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Abstract PurposeTo review retinal vein occlusion (RVO) and its relationship with retinal oxygen saturation via automated retinal oximetry in eyes with RVO. MethodsA literature review was performed in PubMed and Medline until October 2021 utilizing specific keywords and cross‐matched reference lists. ResultsThis review found RVO to be associated with risk factors including age, hypertension, cardiovascular and metabolic conditions, male gender, and glaucoma. These may be attributed to a breakdown of regulatory processes in the retina. Retinal venous oxygen saturation (SvO2) and arteriovenous difference in eyes with central RVO have been found to be reduced and elevated, respectively. The literature indicates variable and contradictory findings in regard to branch RVO and retinal oxygenation. Additionally, ischaemic eyes have been found to have elevated retinal arterial oxygen saturation; however, the literature reports variable results regarding SvO2levels. Medications have been suggested to increase SvO2in RVO eyes, which may represent an important mechanism for disease management. Ranibizumab is currently the most studied drug for retinal oxygenation in RVO and has been suggested to increase SvO2in RVO eyes. In comparison, dexamethasone was found to decrease SvO2. ConclusionThe current literature on retinal oxygenation in ischaemic subtypes of RVO and in drug therapies is minimal, and further work is required to expand upon our understanding of how ischaemia and drugs influence retinal oxygenation and clinical outcomes.
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Potential measurement error from vessel reflex and multiple light paths in dual‐wavelength retinal oximetry
Abstract PurposeThis study aims to characterize the dependence of measured retinal arterial and venous saturation on vessel diameter and central reflex in retinal oximetry, with an ultimate goal of identifying potential causes and suggesting approaches to improve measurement accuracy. MethodsIn 10 subjects, oxygen saturation, vessel diameter and optical density are obtained using Oxymap Analyzer software without diameter correction. Diameter dependence of saturation is characterized using linear regression between measured values of saturation and diameter. Occurrences of negative values of vessel optical densities (ODs) associated with central vessel reflex are acquired from Oxymap Analyzer. A conceptual model is used to calculate the ratio of optical densities (ODRs) according to retinal reflectance properties and single and double‐pass light transmission across fixed path lengths. Model‐predicted values are compared with measured oximetry values at different vessel diameters. ResultsVenous saturation shows an inverse relationship with vessel diameter (D) across subjects, with a mean slope of −0.180 (SE = 0.022) %/μm (20 < D < 180 μm) and a more rapid saturation increase at small vessel diameters reaching to over 80%. Arterial saturation yields smaller positive and negative slopes in individual subjects, with an average of −0.007 (SE = 0.021) %/μm (20 < D < 200 μm) across all subjects. Measurements where vessel brightness exceeds that of the retinal background result in negative values of optical density, causing an artifactual increase in saturation. Optimization of model reflectance values produces a good fit of the conceptual model to measured ODRs. ConclusionMeasurement artefacts in retinal oximetry are caused by strong central vessel reflections, and apparent diameter sensitivity may result from single and double‐pass transmission in vessels. Improvement in correction for vessel diameter is indicated for arteries however further study is necessary for venous corrections.
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- Award ID(s):
- 1654019
- PAR ID:
- 10499641
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Acta Ophthalmologica
- Volume:
- 102
- Issue:
- 3
- ISSN:
- 1755-375X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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