Comparison of anterior segment optical coherence tomography angiography systems for corneal vascularisation

Ang, Marcus; Devarajan, Kavya; Das, Suchandrima; Stanzel, Tisha Prabriputaloong; Tan, Anna; Girard, M; Schmetterer, Leopold; Mehta, Jodhbir S.

doi:10.1136/bjophthalmol-2017-311072

Cited by 41 publications

(45 citation statements)

References 19 publications

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“…A polychromatic X-ray beam [67][68][69] . From this the deviatoric lattice strain (~1 × 10 -3 ), lattice rotation (~1 × 10 -3 rads) and the GND density for each point was found 47,48,70,71 . Analysis of the Kikuchi patterns was carried out using the XEBSD code provided by A. J. Wilkinson 44 .…”

Section: Micro-beam Laue Diffractionmentioning

confidence: 99%

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

Das

Tarleton

et al. 2019

SSRN Journal

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Tungsten is the main candidate material for plasma-facing armour components in future fusion reactors. In-service, fusion neutron irradiation creates lattice defects through collision cascades. Helium, injected from plasma, aggravates damage by increasing defect retention.Both can be mimicked using helium-ion-implantation. In a recent study on 3000 appm heliumimplanted tungsten (W-3000He), we hypothesized helium-induced irradiation hardening, followed by softening during deformation. The hypothesis was founded on observations of large increase in hardness, substantial pile-up and slip-step formation around nano-indents and Laue diffraction measurements of localised deformation underlying indents. Here we test this hypothesis by implementing it in a crystal plasticity finite element (CPFE) formulation, simulating nano-indentation in W-3000He at 300 K. The model considers thermally-activated dislocation glide through helium-defect obstacles, whose barrier strength is derived as a function of defect concentration and morphology. Only one fitting parameter is used for the simulated helium-implanted tungsten; defect removal rate. The simulation captures the localised large pile-up remarkably well and predicts confined fields of lattice distortions and geometrically necessary dislocation underlying indents which agree quantitatively with previous Laue measurements. Strain localisation is further confirmed through high resolution electron backscatter diffraction and transmission electron microscopy measurements on crosssection lift-outs from centre of nano-indents in W-3000He.

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Section: Micro-beam Laue Diffractionmentioning

confidence: 99%

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

Das

Tarleton

et al. 2019

SSRN Journal

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“…The machine uses SSADA to improve the performance of the vessel segmentation algorithm. 16 For imaging, the anterior segment lens adapter was used with the Angiovue scan protocol of the OCTA device (6.00 3 6.00 mm; AngioRetina). The eye tracking and autofocus functions were deactivated, and the lens moved close to the corneal surface before manual adjustments to the Z-motor positioning and focal length were made to achieve precise focus on the B-scan area of interest.…”

Section: Methodsmentioning

confidence: 99%

“…The eye tracking and autofocus functions were deactivated, and the lens moved close to the corneal surface before manual adjustments to the Z-motor positioning and focal length were made to achieve precise focus on the B-scan area of interest. 16 Anterior segment scans centered at the CAG area and the harvested area were obtained at 1 week and 1 and 3 months postoperatively by a trained operator (K.D.). We assessed vessel density at 3 depths: the conjunctival and CAG epithelium (w50 mm), the conjunctival stroma and CAG (w70-130 mm), and the episclera (w230-300 mm) at the CAG and harvested sites, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The speckle noise was removed using median filtering and Gaussian smoothing, and top-hat filtering was used to improve the signal-to-noise ratio while preserving the image features. 16 Local phase-based filter for optimal enhancement of segmented vessels was applied, thereafter, where an infinite perimeter active contour model to partition the enhanced image into a binary image (vessel pixels, 1; background, 0) was performed. 16 After binarization, the binarized image from the previous follow-up scan was subtracted from the new consecutive follow-up binarized image.…”

Section: Methodsmentioning

confidence: 99%

“…16 Local phase-based filter for optimal enhancement of segmented vessels was applied, thereafter, where an infinite perimeter active contour model to partition the enhanced image into a binary image (vessel pixels, 1; background, 0) was performed. 16 After binarization, the binarized image from the previous follow-up scan was subtracted from the new consecutive follow-up binarized image. The vessel density percentage computed in the binary subtracted image between consecutive follow-ups was defined as the vessel regrowth density percentage, as shown in the following equations: Vessels regrowth density percentage ¼ Vessels density percentage at follow-up (n þ1) À Vessels density percentage at follow-up (n), where:…”

Section: Methodsmentioning

confidence: 99%

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Optical Coherence Tomography Angiography for Evaluation of Reperfusion After Pterygium Surgery

Liu

Devarajan

Tan

et al. 2019

American Journal of Ophthalmology

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PURPOSE: To describe the use of optical coherence tomography angiography (OCTA) to quantitatively monitor the conjunctival graft revascularization after pterygium excision and conjunctival autograft (CAG) transplantation.DESIGN: Prospective, interventional case series. METHODS: Ten patients undergoing pterygium excision and femtosecond laser-assisted CAG transplantation were included. OCTA was performed at 1 week, 1 and 3 months postoperatively at the CAG transplantation site and harvested area. The vessel density at three different depths: conjunctival epithelium or CAG epithelium, conjunctival stroma or CAG stroma, and episclera, was evaluated and quantified. The revascularization rate was assessed and correlated with the postoperative CAG thickness. RESULTS: No intraoperative and postoperative complications occurred. Reperfusion of the CAGs was observed at 1 week, and early reperfusion within the first month accounted for more than half of graft revascularization. The vessel regrowth density was 9.6±2.6 % and 11.1±2.8 % between 1 week and 1 month, and was 9.8±1.8 % and 11.9±1.9 % between 1 and 3 months, at the CAG and underlying episcleral levels, respectively. All the CAGs were well-perfused at 3 months. The vessel regrowth density was significantly and strongly correlated with the changes of CAG thickness in a negative relationship (g [ -0.94, P [ 0.019). At the harvested site, the vascular network of episclera was not affected, and the conjunctival vascularization was restored at 1 month. CONCLUSIONS: OCTA is a promising tool to evaluate the vascularization or revascularization of conjunctiva, conjunctival graft and episclera, in a quantitative and serial manner, helping in diseases diagnosis and treatment monitoring. The graft revascularization rate was predictive of postoperative graft deswelling.

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Optical Coherence Tomography Angiography

Wang

Miller

2022

Albert and Jakobiec's Principles and Practice of Ophthalmology

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Comparison of anterior segment optical coherence tomography angiography systems for corneal vascularisation

Cited by 41 publications

References 19 publications

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

Optical Coherence Tomography Angiography for Evaluation of Reperfusion After Pterygium Surgery

Optical Coherence Tomography Angiography

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