The eye and the heart

Whole exome sequencing of extreme age-related macular degeneration phenotypes

PURPOSE

Demographic, environmental, and genetic risk factors for age-related macular degeneration (AMD) have been identified; however, a substantial portion of the variance in AMD disease risk and heritability remains unexplained. To identify AMD risk variants and generate hypotheses for future studies, we performed whole exome sequencing for 75 individuals whose phenotype was not well predicted by their genotype at known risk loci. We hypothesized that these phenotypically extreme individuals were more likely to carry rare risk or protective variants with large effect sizes.

METHODS

A genetic risk score was calculated in a case-control set of 864 individuals (467 AMD cases, 397 controls) based on 19 common (≥1% minor allele frequency, MAF) single nucleotide variants previously associated with the risk of advanced AMD in a large meta-analysis of advanced cases and controls. We then selected for sequencing 39 cases with bilateral choroidal neovascularization with the lowest genetic risk scores to detect risk variants and 36 unaffected controls with the highest genetic risk score to detect protective variants. After minimizing the influence of 19 common genetic risk loci on case-control status, we targeted single variants of large effect and the aggregate effect of weaker variants within genes and pathways. Single variant tests were conducted on all variants, while gene-based and pathway analyses were conducted on three subsets of data: 1) rare (≤1% MAF in the European population) stop, splice, or damaging missense variants, 2) all rare variants, and 3) all variants. All analyses controlled for the effects of age and sex.

RESULTS

No variant, gene, or pathway outside regions known to be associated with risk for advanced AMD reached genome-wide significance. However, we identified several variants with substantial differences in allele frequency between cases and controls with strong additive effects on affection status after controlling for age and sex. Protective effects trending toward significance were detected at two loci identified in single-variant analyses: an intronic variant in FBLN7 (the gene encoding fibulin 7) and at three variants near pyridoxal (pyridoxine, vitamin B6) kinase (PDXK). Aggregate rare-variant analyses suggested evidence for association at ASRGL1, a gene previously linked to photoreceptor cell death, and at BSDC1. In known AMD loci we also identified 29 novel or rare damaging missense or stop/splice variants in our sample of cases and controls.

CONCLUSIONS

Identified variants and genes may highlight regions important in the pathogenesis of AMD and are key targets for replication.

The relationship of systemic markers of renal function and vascular function with retinal blood vessel responses

PURPOSE

To test the hypothesis of a significant relationship between systemic markers of renal and vascular function (processes linked to cardiovascular disease and its development) and retinal microvascular function in diabetes and/or cardiovascular disease.

METHODS

Ocular microcirculatory function was measured in 116 patients with diabetes and/or cardiovascular disease using static and continuous retinal vessel responses to three cycles of flickering light. Endothelial function was evaluated by von Willebrand factor (vWf), endothelial microparticles and soluble E selectin, renal function by serum creatinine, creatinine clearance and estimated glomerular filtration rate (eGFR). HbA1c was used as a control index.

RESULTS

Central retinal vein equivalence and venous maximum dilation to flicker were linked to HbA1c (both p < 0.05). Arterial reaction time was linked to serum creatinine (p = 0.036) and eGFR (p = 0.039); venous reaction time was linked to creatinine clearance (p = 0.018). Creatinine clearance and eGFR were linked to arterial maximum dilatation (p < 0.001 and p = 0.003, respectively) and the dilatation amplitude (p = 0.038 and p = 0.048, respectively) responses in the third flicker cycle. Of venous responses to the first flicker cycle, HbA1c was linked to the maximum dilation response (p = 0.004) and dilatation amplitude (p = 0.017), vWf was linked to the maximum constriction response (p = 0.016), and creatinine clearance to the baseline diameter fluctuation (p = 0.029). In the second flicker cycle, dilatation amplitude was linked to serum creatinine (p = 0.022).

CONCLUSIONS

Several retinal blood vessel responses to flickering light are linked to glycaemia and renal function, but only one index is linked to endothelial function. Renal function must be considered when interpreting retinal vessel responses.

Long Noncoding RNA-GAS5: A Novel Regulator of Hypertension-Induced Vascular Remodeling

Vascular remodeling is an important pathological feature of hypertension, leading to increased vascular resistance and reduced compliance. Endothelial cell (EC) and vascular smooth muscle cell (VSMC) dysfunction is involved in vascular remodeling. Long noncoding RNAs are potential regulators of EC and VSMC function. Herein, we determined whether long noncoding RNA-growth arrest-specific 5 (GAS5) is involved in hypertension-related vascular remodeling. We revealed that GAS5 knockdown aggravated hypertension-induced microvascular dysfunction as shown by increased retinal neovascularization and capillary leakage. GAS5 regulated the remodeling of arteries, including caudal arteries, carotid arteries, renal arteries, and thoracic arteries. GAS5 was mainly expressed in ECs and VSMCs, and its expression was significantly downregulated in hypertension. GAS5 knockdown affected endothelial activation, endothelial proliferation, VSMC phenotypic conversion, and EC-VSMC communication in vivo and in vitro. Mechanistically, GAS5 regulated EC and VSMC function through β-catenin signaling. This study identified GAS5 as a critical regulator in hypertension and demonstrated the potential of gene therapy and drug development for treating hypertension.

Multiple sclerosis and primary vascular dysregulation (Flammer syndrome)

Background

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS of still unknown aetiology. Flammer syndrome (FS) encompasses a set of symptoms and signs that are primarily but not solely related to the dysregulation of blood vessels. The purpose of the present study was to determine whether FS symptoms occur more often in MS patients than in controls.

Methods

Fifty-eight MS patients and 259 controls answered a questionnaire covering 15 symptoms and signs of FS.

Results

Six of the 15 symptoms and signs of FS (dizziness, low body mass index, cold hands and/or feet, tendency toward perfectionism, reduced thirst, feeling cold) were found significantly more often in MS patients than in controls. Seven additional symptoms and signs (tinnitus, headaches, increased pain sensation, long sleep-onset time, migraines, increased response to certain drugs, low blood pressure) also occurred more often in MS patients, but the difference in frequency was not statistically significant. One sign (reversible skin blotches) was found less often in MS patients, but the difference in frequency was not statistically significant. One symptom (increased smell perception) was found significantly less often in MS patients.

Conclusions

MS patients suffer significantly more often from FS symptoms and signs than controls. The reason for this association between MS and FS and the potential implications of this association still need to be determined.

Retinal vessel calibres and haemostasis in black and white South Africans: the SABPA study

OBJECTIVES

Retinal arteriolar narrowing associates with hypertension development and indicates increased cardiovascular risk. Evidence on whether the retinal vessel calibres are related to the haemostatic system is limited, especially in the black hypertension-prone population with a high stroke incidence. We therefore investigated the relationships between haemostatic markers and retinal vessel calibres.

METHODS

We performed a cross-sectional study involving 170 black (mean age, 58 years; 44% women) and 189 white (mean age, 49 years; 52% women) teachers, and determined ambulatory blood pressure, haemostatic factors (fibrinogen, von Willebrand factor, D-dimer, plasminogen activator inhibitor-1 and clot lysis time) and retinal vessel calibres (central retinal artery and vein equivalent). The black and white groups were stratified by median split of the retinal arteriolar calibre.

RESULTS

Both ethnic groups with a smaller arteriolar calibre had higher SBP and narrower venular calibres. In the black population, the central retinal vein equivalent was positively (β = 0.293; P = 0.024) associated with fibrinogen, whereas in the white population, the central retinal artery equivalent (β = -0.256; P = 0.016) was negatively and central retinal vein equivalent (β = 0.234; P = 0.021) positively associated with von Willebrand factor. Furthermore, clot lysis time was negatively associated with the central retinal artery equivalent (β = -0.390; P = 0.014) in the black group and positively associated with the central retinal vein equivalent (β = 0.275; P = 0.008) in the white group.

CONCLUSION

Relationships between markers of haemostasis and the retinal vessel calibres exist, and vary between ethnicities. Haemostatic alterations are linked to early retinal microvascular changes, and future studies should investigate whether it translates into an elevated stroke risk.

Role of long non-coding RNA-RNCR3 in atherosclerosis-related vascular dysfunction

Atherosclerosis is one of the most common vascular disorders. Endothelial cell (EC) dysfunction and vascular smooth muscle cell (VSMC) proliferation contributes to the development of atherosclerosis. Long non-coding RNAs (lncRNAs) have been implicated in several biological processes and human diseases. Here we show that lncRNA-RNCR3 is expressed in ECs and VSMCs. RNCR3 expression is significantly upregulated in mouse and human aortic atherosclerotic lesions, and cultured ECs and VSMCs upon ox-LDL treatment in vitro. RNCR3 knockdown accelerates the development of atherosclerosis, aggravates hypercholesterolemia and inflammatory factor releases, and decreases EC and VSMC proliferation in vivo. RNCR3 knockdown also reduces the proliferation and migration, and accelerates apoptosis development of EC and VSMC in vitro. RNCR3 acts as a ceRNA, and forms a feedback loop with Kruppel-like factor 2 and miR-185-5p to regulate cell function. This study reveals that RNCR3 has an atheroprotective role in atherosclerosis, and its intervention is a promising strategy for treating atherosclerosis-related vascular dysfunction.

Retinopathy is associated with impaired myocardial function assessed by advanced echocardiography in type 1 diabetes patients - The Thousand & 1 Study

AIMS

Retinopathy and heart disease in Type 1 Diabetes Mellitus (Type 1 DM) may be associated; however previous results have been conflicting. Tissue Doppler Imaging (TDI) and speckle-tracking echocardiography (STE) quantify myocardial function not assessable by conventional echocardiography. We investigated the association between severity of retinopathy and early myocardial dysfunction using conventional echocardiography, TDI and STE in Type 1 DM patients.

METHODS

Type 1 Diabetes Mellitus patients without known heart disease were included from the Steno Diabetes Center. The cross sectional association between retinopathy and myocardial function was analyzed in uni-and multivariable models. Retinopathy was categorized as nil-, simplex- or proliferative retinopathy.

RESULTS

A total of 1090 Type 1 Diabetes Mellitus patients were included, mean age was 49.6years and 53% were males. Left ventricular ejection fraction did not differ between groups of retinopathy. Global longitudinal strain (GLS) by STE decreased significantly with increasing degrees of retinopathy (nil; -18.6%, simplex; -18.2% (p=0.024), proliferative; -17.7% (p<0.001)), however differences attenuated in multivariable models (p⩾0.05). In univariable models, myocardial tissue velocities differed in relation to retinopathy: s' (nil; 6.9, simplex; 6.5, proliferative; 5.9 (p=0.001), e' (nil; 10.4, simplex; 9.2, proliferative; 7.9, p<0.001), a' (nil; 6.1, simplex; 6.7, proliferative; 7.0, p<0.001) and E/e' (nil; 6.7, simplex; 7.5, proliferative; 9.5, p<0.001). In multivariable models, differences persisted between nil and proliferative retinopathy for s', e' and E/e'.

CONCLUSION

Proliferative retinopathy is independently associated with decreased myocardial function assessed by Tissue Doppler Imaging in patients with Type 1 Diabetes Mellitus without history of heart disease.

Assessment of the retinal nerve fiber layer in individuals with obstructive sleep apnea

Background

The effect of obstructive sleep apnea (OSA) syndrome in the peripapillary retinal nerve fiber layer (RNFL) thicknesses remains unclear. The purpose of this study was to assess RNFL measurements acquired using scanning laser polarimetry (SLP) and optical coherence tomography (OCT) in patients with OSA.

Methods

The sample of this cross-sectional study included 40 OSA patients and 45 age-matched controls, consecutively and prospectively selected. All participants underwent at least one reliable standard automated perimetry (SAP) test, while RNFL measurements were obtained using the SLP and OCT. The OSA group was divided into 3 sub-groups based on the apnea/hypopnea index (AHI): mild, moderate, or severe OSA. SAP, SLP, and OCT outcomes were compared between the control and OSA groups. The relationship between AHI and RNFL parameters was also evaluated.

Results

Age was not different between both groups. Mean deviation of SAP was −0.47 ± 0.9 dB and −1.43 ± 2.3 dB in the control and OSA groups, respectively (p = 0.01). RNFL thickness measured with OCT was similar between groups. OSA patients showed increased nerve fiber indicator (NFI; 20.9 ± 7.9 versus 16.42 ± 7.82; p = 0.01) and decreased superior average (59.74 ± 10.35 versus 63.73 ± 6.58; p = 0.03) obtained with SLP compared with healthy individuals. In the total sample, NFI and AHI were moderately correlated (r = 0.358; p = 0.001). In severe OSA subjects (n = 22), NFI and AHI had a Spearman correlation coefficient of 0.44 (p = 0.04).

Conclusion

RNFL thickness measured with OCT did not differ significantly between groups. Severe OSA was related to a reduction of the RNFL thickness assessed by SLP.

Glaucoma-inducing Procedure in an In Vivo Rat Model and Whole-mount Retina Preparation

Glaucoma is a disease of the central nervous system affecting retinal ganglion cells (RGCs). RGC axons making up the optic nerve carry visual input to the brain for visual perception. Damage to RGCs and their axons leads to vision loss and/or blindness. Although the specific cause of glaucoma is unknown, the primary risk factor for the disease is an elevated intraocular pressure. Glaucoma-inducing procedures in animal models are a valuable tool to researchers studying the mechanism of RGC death. Such information can lead to the development of effective neuroprotective treatments that could aid in the prevention of vision loss. The protocol in this paper describes a method of inducing glaucoma - like conditions in an in vivo rat model where 50 µl of 2 M hypertonic saline is injected into the episcleral venous plexus. Blanching of the vessels indicates successful injection. This procedure causes loss of RGCs to simulate glaucoma. One month following injection, animals are sacrificed and eyes are removed. Next, the cornea, lens, and vitreous are removed to make an eyecup. The retina is then peeled from the back of the eye and pinned onto sylgard dishes using cactus needles. At this point, neurons in the retina can be stained for analysis. Results from this lab show that approximately 25% of RGCs are lost within one month of the procedure when compared to internal controls. This procedure allows for quantitative analysis of retinal ganglion cell death in an in vivo rat glaucoma model.

The waveform index of the ophthalmic artery predicts impaired coronary flow reserve

BACKGROUND

Coronary flow reserve (CFR) can decrease with impairment in coronary microcirculation, even in the absence of epicardial conduit obstruction. Recently, the ophthalmic artery (OA), which is the first major branch of the internal carotid artery and is representative of microarterioles, has been identified using color Doppler sonography. However, the features of ultrasound waveform indices suggestive of impaired OA microcirculation and the relationships between these indices and CFR have not been elucidated. The present study aimed to assess the features of ultrasound waveform indices suggestive of impaired OA microcirculation and the relationships between these indices and CFR.

METHODS AND RESULTS

A total of 30 consecutive patients with a normal coronary angiogram and normal left ventricular function were studied. Patients with ≥ 25% stenosis of the right common or internal carotid artery were excluded. The CFR was defined as the ratio of adenosine-induced hyperemic to baseline blood flow velocity with an intracoronary Doppler guidewire. Color Doppler imaging was used to determine the blood flow velocity of the right OA, and the indices of peripheral resistance (resistance index [RI], pulsatility index [PI], and systolic mean velocity to diastolic mean velocity [Sm/Dm] ratio) were calculated. The ultrasound form showed a distinctive biphasic wave during systole followed by a monophasic wave during diastole. The velocity component in the early-systolic wave was higher than that in the mid-systolic wave or the diastolic wave (31.4 ± 5.1 vs. 26.1 ± 5.4 vs. 15.9 ± 4.0 cm/s, P<0.0001). The RI and PI were not related to the CFR, and the Sm/Dm ratio was negatively correlated with the CFR (β=-0.415, P=0.022). However, the relationship was attenuated by clinical variables closely associated with the Sm/Dm ratio or CFR, and hemoglobin A1c was a common mediator. The best Sm/Dm ratio cutoff for predicting an impaired CFR was 2.5 based on a receiver operating characteristic curve analysis.

CONCLUSIONS

An increase in the Sm/Dm ratio, which reflects a characteristic waveform, indicates impaired OA microcirculation. The ratio is negatively correlated with CFR, and therefore, it may be applied for the noninvasive evaluation of coronary physiology. Furthermore, hemoglobin A1c may be a common mediator for the OA and coronary microcirculation.

Retinal venous pressure: the role of endothelin

The retinal venous pressure (RVP) can be measured non-invasively. While RVP is equal to or slightly above intraocular pressure (IOP) in healthy people, it is often markedly increased in patients with eye or systemic diseases. Beside a mechanical obstruction, the main cause of such an elevation is a local dysregulation of a retinal vein, particularly a constriction induced by endothelin-1 (ET-1). A local increase of ET-1 can result from a high plasma level, as ET-1 can diffuse from the fenestrated capillaries of the choroid into the optic nerve head (ONH), bypassing the blood retinal barrier. A local increase can also result from increased local production either by a sick neighboring artery or retinal tissue. Generally, the main factors increasing ET-1 are inflammations and hypoxia, either locally or in a remote organ. RVP is known to be increased in patients with glaucoma, retinal vein occlusion (RVO), diabetic retinopathy, high mountain disease, and primary vascular dysregulation (PVD). PVD is the major vascular component of Flammer syndrome (FS). An increase of RVP decreases perfusion pressure, which heightens the risk for hypoxia. An increase of RVP also elevates transmural pressure, which in turn heightens the risk for retinal edema. In patients with RVO, a high level of RVP may not only be a consequence but also a potential cause of the occlusion; therefore, it risks causing a vicious circle. Narrow retinal arteries and particularly dilated retinal veins are known risk indicators for future cardiovascular events. As the major cause for such a retinal venous dilatation is an increased RVP, RVP may likely turn out to be an even stronger predictor.

Evaluation of the Effect of Hypercapnia on Vascular Function in Normal Tension Glaucoma

INTRODUCTION

Altered ocular perfusion and vascular dysregulation have been reported in glaucoma. The aim of this paper was to evaluate the vascular response to a hypercapnic stimulus.

METHODS

Twenty normal tension glaucoma (NTG) patients and eighteen age- and gender-matched controls had pulsatile ocular blood flow (POBF) measurements, systemic cardiovascular assessment, and laser Doppler digital blood flow (DBF) assessed. Measurements were taken at baseline, after 10-minutes rest, in the stable sitting and supine positions and following induction and stabilization of hypercapnia, which induced a 15% increase in end-tidal pCO2. The POBF response to hypercapnia was divided into high (>20%) and low responders (<20%).

RESULTS

65% of NTG patients had a greater than 41% increase in POBF following CO2 rebreathing (high responders). These high responders had a lower baseline POBF, lower baseline DBF, and a greater DBF response to thermal stimulus.

CONCLUSION

NTG patients that have a greater than 20% increase in POBF after a hypercapnic stimulus have lower baseline POBF and DBF values. This suggests that there is impaired regulation of blood flow in a significant subgroup of NTG patients. This observation may reflect a generalised dysfunction of the vascular endothelium.

Altered retinal flicker response indicates microvascular dysfunction in women with preeclampsia

Flicker-induced dilatation is reduced in patients with cardiovascular risk, and the following arteriolar constriction is reduced with aging, leading to a reduced arteriolar amplitude and, thereby, indicating microvascular endothelial dysfunction. As endothelial dysfunction is associated with preeclampsia, we assessed retinal flicker response during pregnancy and postpartum. Between 2006 and 2013, women were recruited from University Hospital Jena and Prenatal Diagnostic Center Erfurt, Germany, of which 34 women with preeclampsia, 45 women with normal pregnancy, and 22 nonpregnant controls were included in the study. Women with normal pregnancy were matched for age, nulliparity, smoking, previous gestational hypertensive disorders, and family history of cardiovascular disease. Nonpregnant women were age-matched, nulliparous, nonsmoking, without family history of cardiovascular disease. Retinal vessel measurement using Dynamic Vessel Analyzer consisted of 50-seconds baseline acquisition, followed by three 20-second flicker and 80-second relaxation periods. Arteriolar constriction and arteriolar amplitude were reduced during pregnancy (P=0.001 and P=0.008) and postpartum (P=0.018 and P=0.034) in women with preeclampsia, adjusted for age, body mass index, mean arterial pressure, baseline diameter, and family history of cardiovascular disease. Flicker-induced dilatation was unchanged within the groups and throughout the study period. The unchanged flicker-induced dilatation may support a preserved autoregulatory competence of the microvasculature, and the diminished arteriolar amplitude, mainly because of the absence of the arteriolar constriction, indicates a commenced retinal microvascular dysfunction in women with preeclampsia during pregnancy and postpartum. Mechanisms responsible for altered retinal flicker response in preeclampsia need to be clarified in further studies.

Neurocardiovascular instability may modulate end-organ damage: A review of this hypothesis investigating the eye and manifestations of NCVI

Neurocardiovascular instability (NCVI) represents age-related changes in blood pressure and heart rate behaviour. It has been associated with increased leukoaraiosis in the brain and also conditions which are likely to be are related to cerebral end-organ damage, such as stroke and falls. The eye is a 'window' into the brain and cardiovascular (CV) system, changes in retinal microvasculature being independently predictive of cardiovascular events. The eye is highly vascular, having two circulatory systems and as such the ideal target end-organ to investigate NCVI and early end-organ damage. The retinal and choroidal circulations of the eye would be vulnerable to NCVI if ocular vasoregulation becomes impaired with age, particularly given the high metabolic activity of the retina. The choroid is predominantly extrinsically regulated by the autonomic nervous system. In patients with NCVI, autonomic dysfunction is more common and thus impairment of the tightly regulated ocular microcirculation may indeed be compromised. We review the evidence for the hypothesis that NCVI may modulate end-organ cardiovascular pathology and that the eye is the ideal target organ to monitor this.

Optic nerve head biomechanics in aging and disease

This nontechnical review is focused upon educating the reader on optic nerve head biomechanics in both aging and disease along two main themes: what is known about how mechanical forces and the resulting deformations are distributed in the posterior pole and ONH (biomechanics) and what is known about how the living system responds to those deformations (mechanobiology). We focus on how ONH responds to IOP elevations as a structural system, insofar as the acute mechanical response of the lamina cribrosa is confounded with the responses of the peripapillary sclera, prelaminar neural tissues, and retrolaminar optic nerve. We discuss the biomechanical basis for IOP-driven changes in connective tissues, blood flow, and cellular responses. We use glaucoma as the primary framework to present the important aspects of ONH biomechanics in aging and disease, as ONH biomechanics, aging, and the posterior pole extracellular matrix (ECM) are thought to be centrally involved in glaucoma susceptibility, onset and progression.

Study of perfusion changes in the optic disc of patients with fibromyalgia syndrome using new colorimetric analysis software

PURPOSE

We measured the amount of hemoglobin at the optic nerve head of fibromyalgia (FM) patients using new colorimetric analysis software. We also investigated whether perfusion defects of the optic nerve head in patients with FM lead to tissue atrophy and corresponding retinal nerve fiber layer (RNFL) thinning measured by optical coherence tomography (OCT).

METHODS

We recruited for this cross-sectional study 118 FM patients and 76 sex- and age-matched healthy controls. All subjects underwent a complete neuro-ophthalmologic examination, which also included visual field testing using the Spark strategy in an Easyfield perimeter, and OCT examinations using the Spectralis. One photograph of the optic disc was obtained using a Cirrus™ Photo 800 multi-modality imager. We analyzed fundus photographs using Laguna ONhE software, a new method that allows hemoglobin levels to be measured at the optic nerve head. We compared hemoglobin percentages in different sectors of the nerve head and RNFL thicknesses between the two groups.

RESULTS

Mean hemoglobin percentages and hemoglobin content in all optic nerve head sectors calculated by the Laguna ONhE program were significantly lower in FM patients than in healthy controls, and the main differences were detected in the outer ring, which corresponds with the neuroretinal rim. However, only the differences in the superotemporal RNFL were statistically significant. Correlations between the RNFL thickness and the percentage of hemoglobin in the different sectors were weak.

CONCLUSION

Optic disc perfusion was decreased in patients with FM, especially within the neuroretinal rim, without clear involvement in the RNFL.

Patients with diabetic retinopathy have high retinal venous pressure

Background

The introduction of ophthalmodynamometric measurement of retinal venous pressure (RVP) now permits the quantification, or at least an approximation, of the real pressure in the retinal veins.

Methods

We measured the RVP of healthy control subjects, patients with diabetes without diabetic retinopathy (nonDR) and patients with diabetes and diabetic retinopathy (DR).

Results

The mean ± SD RVP for the control, nonDR and DR groups were 23.4 ± 7.33, 22.5 ± 5.78 and 37.7 ± 10.1 mmHg, respectively. In the diabetes patients with DR, the RVP was markedly and significantly increased, and this result was significantly age dependent. RVP was not increased in the group of diabetes patients without DR. In our tested population, diabetes had a minor influence on intraocular pressure.

Conclusion

Regardless of the cause, a marked increase in RVP in diabetes patients with DR is clinically relevant, as it reduces perfusion pressure and increases transmural pressure. The reduced perfusion pressure contributes to hypoxia, and the increased transmural pressure can facilitate retinal edema.

Diabetes is an increasing burden, and DR is one of its most severe complications. Strategies to recognize the risk for DR and to develop personalized prevention and therapy therefore have major implications.

Trial registration

ClinicalTrials.gov ID: NCT01771835.

Macular and peripapillary retinal nerve fibre layer thickness in patients with cyanotic congenital heart disease

PURPOSE

To evaluate macular and retinal nerve fibre layer (RNFL) measurements in patients with cyanotic congenital heart disease (cCHD) using spectral domain optical coherence tomography (OCT).

PATIENTS AND METHODS

Thirty patients with cCHD (18 females and 12 males, mean age 10.9 years) and 60 healthy controls (35 females and 25 males, mean age 11.2 years) underwent complete ophthalmologic examination and OCT measurements of macular and peripapillary RNFL thickness.

RESULTS

Patients with cCHD had significantly thinner measurements in all macular subfields compared with healthy controls (P<0.001). There was no significant difference in peripapillary RNFL thickness between the two groups, with the exception of the upper quadrant, for which thickness measurements were higher in patients with cCHD (P=0.021).

CONCLUSIONS

Patients with cCHD showed a significant decrease in macular thickness and a thickened superior quadrant RNFL thickness when compared with healthy controls. This may represent the damage caused by the effect of hypoxia.

The effect of flammer-syndrome on retinal venous pressure

BACKGROUND

The purpose of the study was to measure the retinal venous pressure (RVP) in the eyes of primary open-angle glaucoma (POAG) patients and healthy subjects with and without a Flammer-Syndrome (FS).

METHODS

RVP was measured in the following four groups of patients and age- and sex-matched healthy controls: (a) 15 patients with a POAG and a FS (POAG/FS+); (b) 15 patients with a POAG but without a FS (POAG/FS-); (c) 14 healthy subjects with a FS (healthy/FS+) and (d) 16 healthy subjects without a FS (healthy/FS-). RVP was measured in all participants bilaterally by means of contact lens ophthalmodynamometry. Ophthalmodynamometry is done by applying increasing pressure on the eye via a contact lens. The minimum force required to induce a venous pulsation is called ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP].

RESULTS

The participants with a FS (whether patients with POAG or healthy subjects), had a significantly higher RVP compared to subjects without a FS (p = 0.0103). Patients with a POAG and FS (POAG/FS+) had a significantly higher RVP compared to patients without a FS (POAG/FS-) (p = 0.0301). There was a notable trend for a higher RVP in the healthy/FS + group compared to the healthy/FS - group, which did not reach statistical significance (p = 0.0898).

CONCLUSIONS

RVP is higher in subjects with a FS, particularly in glaucoma patients. The causal relationship needs to be further evaluated.

Angiotensin II-related hypertension and eye diseases

Systemic vascular disease, especially hypertension, has been suspected as a risk factor for some eye diseases including, diabetic retinopathy and age-related macular degeneration. Hypertension can contribute to chronic diseases by hemodynamic injury and/or cellular actions induced by hypertension-related hormones or growth factors. Among the most important is Angiotensin II (Ang II), which controls blood pressure and induces different cellular functions that may be dependent or independent of its effect on blood pressure. Importantly, as is true for heart, kidney and other organs, the renin-angiotensin system (RAS) is present in the eye. So, even in the absence of hypertension, local production of Ang II could be involved in eye diseases. The goal of this manuscript is to review the most relevant scientific evidence supporting the role of the RAS activation, in the development of age-related macular degeneration and diabetic retinopathy, and highlight the importance of Ang II in the etiology of these diseases.

Relationship between Body Mass Index, Blood Pressure, and Visual Acuity in Residents of Esan West Local Government Area of Edo State, Nigeria

Aim. To study the relationship between body mass index (BMI) and blood pressure (BP) on visual acuity among apparently healthy residents of Ekpoma, Esan West Local Government Area of Edo State, Nigeria. Methodology. This is a cross-sectional descriptive study among 225 subjects (ages of 18–35 years) from whom BP, body weight, and height were collected. Visual acuity was measured using the Snellen chart following standard procedures of number of letters seen at 6-metre distance. The data were then analyzed using SPSS version 17. Results. The sampled population consists of 112 male and 113 female (mean age 31.72±14.2 years). Majority (180) of the respondents had normal visual acuity. However, compared with the respondents with normal BMI (R19.61±1.5; L19.67±1.70), visual acuity of underweight (R18.53±2.30; L18.53±2.70) and obese (R15.68±4.79; L17.73±1.70) were more deviated. Similarly, compared with respondent with normal BP (120–125/80–85 mmHg; R18.00±2.53; L18.07±3.11), hypotensive (R15.5±7.35; L15.00±10.20), and hypertensive (R15.01±21.25; L15.00±11.91) respondents had deviated visual acuity. Conclusion. Abnormal body weight (underweight and obese) and BP (hypotension and hypertension) have potential negative impacts on visual acuity. Based on the observed relationship between weights, BP, and visual acuity, eye examinations can be included as regular screening exercise for abnormal BMI and BP conditions.

[Hemodynamic component in glaucoma and its association with risk factors and cardiovascular disease]

BACKGROUND AND OBJECTIVE

We sought to study the association of glaucoma with vascular disease, with 2 independent pathways: the association of glaucoma with cardiovascular disease (CVD) and the study of ocular hemodynamic variables (OHV) in glaucoma.

MATERIAL AND METHOD

Cross-sectional study consisting of 73 patients: 25 without glaucoma, 28 primary open-angle glaucoma (POAG) and 20 normal-tension glaucoma (NTG). OHV, cardiovascular risk factors (CVRF) and CVD were determined.

RESULTS

We found a greater number of CVRF and CVD in patients affected by POAG (P=.002 and P=.016) and NTG (P=.001 and P=.010) compared to the control group. With regard to OHV, in patients suffering from POAG, we found lower systolic and diastolic velocities and higher resistance index in the central retinal artery (P<.05). Moreover, in both types of glaucoma, we found higher resistance index in the posterior ciliary artery (P<.05).

CONCLUSIONS

There is a statistically significant association between the presence of CVD and/or CVRF and glaucomatous disease, a finding that is supplemented with data from the OHV. These values indicate a worst ocular perfusion in patients with glaucomatous disease.

A rat experimental model of glaucoma incorporating rapid-onset elevation of intraocular pressure

Glaucoma is a chronic disease that causes structural and functional damage to retinal ganglion cells (RGC). The currently employed therapeutic options are not sufficient to prevent vision loss in patients with glaucoma; therefore, there is a need to develop novel therapies, which requires the creation of functional, repeatable and easy-to-utilize animal models for use in pre-clinical studies. The currently available models ensure only low to moderate damage in optic nerves, with high variation in the outcomes and poor repeatability. We have developed an effective and reproducible rat glaucoma model based on a previous idea for a "Bead Model" in mice, which could be useful in future glaucoma research. Additionally, in an attempt to achieve rapid elevation of Intraocular Pressure (IOP), we included an initial "high-pressure injury" as part of this method, which serves as the equivalent of a severe glaucoma attack. These modifications made it possible to achieve longer lasting IOP elevation with chronic damage of retinal ganglion cells.

Flammer syndrome

The new term Flammer syndrome describes a phenotype characterized by the presence of primary vascular dysregulation together with a cluster of symptoms and signs that may occur in healthy people as well as people with disease. Typically, the blood vessels of the subjects with Flammer syndrome react differently to a number of stimuli, such as cold and physical or emotional stress. Nearly all organs, particularly the eye, can be involved. Although the syndrome has some advantages, such as protection against the development of atherosclerosis, Flammer syndrome also contributes to certain diseases, such as normal tension glaucoma. The syndrome occurs more often in women than in men, in slender people than in obese subjects, in people with indoor rather than outdoor jobs, and in academics than in blue collar workers. Affected subjects tend to have cold extremities, low blood pressure, prolonged sleep onset time, shifted circadian rhythm, reduced feeling of thirst, altered drug sensitivity, and increased general sensitivity, including pain sensitivity. The plasma level of endothelin-1 is slightly increased, and the gene expression in lymphocytes is changed. In the eye, the retinal vessels are stiffer and their spatial variability larger; the autoregulation of ocular blood flow is decreased. Glaucoma patients with Flammer syndrome have an increased frequency of the following: optic disc hemorrhages, activated retinal astrocytes, elevated retinal venous pressure, optic nerve compartmentalization, fluctuating diffuse visual field defects, and elevated oxidative stress. Further research should lead to a more concise definition, a precise diagnosis, and tools for recognizing people at risk. This may ultimately lead to more efficient and more personalized treatment.

Retinal venous pressure in the non-affected eye of patients with retinal vein occlusions

BACKGROUND

To measure the retinal venous pressure (RVP) in both eyes of patients with unilateral central retinal vein occlusions and to compare these values to controls.

METHODS

The study included 31 patients with unilateral central retinal vein occlusions (CRVO) and 31 controls who were matched by age, sex, and systemic disease. RVP was measured in all patients bilaterally by means of contact lens ophthalmodynamometry, and the RVP measurements of the affected and unaffected eyes of patients were compared to the RVPs of controls. Ophthalmodynamometry is done by applying an increasing pressure on the eye via a contact lens. The minimum force required to induce a venous pulsation is called ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP].

RESULTS

The RVP group means ± SD were as follows: patient's affected eyes (45.0 ± 11.6 mmHg), patient's unaffected eyes (38.0 ± 11.1 mmHg) ,and (17.7 ± 6.7 mmHg) in the eyes of controls. The values of RVP, even in the patients unaffected eyes, were significantly higher than in the eyes of controls (P < 0.001).

CONCLUSIONS

In patients with CRVO, the RVP is increased in both the affected as well as in the unaffected contralateral eye.

Relationship between ocular surface temperature and peripheral vasoconstriction in healthy subjects: A thermographic study

An impairment of ocular blood flow regulation is commonly considered one of the main pathogenetic mechanisms involved in the development of several eye diseases, like glaucoma. The aim of this study was to investigate whether an alteration of ocular blood supply induced by peripheral vasoconstriction might be detected by measuring the ocular surface temperature. The ocular surface temperature was evaluated in a group of 38 healthy young subjects (28 males and 10 females; mean age: 25.4 ± 4.1 years) by infrared thermography. For each subject, the experimental procedure consisted of two thermographic acquisitions both lasting 10 s, recorded before and during the immersion of both hands in a mixture of ice and water (1.6 °C ± 0.4 °C). Specifically, the second acquisition began 20 s after the hand immersion. Analysis of variance was used to compare the ocular surface temperature of the two profiles. The analysis of infrared images was carried out every 2 s: at the eye opening (t0) until 10 s (t5), for both profiles. Data showed that ocular surface temperature increased significantly ( p-value < 0.05), especially near the sources of ocular blood supply, that is, temporal and nasal areas (mean increasing temperature at t0 for P1 = 0.12 °C ± 0.13 °C). Therefore, these results suggest a response of the ocular hemodynamic to the peripheral vasoconstriction. The ocular surface temperature may represent a cheap, non-invasive and non-time-consuming test to evaluate ocular vaso-regulation.

Reliability and validity of digital assessment of perifoveal capillary network measurement using high-resolution imaging

BACKGROUND

Assessment of the perifoveal capillary network (PCN) might indicate macular function and could reflect the systemic microcirculation. The quantification and reliability of this measurement is currently unknown. The aim of this study was to validate quantification of the PCN by a non-invasive technique from high-resolution retinal images.

METHODS

Ten healthy volunteers were included in this validation study. At least 320 high-resolution retinal images were used for assessment of inter- and intra-observer reliability. Non-invasive capillary perfusion mapping was performed using a retinal function imager. After the images were enhanced and segmented, the reproducibility was verified by comparing the values of two independent examiners and of a single examiner at two different time points.

RESULTS

The inter-observer concordance coefficients were highly significant for PCN (intraclass correlation coefficient (ICC)=0.901, 95% CI 0.655 to 0.975, p<0.001) and normalised PCN (ICC=0.727, 95% CI 0.262 to 0.923, p=0.004). The intra-observer measurements at two different time points were also highly concordant for PCN (ICC=0.879, 95% CI 0.598 to 0.968, p<0.001) and for normalised PCN (ICC=0.960, 95% CI 0.851 to 0.990, p<0.001).

CONCLUSIONS

The reliability of PCN measurement is reproducible and could be used as a new tool to quantify the capillary perfusion network of the macular area.

The primary vascular dysregulation syndrome: implications for eye diseases

Vascular dysregulation refers to the regulation of blood flow that is not adapted to the needs of the respective tissue. We distinguish primary vascular dysregulation (PVD, formerly called vasospastic syndrome) and secondary vascular dysregulation (SVD). Subjects with PVD tend to have cold extremities, low blood pressure, reduced feeling of thirst, altered drug sensitivity, increased pain sensitivity, prolonged sleep onset time, altered gene expression in the lymphocytes, signs of oxidative stress, slightly increased endothelin-1 plasma level, low body mass index and often diffuse and fluctuating visual field defects. Coldness, emotional or mechanical stress and starving can provoke symptoms. Virtually all organs, particularly the eye, can be involved. In subjects with PVD, retinal vessels are stiffer and more irregular, and both neurovascular coupling and autoregulation capacity are reduced while retinal venous pressure is often increased. Subjects with PVD have increased risk for normal-tension glaucoma, optic nerve compartment syndrome, central serous choroidopathy, Susac syndrome, retinal artery and vein occlusions and anterior ischaemic neuropathy without atherosclerosis. Further characteristics are their weaker blood–brain and blood-retinal barriers and the higher prevalence of optic disc haemorrhages and activated astrocytes. Subjects with PVD tend to suffer more often from tinnitus, muscle cramps, migraine with aura and silent myocardial ischaemic and are at greater risk for altitude sickness. While the main cause of vascular dysregulation is vascular endotheliopathy, dysfunction of the autonomic nervous system is also involved. In contrast, SVD occurs in the context of other diseases such as multiple sclerosis, retrobulbar neuritis, rheumatoid arthritis, fibromyalgia and giant cell arteritis. Taking into consideration the high prevalence of PVD in the population and potentially linked pathologies, in the current article, the authors provide recommendations on how to effectively promote the field in order to create innovative diagnostic tools to predict the pathology and develop more efficient treatment approaches tailored to the person.

In vivo imaging of human retinal microvasculature using adaptive optics scanning light ophthalmoscope fluorescein angiography

The adaptive optics scanning light ophthalmoscope (AOSLO) allows visualization of microscopic structures of the human retina in vivo. In this work, we demonstrate its application in combination with oral and intravenous (IV) fluorescein angiography (FA) to the in vivo visualization of the human retinal microvasculature. Ten healthy subjects ages 20 to 38 years were imaged using oral (7 and/or 20 mg/kg) and/or IV (500 mg) fluorescein. In agreement with current literature, there were no adverse effects among the patients receiving oral fluorescein while one patient receiving IV fluorescein experienced some nausea and heaving. We determined that all retinal capillary beds can be imaged using clinically accepted fluorescein dosages and safe light levels according to the ANSI Z136.1-2000 maximum permissible exposure. As expected, the 20 mg/kg oral dose showed higher image intensity for a longer period of time than did the 7 mg/kg oral and the 500 mg IV doses. The increased resolution of AOSLO FA, compared to conventional FA, offers great opportunity for studying physiological and pathological vascular processes.