Ophthalmic imaging of ocular circulation for detecting disease

Harris, Alon; Primus, Sally; Siesky, Brent; Zore, Matt; Tobe, Leslie

doi:10.1533/9780857097477.2.163

Cited by 3 publications

(4 citation statements)

References 108 publications

(103 reference statements)

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“…LDF measures a Doppler shift caused by the flow of red blood cells to determine blood flow at the optic nerve head ( 55 ). However, LDF has limited small vessel resolution ( 6 ) and tissue depth ( 58 ), issues with data interpretation across studies ( 58 , 59 ), and variable reproducibility ( 6 , 60 ). OCT, on the other hand, has become the standard for structural ocular imaging due to its ability to directly obtain noninvasive images with a spatial resolution of 4 μm and scanning depth of 500 μm ( 11 ).…”

Section: Discussionmentioning

confidence: 99%

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

Baker

Safarzadeh

Incognito

et al. 2022

Journal of Applied Physiology

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Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. Additionally, while sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow. We evaluated the retinal microvasculature in males (n=11) and females (n=7) using functional optical coherence tomography at baseline (1,130m) (Day 0), following rapid ascent (Day 2) and prolonged exposure (Day 9) to high altitude (3,800m). Retinal vascular perfusion density (rVPD; an index of total blood supply), retinal thickness (RT; reflecting vascular and neural tissue volume) and arterial blood were acquired. As a group, rVPD increased on Day 2 vs. Day 0 (p<0.001) and was inversely related to PaO2 (R2=0.45; p=0.006). By Day 9, rVPD recovered to baseline, but was significantly lower in males vs. females (p=0.007). RT was not different on Day 2 vs. Day 0 (p>0.99) but was reduced by Day 9 relative to Day 0 and Day 2 (p<0.001). RT changes relative to Day 0 were inversely related to changes in PaO2 on Day 2 (R2=0.6; p=0.001) and Day 9 (R2=0.4; p=0.02). RT did not differ between sexes. These data suggest differential time course and regulation of the retina during rapid ascent and prolonged exposure to high altitude and are the first to demonstrate sex-specific differences in rVPD at high altitude. The ability to assess intact microvasculature contiguous with the brain has widespread research and clinical applications.

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Section: Discussionmentioning

confidence: 99%

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

Baker

Safarzadeh

Incognito

et al. 2022

Journal of Applied Physiology

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“…Diagnostic performance varies considerably between studies illnesses with slightly better results when assessing the OA. Even though alterations of ocular blood flow could be used as a valuable tool in diagnosing ocular pathologies their acquisition remains a technical challenge and a no gold standard for assessment exists due to inherent limitations of the available techniques [4, 20]. Another problem in daily business is the lack of standardized methods in CDI assessment as Stalmans et al already indicated [21].…”

Section: Discussionmentioning

confidence: 99%

“…Compared to fluorescein angiography (FA), CDI allows for assessing the ocular blood flow in a non-invasive manner. Numerous studies have examined changes in ocular blood flow velocities in various diseases affecting the eye such as carotid artery and retinal vein occlusion, diabetic retinopathy (DRP) and glaucoma, and have revealed significant differences compared to healthy subjects even in early stages of disease (reviewed in [3, 4]). As an example, Evans and colleagues [5] demonstrated that diabetic patients with minimal or no retinopathy demonstrate irregular flow levels in the major vessels feeding the eye.…”

Section: Introductionmentioning

confidence: 99%

Colour Doppler analysis of ophthalmic vessels in the diagnosis of carotic artery and retinal vein occlusion, diabetic retinopathy and glaucoma: systematic review of test accuracy studies

et al. 2016

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BackgroundColour Doppler analysis of ophthalmic vessels has been proposed as a promising tool in the diagnosis of various eye diseases, but the available diagnostic evidence has not yet been assessed systematically. We performed a comprehensive systematic review of the literature on the diagnostic properties of Colour Doppler imaging (CDI) assessing ophthalmic vessels and provide an inventory of the available evidence.MethodsEligible papers were searched electronically in (Pre) Medline, Embase and Scopus, and via cross-checking of reference lists. The minimum requirement to be included was the availability of original data and the possibility to construct a two-by-two table. Study selection, critical appraisal using the QUADAS II instrument and extraction of salient study characteristics was made in duplicate. Sensitivity and specificity was computed for each study.ResultsWe included 11 studies (15 two-by-two tables) of moderate methodological quality enrolling 820 participants (range 30 to 118). In 44.4% participants were female (range 37–59% in specific subgroups). CDI was assessed for internal carotid stenosis, diabetic retinopathy, glaucoma, and branch or central retinal vein occlusion diagnosis. There was insufficient data to pool the results for specific illnesses. For the assessments of ophthalmic arteries, mean sensitivity was 0.69 (range 0.27–0.96) with a corresponding mean specificity of 0.83 (range 0.70–0.96). Mean sensitivity of the central retinal artery assessments was 0.58 (range 0.31–0.84) and the corresponding mean specificity was 0.82 (range 0.63–0.94).ConclusionsRobust assessments of the diagnostic value of colour Doppler analysis remain uncommon, limiting the possibilities to extrapolate its true potential for clinical practice.PROSPERO 2014:CRD42014014027.

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“…Decreased clearance via aqueous veins is characteristic of POAG, 34 and decreased choroidal flow is observed in wet AMD. 35 Elimination mechanism deactivation was a starting point for modeling POAG and wet AMD by simulating extreme cases. Afterward, varying disease severity was simulated by reducing the flow rate of blood through the choroid (subdomain 6) by 50% to 99% of its initial value to examine the relationship between choroidal blood flow and drug transport.…”

Section: Methodsmentioning

confidence: 99%

Modeling the Effects of Disease, Drug Properties, and Material on Drug Transport From Intraocular Lenses

Clasky

Meunier

Wells

2022

Trans. Vis. Sci. Tech.

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Purpose Surgically implanted intraocular lenses (IOLs) may be used as drug-delivery devices, but their effectiveness is not well defined. Computational fluid dynamics models were developed to investigate the capability of IOLs to release drugs at therapeutic concentrations. Methods Models were generated using COMSOL Multiphysics. Primary open-angle glaucoma (POAG) and wet age-related macular degeneration (AMD) were simulated by reducing aqueous vein and choroidal blood flow, respectively. Release of dexamethasone, ganciclovir, or dextran was studied using common IOL materials, polydimethylsiloxane (PDMS) and poly(2-hydroxyethyl methacrylate) (PHEMA). Results Drug clearance proceeds mainly through choroidal blood flow. When fully constricted, maximum concentration at the choroid ( C max ) values increased by 32.4% to 39,800%. Compared to dexamethasone, C max in different tissues decreased by 6.07% to 96.0% for ganciclovir and dextran, and clearance rates decreased by 16% to 69% for ganciclovir and by 92% to 100% for dextran. Using PDMS as the IOL reduced clearance rates by 91.3% to 94.6% compared to PHEMA. Conclusions In diseased eyes, drugs accumulate mainly in posterior tissue; thus, choroidal drug toxicity must be assessed prior to IOL implantation in POAG and AMD patients. Moreover, drug properties modulated concentration profiles in all ocular segments. The hydrophobic small-molecule dexamethasone attained the highest concentrations and cleared the fastest, whereas hydrophilic macromolecular dextran attained the lowest concentrations and cleared the slowest. Furthermore, high concentrations were achieved quickly following release from PHEMA, whereas PDMS allowed for sustained release. Translational Relevance In silico results can guide scientists and clinicians regarding important physiological and chemical factors that modulate tissue drug concentrations from drug-eluting IOLs.

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Ophthalmic imaging of ocular circulation for detecting disease

Cited by 3 publications

References 108 publications

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

Colour Doppler analysis of ophthalmic vessels in the diagnosis of carotic artery and retinal vein occlusion, diabetic retinopathy and glaucoma: systematic review of test accuracy studies

Modeling the Effects of Disease, Drug Properties, and Material on Drug Transport From Intraocular Lenses

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