Vessel Diameter

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Mark E Olson - One of the best experts on this subject based on the ideXlab platform.

  • constant theoretical conductance via changes in Vessel Diameter and number with height growth in moringa oleifera
    Journal of Experimental Botany, 2019
    Co-Authors: Alberto Echeverria, Julieta A Rosell, Tommaso Anfodillo, Diana Soriano, Mark E Olson
    Abstract:

    As trees grow taller, hydraulic resistance can be expected to increase, causing photosynthetic productivity to decline. Yet leaves maintain productivity over vast height increases; this maintenance of productivity suggests that leaf-specific conductance remains constant as trees grow taller. Here we test the assumption of constant leaf-specific conductance with height growth and document the stem xylem anatomical adjustments involved. We measured the scaling of total leaf area, mean Vessel Diameter at terminal twigs and at the stem base, and total Vessel number in 139 individuals of Moringa oleifera of different heights, and estimated a whole-plant conductance index from these measurements. Whole-plant conductance and total leaf area scaled at the same rate with height. Congruently, whole-plant conductance and total leaf area scaled isometrically. Constant conductance is made possible by intricate adjustments in anatomy, with conduit Diameters in terminal twigs becoming wider, lowering per-Vessel resistance, with a concomitant decrease in Vessel number per unit leaf area with height growth. Selection maintaining constant conductance per unit leaf area with height growth (or at least minimizing drops in conductance) is likely a potent selective pressure shaping plant hydraulics, and crucially involved in the maintenance of photosynthetic productivity per leaf area across the terrestrial landscape.

  • Vessel Diameter is related to amount and spatial arrangement of axial parenchyma in woody angiosperms
    Plant Cell and Environment, 2018
    Co-Authors: Mark E Olson, Lenka Plavcova, Hugh Morris, Mark A F Gillingham, Sean M Gleason, David A Coomes, Esther Fichtler, Matthias Klepsch, Hugo I Martinezcabrera
    Abstract:

    Parenchyma represents a critically important living tissue in the sapwood of the secondary xylem of woody angiosperms. Considering various interactions between parenchyma and water transporting Vessels, we hypothesise a structure-function relationship between both cell types. Through a generalised additive mixed model approach based on 2,332 woody angiosperm species derived from the literature, we explored the relationship between the proportion and spatial distribution of ray and axial parenchyma and Vessel size, while controlling for maximum plant height and a range of climatic factors. When factoring in maximum plant height, we found that with increasing mean annual temperatures mean Vessel Diameter showed a positive correlation with axial parenchyma proportion and arrangement, but not for ray parenchyma. Species with a high axial parenchyma tissue fraction tend to have wide Vessels, with most of the parenchyma packed around Vessels, while species with small Diameter Vessels show a reduced amount of axial parenchyma that is not directly connected to Vessels. This finding provides evidence for independent functions of axial parenchyma and ray parenchyma in large Vesselled species and further supports a strong role for axial parenchyma in long distance xylem water transport.

  • scaling of xylem Vessel Diameter with plant size causes predictions and outstanding questions
    Current Forestry Reports, 2017
    Co-Authors: Julieta A Rosell, Mark E Olson, Tommaso Anfodillo
    Abstract:

    This review shows that a more or less constant rate of tip-to-base Vessel widening across species, together with the assumption that wider Vessels are more vulnerable to embolism, suggests how climate should limit maximum vegetation height; together, these two factors predict a maximum mean Vessel Diameter permitted by temperature and water availability at a site and thus maximum plant height. Empirical work makes it increasingly clear that the main driver of variation in mean Vessel Diameter is plant size, specifically the length of the conductive stream. Anatomical evidence, together with hydraulic optimality models, suggests that this Vessel Diameter-stem length relationship is the result of natural selection favoring the maintenance of constant hydraulic resistance over size increases. From their very narrow termini, Vessels widen predictably from the stem tip to the base, following approximately a power law, i.e., with very rapid widening toward the tips and nearly constant Diameter toward the base. This size dependence must be taken into account when studying the hydraulics-climate relationship. This review discusses outstanding predictions that require testing, including the following: variation in the Vessel Diameter-stem length relationship should involve factors such as Vessel length distributions, pit characteristics, leaf area, and wood density; leaves higher in trees should have higher terminal leaf vein-petiole base Vessel widening rates; species without “disposable” units (e.g., columnar cacti) might have different widening rates; and within-plant widening rate should vary as plants approach their height limits. Finally, we emphasize the need to standardize for size in making comparisons of Vessel Diameter variation.

  • universal hydraulics of the flowering plants Vessel Diameter scales with stem length across angiosperm lineages habits and climates
    Ecology Letters, 2014
    Co-Authors: Mark E Olson, Tommaso Anfodillo, Julieta A Rosell, Giai Petit, Alan Crivellaro, Sandrine Isnard, Calixto Leongomez, Leonardo O Alvaradocardenas, Matiss Castorena
    Abstract:

    Angiosperm hydraulic performance is crucially affected by the Diameters of Vessels, the water conducting conduits in the wood. Hydraulic optimality models suggest that Vessels should widen predictably from stem tip to base, buffering hydrodynamic resistance accruing as stems, and therefore conductive path, increase in length. Data from 257 species (609 samples) show that Vessels widen as predicted with distance from the stem apex across angiosperm orders, habits and habitats. Standardising for stem length, Vessels are only slightly wider in warm/moist climates and in lianas, showing that, rather than climate or habit, plant size is by far the main driver of global variation in mean Vessel Diameter. Terminal twig Vessels become wider as plant height increases, while Vessel density decreases slightly less than expected tip to base. These patterns lead to testable predictions regarding evolutionary strategies allowing plants to minimise carbon costs per unit leaf area even as height increases.

  • convergent Vessel Diameter stem Diameter scaling across five clades of new and old world eudicots from desert to rain forest
    International Journal of Plant Sciences, 2013
    Co-Authors: Mark E Olson, Julieta A Rosell, Leonardo O Alvaradocardenas, Calixto Leon, Salvador Zamora, Andrea Weeks, Ivalu N Cacho, Jason R Grant
    Abstract:

    Premise of research. Variation in average xylem Vessel Diameter across species has important functional consequences, but the causes of this variation remain unclear. Average Vessel Diameter is known to scale with stem size within and across species. Vessel Diameter also seems to differ between clades and across environments, with dryland plants having narrower, more cavitation-resistant Vessels. As a result, it is not clear to what extent phylogenetic affinity and environment are associated with differences in the Vessel Diameter–stem size relationship.Methodology. With linear models and correlations, we explored the influence of environment and phylogeny on the Vessel Diameter–stem Diameter relationship in a molecular phylogenetic context across 83 species in four families spanning desert to rain forest in the Americas, Africa, Asia, and Madagascar.Pivotal results. Mean species Vessel Diameter was strongly predicted by trunk Diameter (slope ∼0.33), and this slope was not affected by either phylogenetic ...

Julieta A Rosell - One of the best experts on this subject based on the ideXlab platform.

  • constant theoretical conductance via changes in Vessel Diameter and number with height growth in moringa oleifera
    Journal of Experimental Botany, 2019
    Co-Authors: Alberto Echeverria, Julieta A Rosell, Tommaso Anfodillo, Diana Soriano, Mark E Olson
    Abstract:

    As trees grow taller, hydraulic resistance can be expected to increase, causing photosynthetic productivity to decline. Yet leaves maintain productivity over vast height increases; this maintenance of productivity suggests that leaf-specific conductance remains constant as trees grow taller. Here we test the assumption of constant leaf-specific conductance with height growth and document the stem xylem anatomical adjustments involved. We measured the scaling of total leaf area, mean Vessel Diameter at terminal twigs and at the stem base, and total Vessel number in 139 individuals of Moringa oleifera of different heights, and estimated a whole-plant conductance index from these measurements. Whole-plant conductance and total leaf area scaled at the same rate with height. Congruently, whole-plant conductance and total leaf area scaled isometrically. Constant conductance is made possible by intricate adjustments in anatomy, with conduit Diameters in terminal twigs becoming wider, lowering per-Vessel resistance, with a concomitant decrease in Vessel number per unit leaf area with height growth. Selection maintaining constant conductance per unit leaf area with height growth (or at least minimizing drops in conductance) is likely a potent selective pressure shaping plant hydraulics, and crucially involved in the maintenance of photosynthetic productivity per leaf area across the terrestrial landscape.

  • scaling of xylem Vessel Diameter with plant size causes predictions and outstanding questions
    Current Forestry Reports, 2017
    Co-Authors: Julieta A Rosell, Mark E Olson, Tommaso Anfodillo
    Abstract:

    This review shows that a more or less constant rate of tip-to-base Vessel widening across species, together with the assumption that wider Vessels are more vulnerable to embolism, suggests how climate should limit maximum vegetation height; together, these two factors predict a maximum mean Vessel Diameter permitted by temperature and water availability at a site and thus maximum plant height. Empirical work makes it increasingly clear that the main driver of variation in mean Vessel Diameter is plant size, specifically the length of the conductive stream. Anatomical evidence, together with hydraulic optimality models, suggests that this Vessel Diameter-stem length relationship is the result of natural selection favoring the maintenance of constant hydraulic resistance over size increases. From their very narrow termini, Vessels widen predictably from the stem tip to the base, following approximately a power law, i.e., with very rapid widening toward the tips and nearly constant Diameter toward the base. This size dependence must be taken into account when studying the hydraulics-climate relationship. This review discusses outstanding predictions that require testing, including the following: variation in the Vessel Diameter-stem length relationship should involve factors such as Vessel length distributions, pit characteristics, leaf area, and wood density; leaves higher in trees should have higher terminal leaf vein-petiole base Vessel widening rates; species without “disposable” units (e.g., columnar cacti) might have different widening rates; and within-plant widening rate should vary as plants approach their height limits. Finally, we emphasize the need to standardize for size in making comparisons of Vessel Diameter variation.

  • universal hydraulics of the flowering plants Vessel Diameter scales with stem length across angiosperm lineages habits and climates
    Ecology Letters, 2014
    Co-Authors: Mark E Olson, Tommaso Anfodillo, Julieta A Rosell, Giai Petit, Alan Crivellaro, Sandrine Isnard, Calixto Leongomez, Leonardo O Alvaradocardenas, Matiss Castorena
    Abstract:

    Angiosperm hydraulic performance is crucially affected by the Diameters of Vessels, the water conducting conduits in the wood. Hydraulic optimality models suggest that Vessels should widen predictably from stem tip to base, buffering hydrodynamic resistance accruing as stems, and therefore conductive path, increase in length. Data from 257 species (609 samples) show that Vessels widen as predicted with distance from the stem apex across angiosperm orders, habits and habitats. Standardising for stem length, Vessels are only slightly wider in warm/moist climates and in lianas, showing that, rather than climate or habit, plant size is by far the main driver of global variation in mean Vessel Diameter. Terminal twig Vessels become wider as plant height increases, while Vessel density decreases slightly less than expected tip to base. These patterns lead to testable predictions regarding evolutionary strategies allowing plants to minimise carbon costs per unit leaf area even as height increases.

  • convergent Vessel Diameter stem Diameter scaling across five clades of new and old world eudicots from desert to rain forest
    International Journal of Plant Sciences, 2013
    Co-Authors: Mark E Olson, Julieta A Rosell, Leonardo O Alvaradocardenas, Calixto Leon, Salvador Zamora, Andrea Weeks, Ivalu N Cacho, Jason R Grant
    Abstract:

    Premise of research. Variation in average xylem Vessel Diameter across species has important functional consequences, but the causes of this variation remain unclear. Average Vessel Diameter is known to scale with stem size within and across species. Vessel Diameter also seems to differ between clades and across environments, with dryland plants having narrower, more cavitation-resistant Vessels. As a result, it is not clear to what extent phylogenetic affinity and environment are associated with differences in the Vessel Diameter–stem size relationship.Methodology. With linear models and correlations, we explored the influence of environment and phylogeny on the Vessel Diameter–stem Diameter relationship in a molecular phylogenetic context across 83 species in four families spanning desert to rain forest in the Americas, Africa, Asia, and Madagascar.Pivotal results. Mean species Vessel Diameter was strongly predicted by trunk Diameter (slope ∼0.33), and this slope was not affected by either phylogenetic ...

  • Vessel Diameter stem Diameter scaling across woody angiosperms and the ecological causes of xylem Vessel Diameter variation
    New Phytologist, 2013
    Co-Authors: Mark E Olson, Julieta A Rosell
    Abstract:

    Summary Variation in angiosperm Vessel Diameter is of major functional significance. In the light of recent models predicting optimal Vessel taper given resistance imposed by conductive path length, we tested the prediction that plant size should predict Vessel Diameter, with dryland plants having narrower Vessels for their stem sizes. We assembled a comparative dataset including Vessel and stem Diameter measurements from 237 species from over 40 angiosperm orders across a wide range of habits and habitats. Stem Diameter predicted Vessel Diameter across self-supporting plants (slope 0.36, 95% CI 0.32–0.39). Samples from 142 species from five communities of differing water availability showed no tendency for dryland plants to have narrower Vessels. Predictable relationships between Vessel Diameter and stem Diameter mirrored predictable relationships between stem length and Diameter across self-supporting species. That Vessels are proportional to stem Diameter and stem Diameter is proportional to stem length suggests that taper in relation to conductive path length gives rise to the Vessel Diameter–stem Diameter relationship. In turn, plant size is related to climate, leading indirectly to the Vessel–climate relationship: Vessels are likely narrower in drier communities because dryland plants are on average smaller, not because they have narrow Vessels for their stem sizes.

Patricia Parsonswingerter - One of the best experts on this subject based on the ideXlab platform.

  • selective inhibition of angiogenesis in small blood Vessels and decrease in Vessel Diameter throughout the vascular tree by triamcinolone acetonide
    Investigative Ophthalmology & Visual Science, 2008
    Co-Authors: Terri L Mckay, Mary B Vickerman, Daniela Ribita, Harry H Olar, Peter K Kaiser, Dan J Gedeon, Alan Hylton, Patricia Parsonswingerter
    Abstract:

    PURPOSE To quantify the effects of the steroid triamcinolone acetonide (TA) on branching morphology within the angiogenic microvascular tree of the chorioallantoic membrane (CAM) of quail embryos. METHODS Increasing concentrations of TA (0-16 ng/mL) were applied topically on embryonic day (E) 7 to the chorioallantoic membrane (CAM) of quail embryos cultured in petri dishes and incubated for an additional 24 or 48 hours until fixation. Binary (black/white) microscopic images of arterial end points were quantified by generational analysis of Vessel branching (VESGEN) software to obtain major vascular parameters that include Vessel Diameter (D(v)), fractal dimension (D(f)), tortuosity (T(v)), and densities of Vessel area, length, number, and branch point (A(v), L(v), N(v), and Br(v)). For assessment of specific changes in vascular morphology induced by TA, the VESGEN software automatically segmented the vascular tree into branching generations (G(1)... G(10)) according to changes in Vessel Diameter and branching. RESULTS Vessel density decreased significantly up to 34% as the function of increasing concentration of TA according to A(v), L(v), Br(v), N(v), and D(f). TA selectively inhibited the growth of new, small Vessels because L(v) decreased from 13.14 +/- 0.61 cm/cm(2) for controls to 8.012 +/- 0.82 cm/cm(2) at 16 ng TA/mL in smaller branching generations (G(7)-G(10)) and for N(v) from 473.83 +/- 29.85 cm(-2) to 302.32 +/- 33.09 cm(-2). In contrast, Vessel Diameter (D(v)) decreased throughout the vascular tree (G(1)-G(10)). CONCLUSIONS By VESGEN analysis, TA selectively inhibited the angiogenesis of smaller blood Vessels, but decreased the Vessel Diameter of all Vessels within the vascular tree.

  • triamcinolone acetonide selectively inhibits angiogenesis in small blood Vessels and decreases Vessel Diameter within the vascular tree
    2007
    Co-Authors: Terri L Mckay, Dan J Gredeon, Mary B Vickerman, Alan G Hylton, Daniela Ribita, Harry H Olar, Peter K Kaiser, Patricia Parsonswingerter
    Abstract:

    The steroid triamcinolone acetonide (TA) is a potent anti-angiogenesis drug used to treat retinal vascular diseases that include diabetic retinopathy, vascular occlusions and choroidal neovascularization. To quantify the effects of TA on branching morphology within the angiogenic microvascular tree of the chorioallantoic membrane (CAM) of quail embryos. Increasing concentrations of TA (0-16 ng/ml) were applied topically on embryonic day 7 (E7) to the chorioallantoic membrane (CAM) of quail embryos cultured in Petri dishes, and incubated for an additional 24 or 48 hours until fixation. Binary (black/white) microscopic images of arterial end points were quantified by VESGEN software (for Generational Analysis of Vessel Branching) to obtain major vascular parameters that include Vessel Diameter (Dv), fractal dimension (Df), tortuosity (Tv) and densities of Vessel area, length, number and branch point (Av, Lv, Nv and Brv). For assessment of specific changes in vascular morphology induced by TA, the VESGEN software automatically segmented the vascular tree into branching generations (G1...G10) according to changes in Vessel Diameter and branching. Vessel density decreased significantly up to 34% as the function of increasing concentration of TA according to Av, Lv, Brv, Nv and Df. TA selectively inhibited the growth of new, small Vessels, because Lv decreased from 13.14plus or minus 0.61 cm/cm2 for controls to 8.012 plus or minus 0.82 cm/cm2 at 16 ng TA/ml in smaller branching generations (G7-G10), and for Nv from 473.83 plus or minus 29.85 cm(-)2 to 302.32 plus or minus 33.09 cm-()2. In contrast, Vessel Diameter (Dv) decreased throughout the vascular tree (G1-G10).

  • a vegf165 induced phenotypic switch from increased Vessel density to increased Vessel Diameter and increased endothelial nos activity
    Microvascular Research, 2006
    Co-Authors: Patricia Parsonswingerter, Terri L Mckay, Unni M Chandrasekharan, Krishnan Radhakrishnan, Paul E Dicorleto, Brian Albarran, Andrew G Farr
    Abstract:

    Abstract Although vascular endothelial growth factor-165 (VEGF 165 ) regulates numerous angiogenic cellular activities, its complex effects on vascular morphology are not highly quantified. By fractal-based, multiparametric branching analysis of 2D vascular pattern in the quail chorioallantoic membrane (CAM), we report that Vessel density increased maximally at lower VEGF concentrations, but that Vessel Diameter and activity of endothelial nitric oxide synthase (eNOS) increased maximally at higher VEGF concentrations. Following exogenous application of human VEGF 165 to the CAM at embryonic day 7, Vessel density and Diameter were measured after 24 h at arterial end points by the fractal dimension ( D f ) and generational branching parameters for Vessel area density ( A v ), Vessel length density ( L v ) and Vessel Diameter ( D v ) using the computer code VESGEN. The VEGF-dependent phenotypic switch from normal Vessels displaying increased Vessel density to abnormal, dilated Vessels typical of tumor vasculature and other pathologies resulted from an approximate threefold increase in VEGF concentration (1.25 to 5 μg/CAM) and correlated positively with increased eNOS activity. Relative to control specimens, eNOS activity increased maximally to 60% following VEGF treatment at 5 μg/CAM, compared to 10% at 1.25 μg/CAM, and was accompanied by no significant change in activity of inducible NOS. In summary, VEGF 165 induced a phenotypic switch from increased Vessel density associated with low VEGF concentration, to increased Vessel Diameter and increased eNOS activity at high VEGF concentration.

Einar Stefansson - One of the best experts on this subject based on the ideXlab platform.

  • retinal Vessel oxygen saturation and Vessel Diameter in retinitis pigmentosa
    Acta Ophthalmologica, 2014
    Co-Authors: Thor Eysteinsson, Sveinn Hakon Hardarson, David Bragason, Einar Stefansson
    Abstract:

    Purpose To assess retinal Vessel oxygen saturation and retinal Vessel Diameter in retinitis pigmentosa. Methods A retinal oximeter (Oxymap ehf., Reykjavik, Iceland) was used to measure retinal Vessel oxygen saturation and Vessel Diameter in ten patients with retinitis pigmentosa (RP) (mean age 49 years, range 23–71 years). Results were compared with age- and gender-matched healthy individuals. All patients had advanced stage of the disease with visual fields restricted to the macular region. Results Oxygen saturation in retinal venules was 58.0 ± 6.2% in patients with RP and 53.4 ± 4.8% in healthy subjects (p = 0.017). Oxygen saturation in retinal arterioles was not significantly different between groups (p = 0.65). The mean Diameter of retinal arterioles was 8.9 ± 1.6 pixels in patients with RP and 11.4 ± 1.2 in healthy controls (p < 0.0001). The corresponding Diameters for venules were 10.1 ± 1.2 (RP) and 15.3 ± 1.7 (healthy, p < 0.0001). Conclusions Increased venous saturation and decreased retinal Vessel Diameter suggest decreased oxygen delivery from the retinal circulation in retinitis pigmentosa. This is probably secondary to tissue atrophy and reduced oxygen consumption.

  • reliability of Vessel Diameter measurements with a retinal oximeter
    Graefes Archive for Clinical and Experimental Ophthalmology, 2011
    Co-Authors: Renata Blondal, Margret Kara Sturludottir, Sveinn Hakon Hardarson, Gisli H Halldorsson, Einar Stefansson
    Abstract:

    Background The purpose of this study was to test the reliability of Vessel Diameter measurements with a newly developed retinal oximeter.

Qianying Gao - One of the best experts on this subject based on the ideXlab platform.

  • retinal Vessel oxygen saturation and Vessel Diameter in retinitis pigmentosa at various ages
    Graefes Archive for Clinical and Experimental Ophthalmology, 2016
    Co-Authors: Yao Zong, Leilei Lin, Xia Huang, Yanmin Dong, Xiaobing Qian, Qianying Gao
    Abstract:

    This study was conducted to determine whether oxygen saturation and retinal blood Vessel Diameter are affected by retinitis pigmentosa (RP) at various ages. Relative oxygen saturation was measured in retinal blood Vessels in 68 RP patients and 136 normal subjects using the Oxymap T1 retinal oximeter. Subjects were divided into two age groups: Group A (20–40 years) and Group B (> 40 years). One randomly selected eye of each subject was used for statistical analysis. Student's t tests were used to analyze the mean saturation and Diameter of retinal arterioles and venules and arteriovenous differences between RP and normal subjects in the two age groups. A Spearman test was used to analyze the correlation of mean saturation of retinal arterioles (AS) and arteriovenous differences (AVS) with visual acuity, disease duration, and electroretinogram (ERG) b-wave amplitude in patients with RP. AS was significantly higher in patients with RP (105.5 ± 9.4 %) than in normal subjects (94.5 ± 4.4 %, p = 0.000) in Group A, while in Group B, AS was significantly lower in RP patients (86.8 ± 10.3 %) than in healthy subjects (96.0 ± 4.8 %, p = 0.000). Vessel Diameter was smaller in RP patients than in normal subjects. AS and AVS showed a negative correlation with disease duration and a tendency toward positive correlation with ERG b-wave in patients with RP. The shifting characteristics of retinal Vessel oxygen saturation suggest that the pathological mechanism of retinal oxygen metabolic disorder differs by age in patients with RP.

  • retinal Vessel oxygen saturation and Vessel Diameter in high myopia
    Ophthalmic and Physiological Optics, 2015
    Co-Authors: Qishan Zheng, Yao Zong, Leilei Lin, Xia Huang, Wei Yang, Yongguang Yuan, Qianying Gao
    Abstract:

    Purpose To investigate changes in retinal Vessel oxygen saturation and Diameter in high myopia. Methods Relative oxygen saturation was measured in the retinal blood Vessels of 54 participants with high myopia and compared to a control group of 54 individuals with emmetropia with the Oxymap T1 retinal oximeter. The participants with high myopia were further divided into two groups according to the grade of myopic retinopathy: Group A (grade < M2) and Group B (grade ≥ M2). One-way anova was used to analyse the mean saturation and Diameter of retinal arterioles and venules and the mean difference in arterio-venous saturation among the four groups. Further analysis of multiple comparisons was performed with the Bonferroni test. Linear regression was used to analyse the correlation of ocular perfusion pressure or best corrected visual acuity with other variables. Results For all of the high myopia patients, retinal arteriole saturation (92.3 ± 5.6%) and the difference in arterio-venous saturation (30.8 ± 5.0%) were significantly lower than in normal individuals (96.0 ± 5.8%, 35.4 ± 6.2%; p = 0.006, p < 0.001, respectively). In Group A, only the difference in arterio-venous saturation (31.0 ± 4.7%) was significantly lower than in the control group (p = 0.011). In Group B, retinal arteriole saturation (92.2 ± 5.3%) and the difference in arterio-venous saturation (30.7 ± 5.3%) were also lower than the control group (p = 0.02, p = 0.001, respectively). Both retinal arteriole Diameter and retinal venule Diameter were narrower than in participants with high myopia than the control group (p < 0.001). No statistically significant correlations were found between ocular perfusion pressure or best corrected visual acuity with any other variables. Conclusions The study demonstrated decreased retinal arteriole saturation and decreased difference in arterio-venous saturation as well as narrowing retinal Vessel Diameter in highly myopic eyes. Further studies are needed to determine if such changes play a role in the development of high myopia and its complications or occur as a consequence of tissue remodelling during axial elongation.