment band (between IS/OS and COST).
The phase-based ORG signals extracted from the same data sets, although more sensitive to retina motion and more computational demanding than ORG intensity-based methods, provided an order of magnitude higher sensitivity of detecting changes in retina layers positions. The cross-correlation of the phase difference between the measured layers of the object allowed identification of the intervals with strong phase correlation, thus allowing extraction of the ORG signal in a clinical setting.
Successful implementation of phase-based ORG signal analysis provided an order of magnitude higher sensitivity of detecting changes in retina layer positions. ORG signal analysis using clinical-grade raster scanning OCT systems is now possible, which should open a path to clinically friendly ORG probing.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
The reference measurement of retina activity in no light stimulus experiment (a-e). The retina response for visible light stimulation (f-j). (a,f) OCT B-scan with reference layers IS/OS and COST used to extract ORG signal; (b,g) time evolution of a phase difference of the averaged cross-spectrum, between two spatially separated layers, the representative position of windows is marked by the green rectangle in (a); (c,h) binary mask b to extract well-defined regions of phase cross-spectrum; (d, i) reduced weighted time evolution of a phase difference of the averaged cross-spectrum from (b); (e,j) time-dependent phase difference between two layers extracted using the Knox-Thompson paths.
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