Impairment of autoregulation of optic nerve head blood flow during vitreous surgery in patients with hypertension and hyperlipidemia

Colorimetric Analyses of the Optic Nerve Head and Retina Indicate Increased Blood Flow After Vitrectomy

Purpose

The purpose of this study was to evaluate the impact of vitrectomy and posterior hyaloid (PH) peeling on color alteration of optic nerve head (ONH) and retina as a surrogate biomarker of induced perfusion changes.

Methods

Masked morphometric and colorimetric analyses were conducted on preoperative (<1 month) and postoperative (<18 months) color fundus photographs of 54 patients undergoing vitrectomy, either with (44) or without (10) PH peeling and 31 years of age and gender-matched control eyes. Images were calibrated according to the hue and saturation values of the parapapillary venous blood column. Chromatic spectra of the retinal pigment epithelium and choroid were subtracted to avoid color aberrations. Red, green, and blue (RGB) bit values over the ONH and retina were plotted within the constructed RGB color space to analyze vitrectomy-induced color shift. Vitrectomy-induced parapapillary vein caliber changes were also computed morphometrically.

Results

A significant post-vitrectomy red hue shift was noted on the ONH (37.1 degrees ± 10.9 degrees vs. 4.1 degrees ± 17.7 degrees, P < 0.001), which indicates a 2.8-fold increase in blood perfusion compared to control (2.6 ± 1.9 vs. 0.9 ± 1.8, P < 0.001). A significant post-vitrectomy increase in the retinal vein diameter was also noticed (6.8 ± 6.4% vs. 0.1 ± 0.3%, P < 0.001), which was more pronounced with PH peeling (7.9 ± 6.6% vs. 3.1 ± 4.2%, P = 0.002).

Conclusions

Vitrectomy and PH peeling increase ONH and retinal blood flow. Colorimetric and morphometric analyses offer valuable insights for future artificial intelligence and deep learning applications in this field.

Translational Relevance

The methodology described herein can easily be applied in different clinical settings and may enlighten the beneficial effects of vitrectomy in several retinal vascular diseases.

Methods to measure blood flow and vascular reactivity in the retina

Disturbances of retinal perfusion are involved in the onset and maintenance of several ocular diseases, including diabetic retinopathy, glaucoma, and retinal vascular occlusion. Hence, knowledge on ocular vascular anatomy and function is highly relevant for basic research studies and for clinical judgment and treatment. The retinal vasculature is composed of the superficial, intermediate, and deep vascular layer. Detection of changes in blood flow and vascular diameter especially in smaller vessels is essential to understand and to analyze vascular diseases. Several methods to evaluate blood flow regulation in the retina have been described so far, but no gold standard has been established. For highly reliable assessment of retinal blood flow, exact determination of vessel diameter is necessary. Several measurement methods have already been reported in humans. But for further analysis of retinal vascular diseases, studies in laboratory animals, including genetically modified mice, are important. As for mice, the small vessel size is challenging requiring devices with high optic resolution. In this review, we recapitulate different methods for retinal blood flow and vessel diameter measurement. Moreover, studies in humans and in experimental animals are described.

Intravitreal Dexamethasone Implant Has Better Retinal Perfusion than Anti-Vascular Endothelial Growth Factor Treatment for Macular Edema Secondary to Retinal Vein Occlusion: A Five-Year Real-World Study

PURPOSE

The purpose of the study was to investigate the long-term effect of intravitreal dexamethasone (DEX) implant and anti-vascular endothelial growth factor (VEGF) injection on macular edema (ME) secondary to retinal vein occlusion (RVO) in a real-world setting.

METHODS

The medical records of RVO-ME cases, with intravitreal injections and followed up for at least 5 years, were retrospectively reviewed. Changes in best-corrected visual acuity (BCVA) and central macular thickness (CMT) were primary outcomes. Images of fluorescence angiography and swept-source optical coherence tomography angiography were analyzed. Foveal avascular zone (FAZ) metrics and perfusion density at the last visit were also compared between the two treatments.

RESULTS

A total of 16 patients were recruited, 8 in the anti-VEGF group and 8 in the DEX group. At the 5th year, the BCVA and the CMT in the DEX group were not different from those in the anti-VEGF group (0.69 ± 0.36 LogMAR vs. 0.57 ± 0.30 LogMAR, p = 0.574; 183.25 ± 97.31 µm vs. 195.38 ± 40.92 µm, p = 0.442). Compared with the anti-VEGF group, the DEX group had higher FAZ circularity index (0.57 ± 0.14 vs. 0.68 ± 0.14, p = 0.130) and higher retinal perfusion density (0.45 ± 0.02 vs. 0.39 ± 0.03, p = 0.001), especially in the deep capillary plexus.

CONCLUSION

DEX implant and anti-VEGF injection had comparative long-term effects on RVO-ME. Compared with the anti-VEGF treatment, the DEX treatment had advantages in maintaining retinal perfusion in patients with RVO.

Chinese herbal medicine for hypertension complicated with hyperlipidemia: A protocol for a systematic review and meta-analysis

BACKGROUND

Hypertension combined with hyperlipidemia (HTN-HLP), as a common clinical chronic disease combination, will increase the incidence of cardiovascular and cerebrovascular diseases, increase the occurrence of sudden death and other adverse events. At present, the commonly used therapeutic drugs are mainly combined with antihypertensive drugs and lipid-lowering drugs, which not only have poor compliance, but also have adverse reactions. Currently, traditional Chinese medicine, as a traditional medicine in China, has been applied in clinical practice for thousands of years and has rich clinical experience in treating HTN-HLP. However, there is no systematic evaluation of the efficacy, safety and improvement of patients' quality of life. This systematic review and meta-analysis will assess studies of the effects and safety of Chinese herbal medicine (CHM) for HTN-HLP patients.

METHODS

We will search PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science (ISI), China National Knowledge Infrastructure, Wan fang Database, Chinese Scientific Journals Full-Text Database (VIP) and China Biological Medicine Database from the time when databases were established to 01, February 2021. After a series of screening, randomized controlled trials (RCTs) will be included related to CHM for HTN-HLP. Two researchers will assess the RCTs through the Cochrane bias risk assessment tool. And the evidence grade of the results will be evaluated by GRADEprofiler software.

RESULTS

This study will provide a reliable evidence for the efficiency of antihypertensive and reducing blood lipids of CHM for HTN-HLP.

CONCLUSION

We will summarize the methods and provide sufficient evidence to confirm the efficacy and safety of CHM for HTN-HLP.

INPLASY REGISTRATION NUMBER

INPLASY2020110144.

Longitudinal effects of common carotid artery stenosis on ocular hemodynamics assessed using laser speckle flowgraphy in a rabbit model

Real-time impairment of ocular blood flow (OBF) under common carotid artery stenosis (CCAS) has not been ascertained. We aimed to longitudinally assess the impact of CCAS on OBF using a rabbit model. About 75% stenosis was created by tying the common carotid artery with a plastic mandrel using a nylon suture. The plastic mandrel was gently removed, leaving a ligature. Neurological and behavioral assessments were recorded as the clinical indicator of stroke severity. With laser speckle flowgraphy, the pulse waveform parameters namely mean blur rate (MBR), blowout score (BOS), blowout time (BOT), rising rate, S1-area, falling rate (FR), S2-area, flow acceleration index (FAI), acceleration time index, resistive index (RI) and the difference between the maximum and minimum values of MBR (AC) were assessed in overall, vessel, and tissue regions of the optic nerve head (ONH). Longitudinally, BOS significantly increased until day 19 post-surgery, whereas FAI, RI, and AC significantly decreased. Beyond day 19, BOS, BOT, FR, FAI, RI, and AC significantly decreased. We defined two stages representing impaired vessel conditions, namely the vessel resistance phase, where BOS increases and FAI, RI, and AC decrease, and the vessel elasticity phase where BOS, BOT, FR, FAI, RI and AC decrease. These stages provide information about atherosclerosis, assessable non-invasively through the eye.

Time Course in Ocular Blood Flow and Pulse Waveform in a Case of Ocular Ischemic Syndrome with Intraocular Pressure Fluctuation

We report on a 70-year-old Japanese man with complaints of worsening left visual acuity who was diagnosed with ocular ischemic syndrome (OIS) associated with internal carotid artery (ICA) stenosis. A gonioscopy examination showed rubeosis iridis and elevated intraocular pressure (IOP) in the left eye (50 mmHg) at the baseline visit. The optic nerve head (ONH) and choroidal blood flow measured by laser speckle flowgraphy (LSFG) was impaired in the left eye compared with that in the right eye. Additionally, the blowout score (BOS), which indicates the variation of the mean blur rate (MBR) during systolic and diastolic periods, was decreased in the left eye. After treatment with an injection of bevacizumab and administration of Rho-associated kinase-inhibitor ripasudil eye drops, both ocular blood flow and BOS in each vascular bed gradually increased along with IOP reduction. The visual acuity also improved. The current case demonstrated increased blood flow and decreased fluctuation of blood flow in the ONH and choroid before and after the treatment in OIS with rubeosis iridis. The LSFG technique is useful to non-invasively assess the ocular circulation and pulse waveform in OIS.

Epiretinal Membrane Surgery in Daily Clinical Practice: Results of a Proposed Management Scheme

Purpose

To report the results of the epiretinal membrane (ERM) management guidelines followed in our center.

Methods

Patients with ERM seen between 2014 and 2015, with ≥2 years follow-up or who had undergone ERM surgery, were included. Corrected visual acuity (VA), lens status, and ERM configuration were recorded at each visit. Our guidelines for ERM are if VA is ≥20/30, observation is recommended unless there is moderate/intense metamorphopsia. Vitrectomy is recommended during follow-up if there is a drop >one line in VA with changes in ERM configuration. If VA at diagnosis is <20/30, vitrectomy is recommended. If visual loss is thought to be due to cataract, phacoemulsification is performed first and visual status reevaluated.

Results

Ninety-nine eyes of 94 patients were included; 52 eyes underwent vitrectomy, and 47 eyes were monitored. From eyes with VA at diagnosis <20/30 (41 eyes), 8 eyes underwent isolated phacoemulsification: VA improved to ≥20/30. Vitrectomy was recommended but refused by 4 patients. The other 29 eyes underwent vitrectomy. Of the 58 eyes with VA at diagnosis ≥20/30, 5 underwent surgery due to metamorphopsia. Eighteen eyes underwent vitrectomy during follow-up. VA improved a mean of 0.13 logMAR (SD 0.30) after vitrectomy. There were no differences in mean VA improvement between eyes that underwent vitrectomy within six months of diagnosis (0.24, SD 0.32) and those that underwent surgery more than six months after diagnosis (mean 0.17, SD 0.17), p=0.106. Three eyes developed postsurgical complications with visual loss: persistent macular edema in one eye, two consecutive retinal detachments in one eye, and a central visual defect in another eye. At the end of follow-up, VA was similar in the observation group (0.14, SD 0.14) and in the vitrectomy group (0.16, SD 0.28), p=0.528.

Conclusions

Our proposed guidelines lead to visual preservation in most patients while limiting surgery and its possible complications.

Evaluation of flicker induced hyperemia in the retina and optic nerve head measured by Laser Speckle Flowgraphy

Purpose

The coupling between neural activity and blood flow is a physiological key principle of ocular blood flow regulation. The current study was performed to investigate whether Laser speckle flowgraphy (LSFG), a commercially available technique for measuring blood flow, is capable to assess flicker-induced haemodynamic changes in the retinal and optic nerve head (ONH) circulation.

Methods

Twenty healthy subjects were included in this cross sectional study. A commercial LSFG instrument was used to measure blood flow at the ONH as well as in retinal vessels before and during stimulation with flickering light. Mean blur rate (MBR), a measure of relative blood flow velocity, was obtained for the ONH and relative flow volume (RFV) a measure of relative blood flow of the respective retinal vessels.

Results

Stimulation with flicker light increased ONH MBR by +17.5%±6.6% (p<0.01). In retinal arteries, flicker stimulation led an increase of +23.8±10.0% (p<0.05) in total RFV. For retinal veins, an increase of +23.1%±11.0 (p<0.05) in total RFV was observed during stimulation. A higher response was observed in nasal RFV compared to temporal RFV in retinal arteries (nasal: +28.9%±20.0%; temporal: +20.4%±17.6%, p<0.05) and veins (nasal: +28.3%±19.6%; temporal +17.8%±18.9%, p<0.05).

Conclusion

As shown previously with other techniques, flicker stimulation leads to an increase in retinal and optic nerve head blood flow. Our results indicate that LSFG is an appropriate method for the quantification of retinal and ONH blood flow during visual stimulation and may be used as a non-invasive, easy to use tool to assess neuro-vascular coupling in humans.

Comparison of Optic Nerve Head Blood Flow Autoregulation among Quadrants Induced by Decreased Ocular Perfusion Pressure during Vitrectomy

Purpose

The present study aimed to examine changes in optic nerve head (ONH) blood flow autoregulation in 4 quadrants (superior, nasal, inferior, and temporal) with decreased ocular perfusion pressure (OPP) during vitrectomy in order to determine whether there is a significant difference of autoregulatory capacity in response to OPP decrease at each ONH quadrant.

Methods

This study included 24 eyes with an epiretinal membrane or macular hole that underwent vitrectomy at Toho University Sakura Medical Center. Following vitrectomy, the tissue mean blur rate (MBR), which reflects ONH blood flow, was measured. Mean tissue MBRs in the four quadrants were generated automatically in the software analysis report. Measurements were conducted before and 5 and 10 min after intraocular pressure (IOP) elevation of approximately 15 mmHg in the subjects without systemic disorders.

Results

The baseline tissue MBR of the temporal quadrant was significantly lower than that of the other 3 quadrants (all P < 0.05). However, the time courses of tissue MBR in response to OPP decrease were not significantly different among the four quadrants during vitrectomy (P = 0.23).

Conclusions

There is no significant difference in the autoregulatory capacity of the four ONH quadrants in patients without systemic disorders during vitrectomy.