Imaging and Diagnostics

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Kim J, Men CJ, Ratanawongphaibul K, Papadogeorgou G, Tsikata E, Ben-David GS, Antar H, Poon LY, Freeman M, Park EA, Guzman Aparicio MA, de Boer JF, Chen TC. Reproducibility of Neuroretinal Rim Measurements Obtained from High-Density Spectral Domain Optical Coherence Tomography Volume Scans. Clin Ophthalmol 2022;
Kras A, Celi LA, Miller JB. Accelerating ophthalmic artificial intelligence research: the role of an open access data repository. Curr Opin Ophthalmol 2020;31(5):337-350.Abstract
PURPOSE OF REVIEW: Artificial intelligence has already provided multiple clinically relevant applications in ophthalmology. Yet, the explosion of nonstandardized reporting of high-performing algorithms are rendered useless without robust and streamlined implementation guidelines. The development of protocols and checklists will accelerate the translation of research publications to impact on patient care. RECENT FINDINGS: Beyond technological scepticism, we lack uniformity in analysing algorithmic performance generalizability, and benchmarking impacts across clinical settings. No regulatory guardrails have been set to minimize bias or optimize interpretability; no consensus clinical acceptability thresholds or systematized postdeployment monitoring has been set. Moreover, stakeholders with misaligned incentives deepen the landscape complexity especially when it comes to the requisite data integration and harmonization to advance the field. Therefore, despite increasing algorithmic accuracy and commoditization, the infamous 'implementation gap' persists. Open clinical data repositories have been shown to rapidly accelerate research, minimize redundancies and disseminate the expertise and knowledge required to overcome existing barriers. Drawing upon the longstanding success of existing governance frameworks and robust data use and sharing agreements, the ophthalmic community has tremendous opportunity in ushering artificial intelligence into medicine. By collaboratively building a powerful resource of open, anonymized multimodal ophthalmic data, the next generation of clinicians can advance data-driven eye care in unprecedented ways. SUMMARY: This piece demonstrates that with readily accessible data, immense progress can be achieved clinically and methodologically to realize artificial intelligence's impact on clinical care. Exponentially progressive network effects can be seen by consolidating, curating and distributing data amongst both clinicians and data scientists.
Kunkler AL, Patel NA, Russell JF, Fan KC, Al-Khersan H, Iyer PG, Acon D, Negron CI, Yannuzzi NA, Berrocal AM. Intraoperative OCT Angiography in Children with Incontinentia Pigmenti. Ophthalmol Retina 2022;6(4):330-332.
Kuo AN, Cortina MS, Greiner MA, Li JY, Miller DD, Shtein RM, Veldman PB, Yin J, Kim SJ, Shen JF. Advanced Corneal Imaging in Keratoconus: A Report by the American Academy of Ophthalmology. Ophthalmology 2024;131(1):107-121.Abstract
PURPOSE: To review the published literature on the diagnostic capabilities of the newest generation of corneal imaging devices for the identification of keratoconus. METHODS: Corneal imaging devices studied included tomographic platforms (Scheimpflug photography, OCT) and functional biomechanical devices (imaging an air impulse on the cornea). A literature search in the PubMed database for English language studies was last conducted in February 2023. The search yielded 469 citations, which were reviewed in abstract form. Of these, 147 were relevant to the assessment objectives and underwent full-text review. Forty-five articles met the criteria for inclusion and were assigned a level of evidence rating by the panel methodologist. Twenty-six articles were rated level II, and 19 articles were rated level III. There were no level I evidence studies of corneal imaging for the diagnosis of keratoconus found in the literature. To provide a common cross-study outcome measure, diagnostic sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were extracted. (A perfect diagnostic test that identifies all cases properly has an AUC of 1.0.) RESULTS: For the detection of keratoconus, sensitivities for all devices and parameters (e.g., anterior or posterior corneal curvature, corneal thickness) ranged from 65% to 100%. The majority of studies and parameters had sensitivities greater than 90%. The AUCs ranged from 0.82 to 1.00, with the majority greater than 0.90. Combined indices that integrated multiple parameters had an AUC in the mid-0.90 range. Keratoconus suspect detection performance was lower with AUCs ranging from 0.66 to 0.99, but most devices and parameters had sensitivities less than 90%. CONCLUSIONS: Modern corneal imaging devices provide improved characterization of the cornea and are accurate in detecting keratoconus with high AUCs ranging from 0.82 to 1.00. The detection of keratoconus suspects is less accurate with AUCs ranging from 0.66 to 0.99. Parameters based on single anatomic locations had a wide range of AUCs. Studies with combined indices using more data and parameters consistently reported high AUCs. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
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Le R, Cui Y, Lu ES, Zhu Y, Garg I, Wang JC, Lu Y, Zeng R, Katz R, Laíns I, Eliott D, Husain D, Kim LA, Miller JB. Prevalence of venous loops and association with retinal ischemia in diabetic retinopathy using widefield swept-source OCT angiography. Graefes Arch Clin Exp Ophthalmol 2023;Abstract
PURPOSE: To investigate the prevalence and clinical characteristics of diabetic patients with retinal venous loops (RVLs) and to assess the association with retinal ischemia using widefield swept-source optical coherence tomography angiography (WF SS-OCTA). METHODS: In this retrospective, cross-sectional study, a total of 195 eyes of 132 diabetic patients (31 eyes with no diabetic retinopathy (DR), 76 eyes with nonproliferative DR (NPDR), and 88 eyes with proliferative DR (PDR)) were imaged with WF SS-OCTA using Angio 6 × 6 mm and Montage 15 × 15 mm scans. Quantitative ischemia-related parameters, including ischemia index (ratio of nonperfusion area to total retinal area), foveal avascular zone (FAZ), and neovascularization features, were evaluated. RVLs were classified as type I or type II according to the branching level of the feeder vessel. A multivariate generalized estimating equations (GEE) logistic regression model was used to analyze the association of systemic parameters and ischemia-related metrics with RVLs in PDR eyes. RESULTS: Forty-eight RVLs were identified in 22 eyes (11.28%). The prevalence of RVLs was higher in PDR compared to NPDR eyes (21.59% vs. 3.95%, P < 0.05). Type II RVLs accounted for a higher proportion than type I (89.58% vs. 10.42%, P < 0.001). RVLs were more likely to originate from superior (vs. inferior) and temporal (vs. nasal) veins (P < 0.05). The GEE model showed that neovascularization (NV) flow area and diastolic blood pressure were associated with RVLs in the PDR group (P < 0.05). CONCLUSION: WF SS-OCTA is useful for the identification of RVLs in patients with DR. NV flow area and diastolic blood pressure were associated with the presence of RVLs in eyes with PDR. Ischemia index, FAZ, and other WF SS-OCTA parameters were not associated with RVLs. Further longitudinal studies are needed to identify the role of RVLs in DR progression.
Lu Y, Cui Y, Zhu Y, Lu ES, Zeng R, Garg I, Katz R, Le R, Wang JC, Vavvas DG, Husain D, Miller JW, Wu D, Miller JB. Quantitative Wide-Field Swept-Source Optical Coherence Tomography Angiography and Visual Outcomes in RAO. Clin Ophthalmol 2023;17:2505-2513.Abstract
PURPOSE: Retinal artery occlusion (RAO) is an ophthalmic emergency that can lead to poor visual outcomes and is associated with an increased risk of stroke and cardiovascular events. Wide-field swept-source OCT-A (WF SS-OCTA) can provide quick and non-invasive angiographic information with a wide field of view. Here, we looked for associations between OCT-A vascular imaging metrics and vision in RAO patients. METHODS: Patients with diagnoses of central (CRAO) or branched retinal artery occlusion (BRAO) were included. 6mm × 6mm Angio and 15mm × 15mm AngioPlex Montage OCT-A images were obtained for both eyes in each patient using Zeiss Plex Elite 9000 WF SS-OCTA device. Each 6mm × 6mm image was divided into nine Early Treatment Diabetic Retinopathy Study (ETDRS) subfields. Non-perfusion area (NPA) was manually measured using 15mm × 15mm images. A linear regression model was utilized to identify correlation between imaging metrics and vision. P-values less than 0.05 were considered as statistically significant. RESULTS: Twenty-five subjects were included. For RAO eyes, there was a statistically significant inverse correlation between retinal thickness as well as superficial capillary plexus (SCP) vessel density (VD) and vision. An inverse correlation was found between deep capillary plexus (DCP) VD and vision without statistical significance. There was a positive correlation between choroidal thickness as well as choroidal volume and vision without statistical significance. No significant correlation was found between the metrics and vision in contralateral eyes. For NPA and vision, no significant correlation was identified. CONCLUSION: This is the first study to investigate the utility of WF SS-OCTA in RAO and to demonstrate correlations between retinal vascular imaging metrics and visual outcomes. The results of this study provide a basis to understand the structural changes involved in vision in RAO and may guide management of RAO and prevention of cerebral stroke and cardiovascular accidents.
Lu Y, Wang JC, Cui Y, Zhu Y, Zeng R, Lu ES, Katz R, Husain D, Vavvas DG, Kim LA, Miller JW, Miller JB. A quantitative comparison of four optical coherence tomography angiography devices in healthy eyes. Graefes Arch Clin Exp Ophthalmol 2021;259(6):1493-1501.Abstract
PURPOSE: Optical coherence tomography angiography (OCT-A) is a novel imaging modality for the diagnosis of chorioretinal diseases. A number of FDA-approved OCT-A devices are currently commercially available, each with unique algorithms and scanning protocols. Although several published studies have compared different combinations of OCT-A machines, there is a lack of agreement on the consistency of measurements across OCT-A devices. Therefore, we conducted a prospective quantitative comparison of four available OCT-A platforms. METHODS: Subjects were scanned on four devices: Optovue RTVue-XR, Heidelberg Spectralis OCT2 module, Zeiss Plex Elite 9000 Swept-Source OCT, and Topcon DRI-OCT Triton Swept-Source OCT. 3 mm × 3 mm images were utilized for analysis. Foveal avascular zone (FAZ) area was separately and independently measured by two investigators. Fractal dimension (FD), superficial capillary plexus (SCP), and deep capillary plexus (DCP) vessel densities (VD) were calculated from binarized images using the Fiji image processing software. SCP and DCP VD were further calculated after images were skeletonized. Repeated measures ANOVA, post hoc tests, and interclass correlation coefficient (ICC) were performed for statistical analysis. RESULTS: Sixteen healthy eyes from sixteen patients were scanned on the four devices. Images of five eyes from the Triton device were excluded due to poor image quality; thus, the authors performed two sets comparisons, one with and one without the Triton machine. FAZ area showed no significant difference across devices with an ICC of > 95%. However, there were statistically significant differences for SCP and DCP VD both before and after skeletonization (p < 0.05). Fractal analysis revealed no significant difference of FD at the SCP; however, a statistically significant difference was found for FD at the DCP layer (p < 0.05). CONCLUSIONS: The results showed that FAZ measurements were consistent across all four devices, while significant differences in VD and FD measurements existed. Therefore, we suggest that for both clinical follow-up and research studies, FAZ area is a useful parameter for OCT-A image analysis when measurements are made on different machines, while VD and FD show significant variability when measured across devices.
Lu ES, Cui Y, Le R, Zhu Y, Wang JC, Laíns I, Katz R, Lu Y, Zeng R, Garg I, Wu DM, Husain D, Kim LA, Miller JB. Widefield swept-source optical coherence tomography angiography metrics associated with neovascular glaucoma in patients with proliferative diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol 2023;Abstract
PURPOSE: To explore the association between widefield swept-source optical coherence tomography angiography (WF SS-OCTA) metrics, including nonperfusion area (NPA) and neovascularization (NV), and presence of neovascular glaucoma (NVG) in patients with proliferative diabetic retinopathy (PDR). METHODS: A prospective, cross-sectional study was conducted from November 2018 to February 2020. A total of 85 eyes of 60 PDR patients without NVG and 9 eyes of 8 PDR patients with NVG were included. Retinal ischemic parameters (NPA; ischemia index [NPA/total retinal area]) and NV features (NV number; NV area; NV vessel density) were evaluated. Foveal avascular zone (FAZ), macular thickness/volume, and choroidal thickness/volume were obtained using the Zeiss ARI Network. WF SS-OCTA retinal and choroidal metrics, systemic, and ocular parameters were screened using Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression for variable selection. Firth's bias-reduced logistic regression (outcome: presence of NVG) was subsequently used to identify parameters associated with NVG. RESULTS: After LASSO variable selection, 8 variables were significantly associated with the presence of NVG: DM duration (years), insulin (yes/no), best-corrected visual acuity (BCVA) (logMAR), IOP, ischemia index, skeletonized vessel density, macular thickness (inner inferior, outer temporal regions). Firth's bias-reduced logistic regression showed ischemia index (odds ratio [OR]=13.2, 95% confidence interval [CI]:5.3-30.7, P<0.001) and BCVA (OR=5.8, 95%CI:1.2-28.8, P<0.05) were associated with the presence of NVG. NV metrics, FAZ, and choroidal parameters were not related to NVG. CONCLUSIONS: Retinal ischemia but not NV was associated with the presence of NVG in patients with PDR using WF SS-OCTA. Larger, longitudinal studies are needed to validate imaging biomarkers associated with diabetic NVG.
Lu N-J, Hafezi F, Koppen C, Alió Del Barrio JL, Aslanides IM, Awwad ST, Ní Dhubhghaill S, Pineda R, Torres-Netto EA, Wang L, Chen S-H, Cui L-L, Rozema JJ. New keratoconus staging system based on OCT. J Cataract Refract Surg 2023;49(11):1098-1105.Abstract
PURPOSE: To establish a numerical spectral-domain optical coherence tomography (SD-OCT)-based keratoconus (KC) staging system and compare it with existing KC staging systems. SETTING: Eye Hospital of Wenzhou Medical University, Wenzhou, China. DESIGNS: Retrospective case-control study. METHODS: Scheimpflug tomography, air-puff tonometry, and SD-OCT were performed on 236 normal and 331 KC eyes. All SD-OCT-derived parameters of the corneal epithelium and stroma were evaluated based on their receiver operating characteristic (ROC) curves, area under the curve (AUC), sensitivity, and specificity to discriminate between normal and KC eyes. The best performing parameters were subsequently used to create an OCT-based staging system, which was compared with existing tomographic and biomechanical staging systems. RESULTS: 236 eyes from 236 normal patients and 331 eyes from 331 KC patients of different stages were included. The highest ranked AUC ROC SD-OCT parameters, derived from stroma and epithelium, were stroma overall minimum thickness (ST: AUC 0.836, sensitivity 90%, specificity 67%) and epithelium overall SD (EP: AUC 0.835, sensitivity 75%, specificity 78%). A numerical SD-OCT staging system called STEP including 2 parameters-"ST" and "EP"-with 5 stages was proposed. CONCLUSIONS: The new SD-OCT-based KC staging system is the first to take the epithelium with its sublayer stroma information into account, showing a strong agreement to the existing staging systems. This system could be incorporated into daily practice, potentially leading to an overall improvement in KC treatment and follow-up management.
Lu Y, Wang JC, Zeng R, Nagata T, Katz R, Mukai S, Miller JB. Detection of retinal microvascular changes in von Hippel-Lindau disease using optical coherence tomography angiography. PLoS One 2020;15(2):e0229213.Abstract
PURPOSE: Von Hippel-Lindau (VHL) disease is a hereditary disorder that can lead to ophthalmic manifestations, including retinal capillary hemangioma (RCH). The diagnosis of RCH is often guided by wide-field fluorescein angiography. In some cases, optical coherence tomography angiography (OCT-A) serves as a non-invasive alternative to FA. Herein, we used OCT-A to examine the macular microvasculature in patients with VHL disease. SUBJECTS: Subjects were selected from patients with a diagnosis of VHL. The control group included eyes without retinal diagnosis from patients with an episode of unilateral retinal detachment or trauma and age ≤ 50 years old. METHODS: Subjects were scanned on the Optovue RTVue-XR device to acquire 3mm x 3mm OCT-A images of the superficial (SCP) and deep capillary plexus (DCP). SCP and DCP vessel density (VD) were calculated after the images were binarized. Furthermore, for subjects with RCH, each OCT-A image was divided equally into four quadrants. SCP and DCP VD of quadrants with RCH were compared to those without RCH. T-tests were performed for statistical analysis. RESULTS: 67 eyes with a history of VHL disease were included as study subjects, while 16 eyes were included as controls. Significant increases in VD were found in patients with VHL disease for both the SCP (p = 0.0441) and DCP (p = 0.0344). When comparing quadrants with associated RCH development to those without, we found no significant difference in SCP VD (p = 0.160) or DCP VD (p = 0.484). CONCLUSIONS: OCT-A can detect changes in the retinal microvasculature in the macula of patients with VHL disease. OCT-A imaging may be an additional tool for screening and early detection of patients at risk of developing ocular complications of VHL disease. Future studies should explore subtle progression on OCT-A associated with the pathogenesis and development of RCH, particularly with larger scan patterns.
Lu ES, Yuan A, Cohen DA, Katz R, Miller JB, Gaier ED. Detection of Choroidal Hypoperfusion in Giant Cell Arteritis Using Swept-Source Optical Coherence Tomographic Angiography. J Neuroophthalmol 2023;43(4):e117-e119.
Ludwig CA, Moon J, Garg I, Miller JB. Ultra-Widefield Imaging for Evaluation of the Myopic Eye. Semin Ophthalmol 2021;36(4):185-190.Abstract
Topic : Ultra-widefield (UWF) imaging of the myopic eye. Clinical Relevance : Myopes, and particularly high and pathologic myopes, present a unique challenge in fundoscopic imaging. Critical pathology is often located in the anteriormost portion of the retina, variations in posterior segment contour are difficult to capture in two-dimensional images, and extremes in axial length make simply focusing imaging devices difficult. Methods: We review the evolution of modalities for ophthalmic imaging (color fundus photography [CFP], optical coherence topography [OCT], angiography, artificial intelligence [AI]) to present day UWF technology and its impact on our understanding of myopia. Results: Advances in UWF technology address many of the challenges in fundoscopic imaging of myopes, providing new insights into the structure and function of the myopic eye. UWF CFP improves our ability to detect and document anterior peripheral pathology prevalent in approximately half of all high myopes. UWF OCT better captures the staphylomatous contour of the myopic eye, providing enhanced visualization of the vitreoretinal interface and progressive development of myopic traction maculopathy. UWF angiography highlights the posterior vortex veins, thin choriocapillaris, far peripheral avascularity, and peripheral retinal capillary microaneurysms more prevalent in the myopic eye. Researchers have demonstrated the ability of AI algorithms to predict refractive error, and great potential remains in the use of AI technology for the screening and prevention of myopic disease. Conclusion: We note significant progress in our ability to capture anterior pathology and improved image quality of the posterior segment of high and pathologic myopes. The next jump forward for UWF imaging will be the ability to capture a high quality ora to ora multimodal fundoscopic image in a single scan that will allow for sensitive AI-assisted screening of myopic disease.
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Milman T, Kao AA, Chu D, Gorski M, Steiner A, Simon CZ, Shih C, Aldave AJ, Eagle RC, Jakobiec FA, Udell I. Paraproteinemic Keratopathy: The Expanding Diversity of Clinical and Pathologic Manifestations. Ophthalmology 2015;122(9):1748-56.Abstract

PURPOSE: To describe 7 patients with paraproteinemic keratopathy and to highlight the clinical and pathologic diversity of this rare entity and the importance of timely, systemic evaluation. DESIGN: Retrospective, multicenter collaborative case series. PARTICIPANTS: Seven patients with paraproteinemic keratopathy. METHODS: Clinical and pathologic records were reviewed to identify patients with well-documented corneal immunoglobulin deposits. Detailed ophthalmologic and medical histories were assembled. In 6 patients, corneal tissue was evaluated histochemically and immunohistochemically; in selected cases, corneal tissue was evaluated by in situ hybridization and ultrastructurally. MAIN OUTCOME MEASURES: Visual acuity and anterior segment examination at presentation and follow-up; local therapy; systemic diagnosis and management; and histopathologic, immunohistochemical, in situ hybridization, and ultrastructural findings. RESULTS: Seven patients were identified with corneal immunoglobulin deposition. In addition to previously reported crystalline, nummular, patch-like, and lattice-like corneal opacities, prominent corneal vascularization was present in 2 patients mimicking interstitial keratitis and limbal stem cell deficiency. All patients had evidence of paraproteinemia in a setting of monoclonal gammopathy of undetermined significance, smoldering plasma cell myeloma, or Waldenström macroglobulinemia. Corneal findings were the first manifestation of systemic disease in 4 patients, and the diagnosis was not suspected in 3 of these patients. Pathologic evaluation of biopsied corneal and conjunctival tissues demonstrated immunoglobulin deposits. Previously unreported ultrastructural patterns in the cornea were noted: large scroll-like immunotactoid deposits, immune complex-like deposits, and randomly arranged fibrils morphologically intermediate between amyloid and immunotactoid deposits. Surgical intervention to improve vision was performed in 4 patients, with recurrence of deposits in 3 patients. Three patients underwent systemic therapy with diminution of the deposits and improvement in vision in 1 patient. CONCLUSIONS: The clinical and pathologic expressions of corneal immunoglobulin deposits are protean and present a diagnostic challenge. Early recognition of this rare entity is important to address the potentially serious associated systemic disease.

Moon JY, Garg I, Cui Y, Katz R, Zhu Y, Le R, Lu Y, Lu ES, Ludwig CA, Elze T, Wu DM, Eliott D, Miller JW, Kim LA, Husain D, Vavvas DG, Miller JB. Wide-field swept-source optical coherence tomography angiography in the assessment of retinal microvasculature and choroidal thickness in patients with myopia. Br J Ophthalmol 2023;107(1):102-108.Abstract
BACKGROUND/AIMS: Pathological myopia (PM) is a leading cause of blindness worldwide. We aimed to evaluate microvascular and chorioretinal changes in different stages of myopia with wide-field (WF) swept-source (SS) optical coherence tomography angiography (OCTA). METHODS: This prospective cross-sectional observational study included 186 eyes of 122 patients who had undergone imaging between November 2018 and October 2020. Vessel density (VD) and vessel skeletonised density (VSD) of superficial capillary plexus, deep capillary plexus and whole retina, as well as foveal avascular zone parameters, retinal thickness (RT) and choroidal thickness (CT), were calculated. RESULTS: This study evaluated 75 eyes of 48 patients with high myopia (HM), 43 eyes of 31 patients with mild to moderate myopia and 68 eyes of 53 age-matched controls. Controlling for age and the presence of systemic hypertension, we found that HM was associated with decrease in VD and VSD in all layers on 12×12 mm² scans. Furthermore, HM was associated with a VD and VSD decrease in every Early Treatment Diabetic Retinopathy Study grid, with a larger decrease temporally (βVD=-0.39, βVSD=-10.25, p<0.01). HM was associated with decreased RT and CT. Reduction in RT was outside the macular region, while reduction in CT was in the macular region. CONCLUSION: Using WF SS-OCTA, we identified reduction in microvasculature and structural changes associated with myopia. Decrease in VD and VSD was greater in the temporal quadrant, and reductions in RT and CT were uneven across the retina. Further work may help identify risk factors for the progression of PM and associated vision-threatening complications.
Moon JY, Wai KM, Patel NS, Katz R, Dahrouj M, Miller JB. Visualization of retinal breaks on ultra-widefield fundus imaging using a digital green filter. Graefes Arch Clin Exp Ophthalmol 2023;261(4):935-940.Abstract
PURPOSE: We compare the ability of resident physicians to identify retinal breaks on ultra-widefield color fundus photos using the traditional image compared to an image with a green filter overlay. METHODS: Residents were shown fundus photos of 10 eyes with either a retinal tear or hole. Participants were shown each photo twice-once with traditional color settings and once with a green filter overlay. Participants were scored on whether the break was correctly identified and timed on how long it took to identify the pathology. RESULTS: Residents were able to correctly identify more retinal breaks on fundus photos with a green filter overlay compared to photos with traditional settings (P = 0.02). Residents were also able to identify breaks on fundus photos more quickly on images with a green filter overlay compared to the traditional images (P < 0.001). CONCLUSIONS: The application of a green filter overlay may help in identifying retinal breaks.
Mujat M, Akula JD, Fulton AB, Ferguson DR, Iftimia N. Non-Rigid Registration for High-Resolution Retinal Imaging. Diagnostics (Basel) 2023;13(13)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.
Munsell MK, Garg I, Duich M, Zeng R, Baldwin G, Wescott HE, Koch T, Wang KL, Patel NA, Miller JB. A normative database of wide-field swept-source optical coherence tomography angiography quantitative metrics in a large cohort of healthy adults. Graefes Arch Clin Exp Ophthalmol 2023;Abstract
PURPOSE: Data from healthy eyes is needed to interpret optical coherence tomography angiography (OCTA) findings. However, very little normative data is available for wide-field swept-source OCTA (WF SS-OCTA), particularly 12 × 12-mm and disc-centered angiograms. Therefore, we aim to report quantitative metrics in a large sample of control eyes. METHODS: In this cross-sectional observational study, 482 eyes of 375 healthy adults were imaged on the 100 kHz Zeiss PLEX® Elite 9000 using protocols centered on the fovea (3 × 3, 6 × 6, and 12 × 12-mm) and optic disc (6 × 6 and 12 × 12-mm) between December 2018 and January 2022. The ARI Network (Zeiss Portal v5.4) was used to calculate vessel density (VD) and vessel skeletonized density (VSD) in the superficial capillary plexus, deep capillary plexus, and whole retina, as well as foveal avascular zone (FAZ) parameters. Mixed-effect multiple linear regression models were used for statistical analysis. RESULTS: The subjects' median age was 55 (38-63) years, and 201 (53.6%) were female. Greater age and worse best-corrected visual acuity (BCVA) were associated with significantly lower VD and VSD (p < 0.05). VD and VSD differed based on race and cataract status, but not sex, on some scan protocols (p < 0.05). FAZ circularity decreased with age, and FAZ dimensions differed based on race and ethnicity in certain scan protocols. CONCLUSIONS: We report a large database of parafoveal and peripapillary vascular metrics in several angiogram sizes. In referencing these values, researchers must consider characteristics such as age, race, and BCVA, but will have a valuable point of comparison for OCTA measurements in pathologic settings.
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Naninck T, Kahlaoui N, Lemaitre J, Maisonnasse P, De Mori A, Pascal Q, Contreras V, Marlin R, Relouzat F, Delache B, Hérate C, Aldon Y, van Gils M, Zabaleta N, Tsong Fang RH, Bosquet N, Sanders RW, Vandenberghe LH, Chapon C, Le Grand R. Computed tomography and [18F]-FDG PET imaging provide additional readouts for COVID-19 pathogenesis and therapies evaluation in non-human primates. iScience 2022;25(4):104101.Abstract
Non-human primates (NHPs) are particularly relevant as preclinical models for SARS-CoV-2 infection and nuclear imaging may represent a valuable tool for monitoring infection in this species. We investigated the benefit of computed X-ray tomography (CT) and [18F]-FDG positron emission tomography (PET) to monitor the early phase of the disease in a large cohort (n = 76) of SARS-CoV-2 infected macaques. Following infection, animals showed mild COVID-19 symptoms including typical lung lesions. CT scores at the acute phase reflect the heterogeneity of lung burden following infection. Moreover, [18F]-FDG PET revealed that FDG uptake was significantly higher in the lungs, nasal cavities, lung-draining lymph nodes, and spleen of NHPs by 5 days postinfection compared to pre-infection levels, indicating early local inflammation. The comparison of CT and PET data from previous COVID-19 treatments or vaccines we tested in NHP, to this large cohort of untreated animals demonstrated the value of in vivo imaging in preclinical trials.
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O'Bryhim BE, Lin JB, Van Stavern GP, Apte RS. OCT Angiography Findings in Preclinical Alzheimer's Disease: 3-Year Follow-Up. Ophthalmology 2021;128(10):1489-1491.
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Parikh R, Sakurada Y, Yannuzzi LA. Multimodal Imaging to Monitor Recurrent Serpiginous Choroiditis. Ophthalmology 2018;125(8):1252.

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