Hemodynamic and morphological changes of the central retinal artery in myopic eyes

The Role of Optical Coherence Tomography Angiography in Glaucoma

Glaucoma is the leading cause of irreversible vision loss and comprises a group of chronic optic neuropathies characterized by progressive retinal ganglion cell (RGC) loss. Various etiologies, including impaired blood supply to the optic nerve, have been implicated for glaucoma pathogenesis. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality for visualizing the ophthalmic microvasculature. Using blood flow as an intrinsic contrast agent, it distinguishes blood vessels from the surrounding tissue. Vessel density (VD) is mainly used as a metric for quantifying the ophthalmic microvasculature. The key anatomic regions for OCTA in glaucoma are the optic nerve head area including the peripapillary region, and the macular region. Specifically, VD of the superficial peripapillary and superficial macular microvasculature is reduced in glaucoma patients compared to unaffected subjects, and VD correlates with functional deficits measured by visual field (VF). This renders OCTA similar in diagnostic capabilities compared to structural retinal nerve fiber layer (RNFL) thickness measurements, especially in early glaucoma. Furthermore, in cases where RNFL thickness measurements are limited due to artifact or floor effect, OCTA technology can be used to evaluate and monitor glaucoma, such as in eyes with high myopia and eyes with advanced glaucoma. However, the clinical utility of OCTA in glaucoma management is limited due to the prevalence of imaging artifacts. Overall, OCTA can play a complementary role in structural OCT imaging and VF testing to aid in the diagnosis and monitoring of glaucoma.

The association of global vessel width with cognitive decline and cerebral small vessel disease burden in the KaiLuan study

Background

As the retinal microvasculature shares similarities with the cerebral microvasculature, numerous studies have shown that retinal vascular is associated with cognitive decline. In addition, several population-based studies have confirmed the association between retinal vascular and cerebral small vessel disease (CSVD) burden. However, the association of retinal vascular with CSVD burden as well as cognitive function has not been explored simultaneously. This study investigated the relations of retinal microvascular parameters (RMPs) with CSVD burden and cognitive function.

Methods

We conducted a cross-sectional study of participants in the KaiLuan study. Data were collected from subjects aged ≥18 years old who could complete retinal photography and brain magnetic resonance imaging (MRI) between December 2020 to October 2021 in the Kailuan community of Tangshan. RMPs were evaluated using a deep learning system. The cognitive function was measured using the Montreal Cognitive Assessment (MoCA). We conducted logistic regression models, and mediation analysis to evaluate the associations of RMPs with CSVD burden and cognitive decline.

Results

Of the 905 subjects (mean age: 55.42±12.02 years, 54.5% female), 488 (53.9%) were classified with cognitive decline. The fractal dimension (FD) [odds ratio (OR), 0.098, 95% confidence interval (CI): 0.015-0.639, P=0.015] and global vein width (OR: 1.010, 95% CI: 1.005-1.015, P<0.001) were independent risk factors for cognitive decline after adjustment for potential confounding factors. The global artery width was significantly associated with severe CSVD burden (OR: 0.985, 95% CI: 0.974-0.997, P=0.013). The global vein width was sightly associated with severe CSVD burden (OR: 1.005, 95% CI: 1.000-1.010, P=0.050) after adjusting for potential confounders. The multivariable-adjusted odds ratios (95% CI) in highest tertile versus lowest tertile of global vein width were 1.290 (0.901-1.847) for cognitive decline and 1.546 (1.004-2.290) for severe CSVD burden, respectively. Moreover, CSVD burden played a partial mediating role in the association between global vein width and cognitive function (mediating effect 6.59%).

Conclusions

RMPs are associated with cognitive decline and the development of CSVD. A proportion of the association between global vein width and cognitive decline may be attributed to the presence of CSVD burden.

Artificial intelligence and hemodynamic studies in optical coherence tomography angiography for diabetic retinopathy evaluation: A review

Diabetic retinopathy (DR) is a rapidly emerging retinal abnormality worldwide, which can cause significant vision loss by disrupting the vascular structure in the retina. Recently, optical coherence tomography angiography (OCTA) has emerged as an effective imaging tool for diagnosing and monitoring DR. OCTA produces high-quality 3-dimensional images and provides deeper visualization of retinal vessel capillaries and plexuses. The clinical relevance of OCTA in detecting, classifying, and planning therapeutic procedures for DR patients has been highlighted in various studies. Quantitative indicators obtained from OCTA, such as blood vessel segmentation of the retina, foveal avascular zone (FAZ) extraction, retinal blood vessel density, blood velocity, flow rate, capillary vessel pressure, and retinal oxygen extraction, have been identified as crucial hemodynamic features for screening DR using computer-aided systems in artificial intelligence (AI). AI has the potential to assist physicians and ophthalmologists in developing new treatment options. In this review, we explore how OCTA has impacted the future of DR screening and early diagnosis. It also focuses on how analysis methods have evolved over time in clinical trials. The future of OCTA imaging and its continued use in AI-assisted analysis is promising and will undoubtedly enhance the clinical management of DR.

Retinal Vascular Oxygen Saturation in a Sample of Chinese Myopic Adults

Purpose

The aim of the study was to investigate the normal retinal vascular oxygen saturation and to elucidate the factors affecting it or associated with it in a Chinese population.

Methods

This was a population-based observational cross-sectional study. Chinese myopic adults aged 18 to 45 years old were enrolled. Spherical equivalent (SE) and ocular biometry, including average keratometry (K), central corneal thickness, intraocular pressure, and axial length, were measured. The retinal arteriolar (SaO2) and venous (SvO2) oxygen saturation were measured after pupil dilatation.

Results

A total of 1373 participants were enrolled, and the mean age, SE, SaO2, and SvO2, were 26.31 ± 6.93 years, -6.40 ± 3.12 D, 93.47% ± 1.58%, and 63.08% ± 4.46%, respectively. In the multivariate analysis, SaO2, SvO2, and retinal arteriovenous oxygen saturation difference (AVD) were significantly correlated with age (β = 0.077, P = 0.006 for SaO2 and β = 0.080, P = 0.006 for AVD) and SE (β = 0.220, P < 0.001 for SaO2; β = 0.131, P < 0.001 for SvO2; and β = -0.050, P = 0.048 for AVD, respectively). Higher SaO2 was associated with larger K values (β = 0.094, P = 0.001).

Conclusions

SaO2 increased with older age, lower myopia, and larger K values, older age was associated with higher SaO2 and AVD, and SvO2 decreased with the deepening of myopia. Our present study provided normative values for healthy Chinese myopic adults with different myopic refractive errors.

Retinal Vascular Oxygen Saturation in Adults With Anisometropia

Purpose

This study aimed to examine the differences of retinal oxygen saturation between the paired eyes in anisometropia and to further explore the relation between retinal oxygenation and myopia.

Methods

This was an observational cross-sectional study, with 124 adults with anisometropia included. According to the interocular differences in spherical equivalent (SE), individuals with a difference ≥3.0 D belonged to the ΔSE ≥ 3.0 D group, and those with a difference ≥1.5 D and <3.0 D belonged to the ΔSE <3.0 D group. The ΔSE ≥ 3.0 D group contained 61, and the ΔSE < 3.0 D group contained 64. All were performed examinations of retinal oximetry, SE, axial length (AL), intraocular pressure, central corneal thickness and average keratometry.

Results

The median SE and AL were -5.06 (-7.22 ∼ -3.41) D and 25.54 (24.73 ∼ 26.62) mm in the "ΔSE < 3 D" group and -4.25 (-6.88 ∼ -2.09) D and 25.52 (24.49 ∼ 26.45) mm in the other group. The retinal arterial oxygen saturation (SaO2) was 93.97% ± 1.26% in the less myopic eyes and 93.18% ± 1.53% (P < 0.001) in the more myopic eyes. In multivariate analyses, SE and AL were both significantly associated with the SaO2.

Conclusions

The SaO2 between anisometropic myopic eyes was different, and it was associated with SE and AL.

Translational Relevance

This study demonstrates a relationship between myopia and retinal vascular oxygenation through a novel retinal oximeter.