Purpose: To investigate the retinal vascular network alterations in highly myopic eyes. Methods: Thirty-three highly myopic eyes from 21 subjects and 47 mildly myopic or emmetropic eyes from 24 healthy control subjects were enrolled. Optical coherence tomography angiography (OCTA) was used to image the superficial, deep, and whole retinal vascular plexuses at the macular region. Highly myopic eye images were analyzed after adjusting the ocular magnification using Bennett's formula. Fractal analysis (box counting method, D_box) representing vessel density was performed in different annular and quadrantile zones of both large vessels and microvessels. Correlations between the vascular density, axial length, and spherical equivalent refractive error were analyzed. Results: The average density (D_box) of the superficial retinal annular zone (0.6–2.5 mm) microvessels was 1.741 ± 0.018 in highly myopic eyes and was shown to be significantly lower than that of the controls (1.773 ± 0.010, P < 0.001). Individual annular zone (bandwidth of 0.16 mm) analysis of highly myopic eyes revealed a significant level of microvessel alteration in all zones compared with the same zones in control eyes (P < 0.001). Furthermore, in the highly myopic group, the microvessel density was significantly correlated with axial length elongation in all three layers (r = −0.38 to −0.48; P < 0.05). Conclusions: This study reveals retinal microvascular network alterations in highly myopic eyes, which correlates with axial length elongation. Fractal analysis of the microvasculature by OCTA images may help to characterize the underlying pathophysiological mechanisms involved in high myopia.

To review the clinical and research value of optical coherence tomography angiography (OCTA) in the field of neurology. Current literature involving OCTA were reviewed through PubMed using the search terms “optical coherence tomography angiography”, with “multiple sclerosis”, “Alzheimer’s disease”, “optic neuropathy”, or other closely-related terms. OCTA has been applied in research to advance our understanding of the pathobiology of neurological disorders. OCTA-derived blood flow and vessel density measures are altered in multiple sclerosis (MS), Alzheimer’s disease (AD), and various optic neuropathies (ON) in varying regions of the posterior segment vasculature of the eye. These emerging research findings support the occurrence of retinal vascular alterations across a host of neurological disorders and raise the possibility that vasculopathy can be clinically relevant since it contributes to the pathobiology of several neurological disorders. OCTA may be beneficial for neurological research. Additional investigations using OCTA in neurological disorders will help to further validate its clinical and research utilities in terms of characterizing the role of vasculopathy in neurological disorders.

Amyloid-β (Aβ) accumulations have been identified in the retina for neurodegeneration-associated disorders like Alzheimer’s disease (AD), glaucoma, and age-related macular degeneration (AMD). Elevated retinal Aβ levels were associated with progressive retinal neurodegeneration, elevated cerebral Aβ accumulation, and increased disease severity with a decline in cognition and vision. Retinal Aβ accumulation and its pathological effects were demonstrated to occur prior to irreversible neurodegeneration, which highlights its potential in early disease detection and intervention. Using the retina as a model of the brain, recent studies have focused on characterizing retinal Aβ to determine its applicability for population-based screening of AD, which warrants a further understanding of how Aβ manifests between these disorders. While current treatments directly targeting Aβ accumulations have had limited results, continued exploration of Aβ-associated pathological pathways may yield new therapeutic targets for preserving cognition and vision. Here, we provide a review on the role of retinal Aβ manifestations in these distinct neurodegeneration-associated disorders. We also discuss the recent applications of retinal Aβ for AD screening and current clinical trial outcomes for Aβ-associated treatment approaches. Lastly, we explore potential future therapeutic targets based on overlapping mechanisms of pathophysiology in AD, glaucoma, and AMD.

Purpose: This study determined (1) how many vessels (i.e., the vessel sampling) are needed to reliably characterize the bulbar conjunctival microvasculature and (2) if characteristic information can be obtained from the distribution histogram of the blood flow velocity and vessel diameter. Methods: Functional slitlamp biomicroscope was used to image hundreds of venules per subject. The bulbar conjunctiva in five healthy human subjects was imaged on six different locations in the temporal bulbar conjunctiva. The histograms of the diameter and velocity were plotted to examine whether the distribution was normal. Standard errors were calculated from the standard deviation and vessel sample size. The ratio of the standard error of the mean over the population mean was used to determine the sample size cutoff. The velocity was plotted as a function of the vessel diameter to display the distribution of the diameter and velocity. Results: The results showed that the sampling size was approximately 15 vessels, which generated a standard error equivalent to 15% of the population mean from the total vessel population. The distributions of the diameter and velocity were not only unimodal, but also somewhat positively skewed and not normal. The blood flow velocity was related to the vessel diameter (r=0.23, P<0.05). Conclusions: This was the first study to determine the sampling size of the vessels and the distribution histogram of the blood flow velocity and vessel diameter, which may lead to a better understanding of the human microvascular system of the bulbar conjunctiva.

Purpose: To review the clinical applications and diagnostic value of the retinal function imager (RFI), briefly compare RFI to other optical imaging devices, and to describe recent developments. Methods: The search words “Retinal Functional Imager,” “optical imaging,” “retina angiography,” “avascular zone,” “foveal avascular zone,” and other closely related terms were used in PubMed to review current literature involving the RFI. Results: The functions of the RFI were utilized in over 44 microvascular studies, which reported that the microvasculature may alter in velocity, morphology, and oximetry when affected by a number of ocular, neurological, or systemic diseases. Recently developed automatic algorithms for noninvasive angiography of large retinal regions, segmenting vessels, measuring blood flow, blood velocity, vessel diameter, and oximetry may enhance the clinical applications of the RFI. Conclusion: The RFI has been used to characterize the retinal microvasculature under various conditions of all prevalent retinal diseases in addition to some central nerve system (CNS) and systemic diseases. Applying the RFI in research and clinical settings should help earlier diagnosis, support disease prevention, and improve treatment management.

Purpose: This study was conducted to determine blood flow velocities and corresponding vessel diameters to characterize the response of the bulbar conjunctival microvasculature to contact lens wear. Methods: A functional slit-lamp biomicroscope (FSLB), an adapted traditional slitlamp, was used to image the temporal bulbar conjunctiva of 22 healthy subjects before and after 6 hr of contact lens wear. All of the measurable venules on the conjunctiva were processed to yield vessel diameters and blood flow velocities. Results: The average blood flow velocity increased from 0.51±0.20 to 0.65±0.22 mm/sec (P<0.001) after 6 hr of lens wear. The blood flow velocity distribution showed a velocity increase that correlated with the vessel diameter increase from the baseline (r=0.826, P<0.05). This pattern maintained a similar trend after 6 hr of lens wear (r=0.925, P<0.05), and increased velocities were found across all of the vessel diameter ranges (P<0.001). Conclusions: Blood flow velocity increases across all of the vessel diameter ranges in response to contact lens wear. Functional slitlamp biomicroscope is capable of characterizing the bulbar microvascular response to contact lens wear.