Hypoxia challenge test and retinal circulation changes – a study using ocular coherence tomography angiography

Sousa, David Cordeiro; Leal, Inês; Moreira, Susana; Dionísio, Patrícia; Pinto, Luís Abegão; Marques-Neves, Carlos

doi:10.1111/aos.13622

Cited by 35 publications

(28 citation statements)

References 27 publications

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“…This increase in the number of microvessels detected on OCTA will result in a higher vessel density. 31 After this initial phase, continued inflammation and Aβ build-up may cause further damage resulting in a loss of (micro)vasculature in turn causing a decrease in vessel density, explaining why individuals suffering from full-blown AD may have lower vessel density. 16 17 32 In our cohort, no differences were found in FAZ size between Aβ+ and Aβ− individuals.…”

Section: Discussionmentioning

confidence: 99%

Optical coherence tomography angiography in preclinical Alzheimer’s disease

et al. 2019

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Background/aimsAs a protrusion from the brain, the retina might reflect the status of the brain. Previous studies showed a decrease in vessel density and foveal avascular zone (FAZ) enlargement on optical coherence tomography angiography (OCTA) in individuals suffering from Alzheimer’s disease (AD). This study aims to assess whether such changes are already present in preclinical stages of AD, in a population of monozygotic (MZ) twins.Methods124 cognitively healthy individuals (MZ twins, ages 60–93 years) underwent [18F]flutemetamol amyloid positron emission tomography (PET) scanning and OCTA. PET scans were visually rated for cortical amyloid-beta (Aβ) positivity. Parametric global cortical non-displaceable binding potential (BPND) was used as a continuous measure for Aβ aggregation. FAZ size and vessel densities for the inner and outer ring of the macular ETDRS grid and in a 3–6 mm ring around the optic nerve head (ONH) were measured.OCTA measures were associated with visual Aβ score, BPND and amyloid load estimated by twin concordance on visual Aβ score. Twin correlations were estimated as a measure of maximum heritability of OCTA measures.Results13 of 124 participants were Aβ+. Aβ+ individuals had significantly higher vessel density than Aβ– individuals in all regions but did not differ in FAZ size. Twin analyses showed a positive association between and vessel densities in all regions. BPND tended to be associated with higher vessel density in the inner ring. Twin correlations were moderate/high for all OCTA parameters except vessel density around the ONH, which correlated weakly.ConclusionRetinal vessel density was higher in individuals with preclinical AD.

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Section: Discussionmentioning

confidence: 99%

Optical coherence tomography angiography in preclinical Alzheimer’s disease

et al. 2019

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“…High‐altitude hypoxia could give rise to reduced arterial SpO 2 , consequently resulting in endothelial dysfunction of retinal vessels and well‐recognized hypoxia‐induced retinal vessels’ vasodilation (Sousa et al. ). As delivery of oxygen from the retinal circulation to retinal tissue can be estimated by the arteriovenous difference in saturation multiplied by blood flow, retinal and choroidal blood flow appears to be increased during hypoxia and this is in keeping with our result of the increase in retinal venous diameter and thickness of choroid tissue.…”

Section: Discussionmentioning

confidence: 99%

Retinal vessel oxygen saturation and vessel diameter in healthy individuals during high‐altitude exposure

Yang

Sun

et al. 2018

Acta Ophthalmologica

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Purpose: To assess changes of retinal vessel oxygen saturation and vessel diameter in healthy individuals during high-altitude exposure. Methods: Retinal oxygen saturation and vessel diameter were obtained at sea level (SL, 40 m) and high altitude (HA, 3681 m) on 17 healthy individuals from Beijing (six males, 28.06 AE 8.06 years) using Oxymap T1 and then compared with 21 residents from Yushu (10 males, 28.63 AE 6.00 years). Systemic and ocular parameters were also measured before and after high-altitude exposure. Data were presented as mean AE SD and analysed using paired and independent Student t-test with significance accepted at p < 0.05. Results: Short-term high-altitude exposure of Beijing Group significantly affected all the systemic and ocular parameters, as well as retinal oxygen saturation and vessel diameter ranging from overall quadrant to different quadrants, other than retinal venous oxygen saturation and retinal arterial diameter. However, these changes were not evident in those permanently living at HA. Pearson's correlation analysis revealed correlations between retinal oxygen saturation and systemic and ocular parameters (all p < 0.05). The multivariate linear regression analysis indicated that retinal arterial oxygen saturation was significantly associated with arterial peripheral arterial oxygen saturation (SpO 2 ) and subfoveal choroidal thickness. Conclusion: Short-term exposure to HA induces retinal microcirculation disturbance and auto-regulatory response in healthy individuals, which is probably attributed to arterial SpO 2 and endothelial dysfunction under hypoxic conditions.

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“…This local autoregulatory adaptation contributes to keep a rather stable oxygen pressure in the inner retina until PaO 2 levels are as low as 40 mm Hg. [27][28][29][30][31] The following protocol has been described in detail in a previous publication. 21 Briefly, the HCT is a standard test 23 performed at sea level to create a normobaric hypoxic environment by reducing the FiO 2 and making it equivalent to that of a flight cabin.…”

Section: Study Protocolmentioning

confidence: 99%

Retinal Vascular Reactivity in Type 1 Diabetes Patients Without Retinopathy Using Optical Coherence Tomography Angiography

Sousa

Leal

Moreira

et al. 2020

Invest. Ophthalmol. Vis. Sci.

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We hypothesize that patients with type 1 diabetes (T1D) may have abnormal retinal vascular responses before diabetic retinopathy (DR) is clinically evident. Optical coherence tomography angiography (OCTA) was used to dynamically assess the retinal microvasculature of diabetic patients with no clinically visible retinopathy. METHODS. Controlled nonrandomized interventional study. The studied population included 48 eyes of 24 T1D patients and 24 demographically similar healthy volunteers. A commercial OCTA device (AngioVue) was used, and two tests were applied: (1) the hypoxia challenge test (HCT) and (2) the handgrip test to induce a vasodilatory or vasoconstrictive response, respectively. The HCT is a standardized test that creates a mild hypoxic environment equivalent to a flight cabin. The handgrip test (i.e., isometric exercise) induces a sympathetic autonomic response. Changes in the parafoveal superficial and deep capillary plexuses in both tests were compared in each group. Systemic cardiovascular responses were also comparatively evaluated. RESULTS. In the control cohort, the vessel density of the median parafoveal superficial and deep plexuses increased during hypoxia (F 1,23 = 15.69, P < 0.001 and F 1,23 = 16.26, P < 0.001, respectively). In the T1D group, this physiological response was not observed in either the superficial or the deep retinal plexuses. Isometric exercise elicited a significant decrease in vessel density in both superficial and deep plexuses in the control group (F 1,23 = 27.37, P < 0.0001 and F 1,23 = 27.90, P < 0.0001, respectively). In the T1D group, this response was noted only in the deep plexus (F 1,23 = 11.04, P < 0.01). CONCLUSIONS. Our work suggests there is an early impairment of the physiological retinal vascular response in patients with T1D without clinical diabetic retinopathy.

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Hypoxia challenge test and retinal circulation changes – a study using ocular coherence tomography angiography

Abstract: To our knowledge, there are no published data specifically addressing mild hypoxia conditions and retinal microvasculature changes, using OCT-A. This pilot study may pave way to better understand vascular responses in disease setting.

Cited by 35 publications

References 27 publications

Optical coherence tomography angiography in preclinical Alzheimer’s disease

Optical coherence tomography angiography in preclinical Alzheimer’s disease

Retinal vessel oxygen saturation and vessel diameter in healthy individuals during high‐altitude exposure

Retinal Vascular Reactivity in Type 1 Diabetes Patients Without Retinopathy Using Optical Coherence Tomography Angiography

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