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Leopold Schmetterer, Mengyuan Ke, Bingyao Tan, Damon Wong, Jacqueline Chua, Xinwen Yao; Assessment of Hyper-Parallel OCT to delineate corneal scar. Invest. Ophthalmol. Vis. Sci. 2020;61(9):PB0065.
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We report a case study of successfully detecting corneal scarring using a newly developed 3D spectral-domain (SD) OCT system called Hyper-Parallel OCT (HP-OCT) using ultrahigh speed acquisition, which reduces sensitivity to patient movement.
Anterior segment imaging was performed using the newly developed Cylite HP-OCT (Figure 1). The instrument employs a superluminescent laser diode centered at 840nm with a bandwidth of 25nm (axial resolution ~10um in tissue). It operates similarly to a SD OCT, except that it adopts two micro lens arrays. The incoming light is collimated by the first lenslet (400 um), forming a grid of beamlets which is scanned onto the sample. The inferemetric signals spatially separated by the second lenslet are dispersed by a diffraction grating and focused onto a 2D CCD camera with minimal cross-talking.The main advantage of HP-OCT is its ultrahigh speed, making it relatively insensitive to subjects’ movement. By dividing the incident beam into beamlets, this technique allows for higher incident power in the sample arm under the maximum permissible exposure limit, resulting in a better sensitivity. Fine lateral sampling resolution of 37um is achieved by dithered scan in the sample arm. A scan depth of approximate 8mm in tissue is acquired with more than 1000 simultaneous A-scans at rate of 300 frames/s.A patient with corneal opacity was scanned to produce a 16mm × 13.4mm × 8mm (427×357×1486 voxel) volumetric dataset. The volume was resliced into 32 different radial directions by a customized algorithm in MATLAB. A second scan was acquired in a 5mm × 2.9mm region containing the corneal scar using a high resolution objective lens giving the lateral resolution of 11um.
HP-OCT enables motion free, wide-field imaging of the cornea. As shown in Figure 2a the scleral spur is clearly discernable (yellow asterisk). Figure 2b-c show the corneal scar, which is clearly visible in the high-resolution image of the corneal stroma.
In summary, we demonstrated that HP-OCT is relatively insensitive to motion and can provide a wide-field corneal scan in a short acquisition time. This allow for visualization of corneal diseases such as scarring.
This is a 2020 Imaging in the Eye Conference abstract.
Figure 1. Schematic of HP-OCT.
Figure 2. Example of a wide-field corneal scan. (a) A radial scan converted from 3D volumetric data. (b) Magnified window of corneal scar. (c) High resolution image (5.5mm × 2.9mm) covering the cornea scar.
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