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Retinal Changes
Published in Giuseppe Mancia, Guido Grassi, Konstantinos P. Tsioufis, Anna F. Dominiczak, Enrico Agabiti Rosei, Manual of Hypertension of the European Society of Hypertension, 2019
Optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in an enhanced resolution within an acceptable time period. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging (47). In addition to its diagnostic use in various ophthalmologic diseases, OCT has emerged as tool to assess structural compounds involved in neurodegeneration that contribute to neurologic disability in a variety of central nervous system diseases (48). Currently, as a clinical tool, OCT is particularly useful for the structural measurement of peripapillary retinal nerve fibre layer thickness, optic nerve head volumetric analysis and macular anatomy (49). Schuster et al. proposed OCT-based retinal vessel analysis for the evaluation of hypertensive vasculopathy (50). They demonstrated a relationship between blood pressure and OCT-based arterial-venous ratio (11). However, data about the retinal vessel parameters in arterial hypertension are limited. In an analysis of patients aged over 50 years, it was shown that mean arteriolar outer and inner diameter did not differ between patients with (n = 103) and without hypertension (n = 83) but mean arterial wall thickness was significantly larger (51). This is in line with previous findings using SLDF in never-treated hypertensive patients compared to controls (23). In addition, in patients with poor blood pressure control (BP ≥140/90 mmHg), calculation of OCT-measured WLR (0.396 ± 0.16) was similar to those measured using SLDF (37,51), but no direct comparison has thus far been made. In addition, retinal microvascular damage assessed with OCT in patients with obstructive sleep apnoea (OSAS) and hypertension was associated with OSAS severity (52).
Effect of ECG-gating Retinal Photographs on Retinal Vessel Caliber Measurements in Subjects with and without Type 2 Diabetes
Published in Current Eye Research, 2021
Anchal Lal, Neha Dave, Oliver J. Gibbs, Michael Anthony (Tony) Barry, Annika Sood, Paul Mitchell, Aravinda Thiagalingam
However, a higher coefficient of variation in retinal arterioles than veins remained despite ECG-gating, and could be partially explained by spontaneous oscillations which are higher in retinal arterioles than venules.15 These oscillations normally diminish at an unknown short distance from the optic disc edge.15,23 We did not take this into account when selecting our slice section for retinal vessel analysis. However, the widely reported standardised approach that we used in selecting slice sections was at some distance from the optic disc margin, suggesting that spontaneous oscillations may not majorly influence retinal caliber measurements. The retinal arteriolar coefficient of variation also remained higher in type 2 diabetes than controls despite ECG-gating, implying that factors other than pulsatility may still affect the accuracy of retinal vessel caliber measurements. Spontaneous oscillations are also less likely to explain this finding as they are significantly reduced in type 2 diabetes with retinopathy compared to controls, attributed to impaired autoregulation and increased retinal vascular stiffness.23 Kumar et al.24 detected pulsatile properties, in addition to cardiac cycle-induced, that occur in single vessel segments along many retinal arterioles and venules. While this study was done with healthy controls only, it raises the importance of identifying non-pulsatile segments prior to performing retinal vessel analysis, which was not considered in this study and could have influenced our results.
Effect of Pupil Dilation with Tropicamide on Retinal Vascular Caliber
Published in Ophthalmic Epidemiology, 2019
Shaun Frost, Cynthia Gregory, Liam Robinson, Shuang Yu, Di Xiao, Maryam Mehdizadeh, Samantha Burnham, Cirous Dehghani, Janardhan Vignarajan, Yogesan Kanagasingam, Markus P. Schlaich, David Prentice
Retinal photographs were analyzed with CSIRO semi-automated software; a cloud based intelligent retinal Vessel AnalysiS Platform (VASP, Australian Patent Office 2018902107).20 The measured retinal zones of interest for the vessel width measurements were 0.5–1.0 disc diameters away from the disc margin (zone B, Figure 1) or 1.0–2.0 disc diameters away from the disc margin (zone C, Figure 1). Measurement in these zones ensured that the vessels had become arteriolar. Trained graders followed a standardized protocol and performed corrections to automated procedures as necessary. Vascular calibers were calculated for the six largest arterioles and six largest venules. Summary measures of vascular equivalent caliber were also calculated (central retinal arterial (CRAE) and venular (CRVE) equivalent caliber), based on the improved Knudston–Parr–Hubbard formula.21,22 CRAE and CRVE represent the equivalent single-vessel parent calibre for the six arterioles and venules respectively. The optic nerve head was used for scale conversion from pixels to microns (µm), with semi-automatic and grader adjusted optic disc segmentation and assumed diameter of 1800 µm, as per the standard approach used by other software. Additionally, a fully computerized optic nerve head segmentation and diameter calculation was applied, using a local phase symmetry algorithm23 with region growing. The region growing algorithm is used to locate the boundary of the optic disc with the maximum phase symmetry response as a seed. The minimal diameter enclosing the optic disc boundary is the detected disc diameter.
Comparing Common Retinal Vessel Caliber Measurement Software with an Automatic Deep Learning System
Published in Current Eye Research, 2023
Shuang He, Gabriella Bulloch, Liangxin Zhang, Wei Meng, Danli Shi, Mingguang He
This study aimed to compare the performance of RMHAS and IVAN for automated retinal vessel analysis in a large-scale Chinese cohort. The ICC results indicated good agreement between the two software programs. However, further analysis revealed the presence of proportional bias and significant mean differences between measurements for CRAE and CRVE. In addition, some systemic variables showed significant but weak correlations with retinal vessel calibers. To address these issues, a conversion algorithm was developed to improve the interchangeability and eliminate the large mean differences between measurements.