Ocular perfusion and age-related macular degeneration

Age-Related Macular Degeneration Choroidal Vascular Distribution Characteristics Based on Indocyanine Green Angiography

Purpose

The purpose of this study was to present our findings of the distribution pattern of choroidal arteries and large veins in patients with age-related macular degeneration (AMD) using indocyanine green angiography (ICGA).

Methods

A retrospective analysis was conducted on 980 patients who underwent ICGA at The Second Affiliated Hospital of Xi'an Jiaotong University from 2017 to 2023, including 240 patients with AMD. Secondary image processing was applied to the angiographic videos to obtain posterior distribution maps of choroidal arteries and large veins. Differences between different distribution patterns regarding age, gender, eye laterality, and circulation time were compared. We also conducted a comparison of choroidal vascular distribution characteristics between patients with AMD and patients with diabetic retinopathy (DR) and provided a summary of choroidal vascular distribution patterns in AMD.

Results

The filling patterns of choroidal arteries can be classified into the invisible trunk arteries type, the partially masked trunk arteries type, and the exposed trunk arteries type. The vascular topography of the large choroidal vein can be classified into the watershed type, the non-watershed type, and the unknown type, further divided into six subtypes. The distribution patterns of choroidal arteries and veins were significantly correlated with age (P < 0.001). Left eye, older age, and the exposed trunk arteries type were independent risk factors for non-watershed large choroidal vein (P < 0.05). The non-watershed type was the main characteristic of the venous phase in AMD.

Conclusions

The distribution characteristics of the arterial and venous patterns in AMD suggest atrophy of the small blood vessels in the choroid and insufficient perfusion pressure of the blood flow.

Exploring the pathogenesis of age-related macular degeneration: A review of the interplay between retinal pigment epithelium dysfunction and the innate immune system

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss in the older population. Classical hallmarks of early and intermediate AMD are accumulation of drusen, a waste deposit formed under the retina, and pigmentary abnormalities in the retinal pigment epithelium (RPE). When the disease progresses into late AMD, vision is affected due to death of the RPE and the light-sensitive photoreceptors. The RPE is essential to the health of the retina as it forms the outer blood retinal barrier, which establishes ocular immune regulation, and provides support for the photoreceptors. Due to its unique anatomical position, the RPE can communicate with the retinal environment and the systemic immune environment. In AMD, RPE dysfunction and the accumulation of drusen drive the infiltration of retinal and systemic innate immune cells into the outer retina. While recruited endogenous or systemic mononuclear phagocytes (MPs) contribute to the removal of noxious debris, the accumulation of MPs can also result in chronic inflammation and contribute to AMD progression. In addition, direct communication and indirect molecular signaling between MPs and the RPE may promote RPE cell death, choroidal neovascularization and fibrotic scarring that occur in late AMD. In this review, we explore how the RPE and innate immune cells maintain retinal homeostasis, and detail how RPE dysfunction and aberrant immune cell recruitment contribute to AMD pathogenesis. Evidence from AMD patients will be discussed in conjunction with data from preclinical models, to shed light on future therapeutic targets for the treatment of AMD.

Ageing fundus degenerations of Macaca fascicularis on multi-modal imaging and histopathology: Similarities and differences compared to human

To characterize the ageing fundus degenerations in Macaca fascicularis, we used multimodal imaging including color fundus photograph, spectral domain optical coherence tomography, fundus autofluorescence, fundus fluorescence angiography, and indocyanine green angiography (ICGA) to survey and track fundus changes of 84 Macaca fascicularis, ranging from 5 to 24 years old over 2 years, and followed by hematoxylin-eosin (HE) and immunofluorescence (IF) staining. The Macaca fascicularis in our cohort showed ageing characteristics different from human, including the more common yellow dot maculopathy, the unique appearance of patchy hyperautoflurescence, and the absence of subretinal drusenoid deposit, basal laminar deposit, geographic atrophy or choroidal neovascularization. Same with human, hard drusen, soft drusen, atherosclerosis, tessellated retina, staining of vessels in peripheral choroid on late-phase ICGA, and peripheral hard drusen were detected. HE and IF staining suggested the patchy hyperautoflurescence to be drusenoid deposits. BMI were significantly higher in the Macaca fascicularis with yellow dot maculopathy and hard drusen, compared to the ones without (p < 0.05). Our study reveals fundus degenerations that develop with ageing in the nonhuman primate of Macaca fascicularis. Their differences and similarities compared to human worth notice by future translational research in degenerative fundus diseases, especially age-related macular degeneration.

Association of Smoking, Alcohol Consumption, Blood Pressure, Body Mass Index, and Glycemic Risk Factors With Age-Related Macular Degeneration: A Mendelian Randomization Study

IMPORTANCE

Advanced age-related macular degeneration (AMD) is a leading cause of blindness in Western countries. Causal, modifiable risk factors need to be identified to develop preventive measures for advanced AMD.

OBJECTIVE

To assess whether smoking, alcohol consumption, blood pressure, body mass index, and glycemic traits are associated with increased risk of advanced AMD.

DESIGN, SETTING, PARTICIPANTS

This study used 2-sample mendelian randomization. Genetic instruments composed of variants associated with risk factors at genome-wide significance (P < 5 × 10-8) were obtained from published genome-wide association studies. Summary-level statistics for these instruments were obtained for advanced AMD from the International AMD Genomics Consortium 2016 data set, which consisted of 16 144 individuals with AMD and 17 832 control individuals. Data were analyzed from July 2020 to September 2021.

EXPOSURES

Smoking initiation, smoking cessation, lifetime smoking, age at smoking initiation, alcoholic drinks per week, body mass index, systolic and diastolic blood pressure, type 2 diabetes, glycated hemoglobin, fasting glucose, and fasting insulin.

MAIN OUTCOMES AND MEASURES

Advanced AMD and its subtypes, geographic atrophy (GA), and neovascular AMD.

RESULTS

A 1-SD increase in logodds of genetically predicted smoking initiation was associated with higher risk of advanced AMD (odds ratio [OR], 1.26; 95% CI, 1.13-1.40; P < .001), while a 1-SD increase in logodds of genetically predicted smoking cessation (former vs current smoking) was associated with lower risk of advanced AMD (OR, 0.66; 95% CI, 0.50-0.87; P = .003). Genetically predicted increased lifetime smoking was associated with increased risk of advanced AMD (OR per 1-SD increase in lifetime smoking behavior, 1.32; 95% CI, 1.09-1.59; P = .004). Genetically predicted alcohol consumption was associated with higher risk of GA (OR per 1-SD increase of log-transformed alcoholic drinks per week, 2.70; 95% CI, 1.48-4.94; P = .001). There was insufficient evidence to suggest that genetically predicted blood pressure, body mass index, and glycemic traits were associated with advanced AMD.

CONCLUSIONS AND RELEVANCE

This study provides genetic evidence that increased alcohol intake may be a causal risk factor for GA. As there are currently no known treatments for GA, this finding has important public health implications. These results also support previous observational studies associating smoking behavior with risk of advanced AMD, thus reinforcing existing public health messages regarding the risk of blindness associated with smoking.

Bevacizumab in Wet AMD treatment: A tribute to the thirteen years of experience from the beginning of the anti-VEGF era in Romania

This study aimed to identify and describe anatomical and functional changes on short (1–3 months) and medium (6–12 months) term after intravitreal injections of bevacizumab (Avastin, Genentech) in patients with choroidal neovascularization (CNV) in the context of exudative form of age-related macular degeneration (AMD). We performed a retrospective, analytical, interventional study, based on a series of cases with exudative form of AMD, which also comprised a prospective component related to the inclusion and treatment of the patients with a very new interventional method for that time (2006) and the follow-up of the effects of intravitreal injection of bevacizumab (1.25 mg) therapy in three monthly doses for short (1–3 months) and medium (6–18 months) periods of time. The follow-up of these patients was made by determining visual acuity (VA) as best corrected visual acuity (BCVA) at baseline and at every visit, slit lamp examination with contact or noncontact lenses each time, and optical coherence tomography and/or angiofluorography, applied only for certain patients, at various times of the study. In total, 376 intravitreal injections were administered to 117 eyes of 96 patients. The VA improved in the assessment of 3 months in 77 eyes (66%), either subjective (by the patient) or objectively quantified (by the physician). In 40 eyes (34%), there was no change in VA. In patients for whom optical coherence tomography could be performed, a significant reduction of the macula's thickness was found. The use of bevacizumab in subretinal neovascular membrane treatment is effective and safe on short and medium term, with the improvement of BCVA and reduction of macular edema in a significant number of cases.

Defective Choroidal Blood Flow Baroregulation and Retinal Dysfunction and Pathology Following Sympathetic Denervation of Choroid

Purpose

We sought to determine if sympathetic denervation of choroid impairs choroidal blood flow (ChBF) regulation and harms retina.

Methods

Rats received bilateral superior cervical ganglionectomy (SCGx), which depleted choroid of sympathetic but not parasympathetic innervation. The flash-evoked scotopic ERG and visual acuity were measured 2 to 3 months after SCGx, and vasoconstrictive ChBF baroregulation during high systemic arterial blood pressure (ABP) induced by LNAME was assessed by laser Doppler flowmetry (LDF). Eyes were harvested for histologic evaluation.

Results

ChBF increased in parallel with ABP in SCGx rats over an ABP range of 90% to 140% of baseline ABP, while in sham rats ChBF remained stable and uncorrelated with ABP. ERG a- and b-wave latencies and amplitudes, and visual acuity were significantly reduced after SCGx. In SCGx retina, Müller cell GFAP immunolabeling was upregulated 2.5-fold, and Iba1+ microglia were increased 3-fold. Dopaminergic amacrine cell fibers in inner plexiform layer were reduced in SCGx rats, and photoreceptors were slightly depleted. Functional deficits and pathology were correlated with impairments in sympathetic regulation of ChBF.

Conclusions

These studies indicate that sympathetic denervation of choroid impairs ChBF baroregulation during elevated ABP, leading to choroidal overperfusion. This defect in ChBF regulation is associated with impaired retinal function and retinal pathology. As sympathetic ChBF baroregulatory defects have been observed in young individuals with complement factor H (CFH) polymorphisms associated with risk for AMD, our results suggest these defects may harm retina, perhaps contributing to AMD pathogenesis.

Extracellular l-arginine Enhances Relaxations Induced by Opening of Calcium-Activated SKCa Channels in Porcine Retinal Arteriole

We investigated whether the substrate for nitric oxide (NO) production, extracellular l-arginine, contributes to relaxations induced by activating small (SKCa) conductance Ca²⁺-activated potassium channels. In endothelial cells, acetylcholine increased ³H-l-arginine uptake, while blocking the SKCa and the intermediate (IKCa) conductance Ca²⁺-activated potassium channels reduced l-arginine uptake. A blocker of the y+ transporter system, l-lysine also blocked ³H-l-arginine uptake. Immunostaining showed co-localization of endothelial NO synthase (eNOS), SKCa3, and the cationic amino acid transporter (CAT-1) protein of the y+ transporter system in the endothelium. An opener of SKCa channels, cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) induced large currents in endothelial cells, and concentration-dependently relaxed porcine retinal arterioles. In the presence of l-arginine, concentration-response curves for CyPPA were leftward shifted, an effect unaltered in the presence of low sodium, but blocked by l-lysine in the retinal arterioles. Our findings suggest that SKCa channel activity regulates l-arginine uptake through the y+ transporter system, and we propose that in vasculature affected by endothelial dysfunction, l-arginine administration requires the targeting of additional mechanisms such as SKCa channels to restore endothelium-dependent vasodilatation.

Lutein Complex Supplementation Increases Ocular Blood Flow Biomarkers in Healthy Subjects

Introduction: To investigate the effects of a lutein complex supplementation on ocular blood flow in healthy subjects. Materials and Methods: Sixteen healthy female patients (mean age 36.8 ± 12.1 years) were enrolled in this randomized, placebo-controlled, double-blinded, two-period crossover study. Subjects received daily an oral dose of the lutein with synergistic phytochemicals complex (lutein (10 mg), ascorbic acid (500 mg), tocopherols (364 mg), carnosic acid (2.5 mg), zeaxanthin (2 mg), copper (2 mg), with synergistic effects in reducing pro-inflammatory mediators and cytokines when administered together in combination) and placebo during administration periods. Measurements were taken before and after three-week supplementation periods, with crossover visits separated by a three-week washout period. Data analysis included blood pressure, heart rate, intraocular pressure, visual acuity, contrast sensitivity detection, ocular perfusion pressure, confocal scanning laser Doppler imaging of retinal capillary blood flow, and Doppler imaging of the retrobulbar blood vessels. Results: Lutein complex supplementation produced a statistically significant increase in mean superior retinal capillary blood flow, measured in arbitrary units (60, p = 0.0466) and a decrease in the percentage of avascular area in the superior (-0.029, p = 0.0491) and inferior (-0.023, p = 0.0477) retina, as well as reduced systolic (-4.06, p = 0.0295) and diastolic (-3.69, p = 0.0441) blood pressure measured in mmHg from baseline. Data comparison between the two supplement groups revealed a significant decrease in systemic diastolic blood pressure (change from pre- to post-treatment with lutein supplement (mean (SE)): -3.69 (1.68); change from pre- to post-treatment with placebo: 0.31 (2.57); p = 0.0357) and a significant increase in the peak systolic velocity (measured in cm/sec) in the central retinal artery (change from pre- to post-treatment with lutein supplement: 0.36 (0.19); change from pre- to post-treatment with placebo: -0.33 (0.21); p = 0.0384) with lutein complex supplement; data analyses from the placebo group were all non-significant. Discussion: In healthy participants, oral administration of a lutein phytochemicals complex for three weeks produced increased ocular blood flow biomarkers within retinal vascular beds and reduced diastolic blood pressure compared to placebo.

Neural control of choroidal blood flow

The choroid is richly innervated by parasympathetic, sympathetic and trigeminal sensory nerve fibers that regulate choroidal blood flow in birds and mammals, and presumably other vertebrate classes as well. The parasympathetic innervation has been shown to vasodilate and increase choroidal blood flow, the sympathetic input has been shown to vasoconstrict and decrease choroidal blood flow, and the sensory input has been shown to both convey pain and thermal information centrally and act locally to vasodilate and increase choroidal blood flow. As the choroid lies behind the retina and cannot respond readily to retinal metabolic signals, its innervation is important for adjustments in flow required by either retinal activity, by fluctuations in the systemic blood pressure driving choroidal perfusion, and possibly by retinal temperature. The former two appear to be mediated by the sympathetic and parasympathetic nervous systems, via central circuits responsive to retinal activity and systemic blood pressure, but adjustments for ocular perfusion pressure also appear to be influenced by local autoregulatory myogenic mechanisms. Adaptive choroidal responses to temperature may be mediated by trigeminal sensory fibers. Impairments in the neural control of choroidal blood flow occur with aging, and various ocular or systemic diseases such as glaucoma, age-related macular degeneration (AMD), hypertension, and diabetes, and may contribute to retinal pathology and dysfunction in these conditions, or in the case of AMD be a precondition. The present manuscript reviews findings in birds and mammals that contribute to the above-summarized understanding of the roles of the autonomic and sensory innervation of the choroid in controlling choroidal blood flow, and in the importance of such regulation for maintaining retinal health.

Visual acuity loss associated with excessive "dry macula" in exudative age-related macular degeneration

Purpose

To investigate the correlation between visual acuity and central macular thickness (CMT) and choroidal thickness (CCT) in patients with wet age-related macular degeneration (AMD).

Methods

In this retrospective analysis, 14 eyes that received >10 ranibizumab injections (based on pro re nata [PRN] regimen) and maintained initial visual acuity gain were analyzed. The following 5 parameters were measured at the foveal center: CMT (distance from the inner limiting membrane [ILM] to Bruch’s membrane); central retinal thickness (CRT; distance from the ILM to the inner limit of the retinal pigment epithelium or subretinal fluid [SRF]); SRF thickness (SRFT); pigment epithelium detachment thickness (PEDT); and CCT. The correlation between the logarithm of the minimum angle of resolution (logMAR) best-corrected visual acuity (BCVA) and the 5 parameters was examined with generalized estimating equations.

Results

CMT, CRT, and CCT were negatively correlated with logMAR BCVA (P=0.031, 0.023, and 0.036, respectively) when only CMT values less than the thickness that maximized visual acuity for each eye were used for the analysis. Each 100-μm reduction in CMT, CRT, or CCT improved logMAR BCVA by −0.1, −0.08, or −0.07, respectively. SRFT and PEDT were not correlated with BCVA. The median CMT that maximized the visual acuity was 230 μm.

Conclusion

Dry macula with CMT <230 μm was associated with temporary decrease in visual acuity in AMD patients whose visual acuity was maintained with PRN regimen.

Association between open-angle glaucoma and neovascular age-related macular degeneration: a case-control study

PurposeTo investigate the relationship between previously diagnosed open-angle glaucoma (OAG) and neovascular age-related macular degeneration (AMD) using a routine insurance dataset.MethodsThis study retrieved data from the Taiwan Longitudinal Health Insurance Database 2005. We found 3282 patients with neovascular AMD as cases and 13 128 sex- and age-matched subjects without neovascular AMD as controls. Conditional logistic regressions were performed to evaluate the association of neovascular AMD with previously diagnosed OAG among the sampled patients.ResultsOf the 16 410 sampled patients, 2.55% had previously diagnosed OAG, 5.06 and 1.92% for the cases and controls, respectively. The logistic regression analysis showed that the odds ratio (OR) of previously diagnosed OAG for cases was 2.45 (OR: 2.45; 95% confidence interval: 1.99-3.01) compared with the controls after adjusting for potential confounders. In addition, the adjusted ORs for previously diagnosed OAG were similar for patients with AMD in both genders (with an adjusted OR of 2.49 for males and 2.39 for females). Furthermore, it shows that OAG was significantly associated with neovascular AMD regardless of sex even after adjusting for monthly income, geographic region, urbanisation level, and comorbidities (with adjusted ORs of 2.49 for males and 2.39 for females).ConclusionsThis study demonstrated that patients with neovascular AMD had a higher odds of previously diagnosed OAG compared with those patients without neovascular AMD regardless of sex.

Hemorheological parameters and their correlations in OXYS rats: a new model of hyperviscosity syndrome

Rheohaemapheresis aims to normalize major rheological parameters and is used to treat patients with dry age-related macular degeneration (AMD). While effective, this approach is invasive and requires specially trained personnel. Therefore, the search for novel effective compounds with hemorheological properties that can be taken orally to treat AMD is justified. The use of a robust rodent model of AMD with high blood viscosity is crucial to test the efficacy of potential hemorheological drugs to treat this disease. The objective of this study was to investigate whether OXYS rats, generally used as an animal model of AMD, have hyperviscosity syndrome. The results of this study show that blood viscosity in OXYS rats at low (3-10 s -1) and high (45-300 s -1) shear rates were 14-20% and 7-10% higher than in Wistar rats, while hematocrit and plasma viscosity were not different. Red blood cells (RBCs) in OXYS rats were more prone to aggregation as shown by 39% shorter half-time than in Wistar rats. RBCs were also more rigid in OXYS than in Wistar rats as shown by 21-33% lower index of elongation at the shear stress of 1-7 Pa. These data indicate that OXYS rats have hyperviscosity syndrome as the result of abnormal RBC deformability and aggregation. We propose to use OXYS rats as an animal model for preclinical studies to test compounds with hemorheological properties aimed to treat AMD.

Type-specific photoreceptor loss in pigeons after disruption of parasympathetic control of choroidal blood flow by the medial subdivision of the nucleus of Edinger-Westphal

The medial part of the nucleus of Edinger–Westphal (EWM) in birds mediates light-regulated adaptive increases in choroidal blood flow (ChBF). We sought to characterize the effect of loss of EWM-mediated ChBF regulation on photoreceptor health in pigeons housed in either moderate intensity diurnal or constant light (CL). Photoreceptor abundance following complete EWM destruction was compared to that following a lesion in the pupil control circuit (as a control for spread of EWM lesions to the nearby pupil-controlling lateral EW) or following no EW damage. Birds were housed post-lesion in a 12 h 400 lux light/12 h dark light cycle for up to 16.5 months, or in constant 400 lux light for up to 3 weeks. Paraformaldehyde–glutaraldehyde fixed eyes were embedded in plastic, sectioned, slide-mounted, and stained with toluidine blue/azure II. Blinded analysis of photoreceptor outer segment abundance was performed, with outer segment types distinguished by oil droplet tint and laminar position. Brains were examined histologically to assess lesion accuracy. Disruption of pupil control had no adverse effect on photoreceptor outer segment abundance in either diurnal light or CL, but EWM destruction led to 50–60% loss of blue/violet cone outer segments in both light conditions, and a 42% loss of principal cone outer segments in CL. The findings indicate that adaptive regulation of ChBF by the EWM circuit plays a role in maintaining photoreceptor health and mitigates the harmful effect of light on photoreceptors, especially short wavelength-sensitive cone photoreceptors.

Risk factors and biomarkers of age-related macular degeneration

A biomarker can be a substance or structure measured in body parts, fluids or products that can affect or predict disease incidence. As age-related macular degeneration (AMD) is the leading cause of blindness in the developed world, much research and effort has been invested in the identification of different biomarkers to predict disease incidence, identify at risk individuals, elucidate causative pathophysiological etiologies, guide screening, monitoring and treatment parameters, and predict disease outcomes. To date, a host of genetic, environmental, proteomic, and cellular targets have been identified as both risk factors and potential biomarkers for AMD. Despite this, their use has been confined to research settings and has not yet crossed into the clinical arena. A greater understanding of these factors and their use as potential biomarkers for AMD can guide future research and clinical practice. This article will discuss known risk factors and novel, potential biomarkers of AMD in addition to their application in both academic and clinical settings.

Peripapillary choroidal thickness after intravitreal ranibizumab injections in eyes with neovascular age-related macular degeneration

Background

The purpose of this study was to investigate peripapillary choroidal thickness (CT) in eyes with neovascular age-related macular degeneration (AMD) and to assess whether peripapillary CT is affected by intravitreal injection of ranibizumab (IVR) in eyes with neovascular AMD.

Methods

Peripapillary and subfoveal CT were measured in spectral domain optical coherence tomography images from 39 eyes of neovascular AMD patients and 39 eyes of age-matched controls retrospectively. The patients were treated with 0.5 mg IVR monthly for 3 months and retreated as needed. Peripapillary CT at baseline, 3 months and 6 months was measured at four locations (superior, nasal, inferior and temporal areas).

Results

The mean peripapillary and subfoveal baseline CTs of the eyes with neovascular AMD (153.3 ± 45.3 μm and 228.6 ± 78.6 μm) were not different from those of the controls (149.0 ± 42.3 μm and 221.4 ± 54.1 μm; P = 0.665 and P = 0.639, respectively). Subfoveal CT decreased at 3 months (213.8 ± 75.8 μm, P < 0.001) and 6 months (215.1 ± 72.8 μm, P = 0.002) following IVR treatment. Mean peripapillary CT did not show significant changes at 3 months (149.6 ± 43.8 μm, P = 0.156) or 6 months (150.0 ± 43.4 μm, P = 0.187). Subanalysis revealed that only temporal peripapillary CT decreased from baseline (167.1 ± 54.5 μm) to 3 months (159.4 ± 50.8 μm, P = 0.010) and was sustained at 6 months (160.6 ± 49.6, P = 0.026). However, superior, nasal and inferior peripapillary CT did not show significant changes after IVR.

Conclusions

Changes in peripapillary CT after IVR were limited to the macular area. This result may suggest that IVR does not affect CT outside of the macula in the eyes of patients with neovascular AMD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-016-0203-7) contains supplementary material, which is available to authorized users.

Low-level night-time light therapy for age-related macular degeneration (ALight): study protocol for a randomized controlled trial

Background

Age-related macular degeneration (AMD) is the leading cause of blindness among older adults in the developed world. The only treatments currently available, such as ranibizumab injections, are for neovascular AMD, which accounts for only 10 to 15% of people with the condition. Hypoxia has been implicated as one of the primary causes of AMD, and is most acute at night when the retina is most metabolically active. By increasing light levels at night, the metabolic requirements of the retina and hence the hypoxia will be considerably reduced. This trial seeks to determine whether wearing a light mask that emits a dim, green light during the night can prevent the progression of early AMD.

Methods/design

ALight is a Phase I/IIa, multicentre, randomized controlled trial. Sixty participants (55 to 88 years old) with early AMD in one eye and neovascular AMD (nAMD) in the fellow eye will be recruited from nAMD clinics. They will be randomized (in the ratio 1:1), either to receive the intervention or to be in the untreated control group, stratified according to risk of disease progression. An additional 40 participants with healthy retinal appearance, or early AMD only, will be recruited for a baseline cross-sectional analysis. The intervention is an eye mask that emits a dim green light to illuminate the retina through closed eyelids at night. This is designed to reduce the metabolic activity of the retina, thereby reducing the potential risk of hypoxia. Participants will wear the mask every night for 12 months. Ophthalmologists carrying out monthly assessments will be masked to the treatment group, but participants will be aware of their treatment group. The primary outcome measure is the proportion of people who show disease progression during the trial period in the eye with early AMD. A co-primary outcome measure is the rate of retinal adaptation. As this is a trial of a CE-marked device for an off-label indication, a further main aim of this trial is to assess safety of the mask in the cohort of participants with AMD.

Trial registration

International Standard Randomised Controlled Trials Register: ISRCTN82148651

Perivascular mural cells of the mouse choroid demonstrate morphological diversity that is correlated to vasoregulatory function

Objective

Perivascular mural cells of the choroid have been implicated in physiological functioning as well as in retinal disease pathogenesis. However details regarding their form and function are not well understood. We aim to characterize choroidal mural cells in the adult mouse choroid in terms of their distribution and morphology, and correlate these to their contractile behavior.

Methods

Sclerochoroidal flat-mounted explants were prepared from albino transgenic mice in which the α-smooth muscle actin (α-SMA) promoter drives the expression of green fluorescent protein (GFP). α-SMA-expressing smooth muscle cells and pericytes in the living choroid were thereby rendered fluorescent and imaged with confocal microscopy and live-cell imaging in situ.

Results

Choroidal perivascular mural cells demonstrate significant diversity in terms of their distribution and morphology at different levels of the vasculature. They range from densely-packed circumferentially-oriented cells that provide complete vascular coverage in primary arteries to widely-spaced stellate-shaped cells that are distributed sparsely over terminal arterioles. Mural cells at each level are immunopositive for contractile proteins α-SMA and desmin and demonstrate vasoconstrictory contractile movements in response to endothelin-1 and the calcium ionophore, A23187, and vasodilation in response to the calcium chelator, BAPTA. The prominence of vasoregulatory contractile responses varies with mural cell morphology and density, and is greater in vessels with dense coverage of mural cells with circumferential cellular morphologies. In the choriocapillaris, pericytes demonstrate a sparse, horizontal distribution and are selectively distributed only to the scleral surface of the choriocapillaris.

Conclusions

Diversity and regional specialization of perivascular mural cells may subserve varying requirements for vasoregulation in the choroid. The model of the α-SMA-GFP transgenic albino mouse provides a useful and intact system for the morphological and functional study of choroidal mural cells.

Genotype-phenotype associations in neovascular age-related macular degeneration

PURPOSE

To examine associations between recognized genetic susceptibility loci and angiographic subphenotypes of the neovascular variant of age-related macular degeneration (nvAMD).

METHODS

Participants (247 nvAMD, 52 early age-related macular degeneration [AMD], and 103 controls) were genotyped (complement factor H and ARMS2/HTRA1). nvAMD participants were assigned to one of two subcategories: mainly classic or mainly occult (based on the proportions of classic and occult choroidal neovascularization). nvAMD and early AMD were reassigned to two groups based on the extent and severity of drusen (retinal pigment epithelium dysfunction or not). Univariate and multivariate analysis were used to examine for associations between participant characteristics and genetic loci after adjusting for age, smoking status, and history of cardiovascular disease.

RESULTS

Univariate analysis confirmed the known significant associations between AMD stage and age, hypertension, and a history of cardiovascular disease. Those with retinal pigment epithelium dysfunction (F = 5.46; P = 0.02) or a positive smoking history (F = 3.89; P = 0.05) were more likely to have been classified as having mainly an occult rather than a mainly classic lesion. Multivariate analysis showed that significant associations were noted with the number of ARMS2/HTRA1 risk alleles (P < 0.001), smoking (ever vs. never) (P = 0.03), and cardiovascular disease (P = 0.01). With early AMD as the reference category, the mainly classic group exhibited significant associations with the number of ARMS2/HTRA1 risk alleles present (P < 0.001) and cardiovascular disease (P = 0.02). When mainly classic was compared with mainly occult, the latter was associated with the ARMS2/HTRA1 locus (P = 0.02).

CONCLUSION

ARMS2/HTRA1 risk genotype may play a role in determining neovascular subphenotype, whereas genetics/demographics, smoking, and systemic health factors contribute to the development of advanced AMD in the presence of early AMD.

The effects of moxaverine on ocular blood flow in patients with age-related macular degeneration or primary open angle glaucoma and in healthy control subjects

PURPOSE

The phosphodiesterase inhibitor moxaverine has been shown to increase choroidal blood flow (BF) in young healthy subjects. The present study was performed to investigate the effect of intravenously administered moxaverine on ocular BF in patients with age-related macular degeneration (AMD), primary open angle glaucoma (POAG) and in age-matched control subjects.

METHODS

  Twenty patients with AMD, 20 patients with POAG and 20 control subjects were included. Moxaverine 150 mg was applied intravenously over 30 min. BF was measured in the choroid and in the optic nerve head (ONH) using laser-Doppler flowmetry and in retinal vessels combining laser-Doppler velocimetry with retinal vessel analysis before and 30, 60 and 90 min after start of drug administration. BF velocities in the retrobulbar vessels were measured using colour Doppler imaging.

RESULTS

Moxaverine increased choroidal BF by 9 ± 22% (p = 0.012), ONH BF by 13 ± 33% (p = 0.021), mean flow velocity in the ophthalmic artery by 23 ± 34% (p < 0.001) and in the posterior ciliary arteries by 25 ± 35% (p < 0.001). Moxaverine had no significant effect on retinal vessel diameters and retinal BF. There were no significant differences in any of the measured parameters between the three groups.

CONCLUSION

The present study indicates that systemic administration of moxaverine increases choroidal and ONH BF in elderly patients with eye diseases associated with hypoperfusion and in age-matched controls. Further studies in patients are needed to investigate whether long-term treatment with moxaverine is clinically beneficial for patients with ocular diseases.

HTRA1 in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of severe visual impairment and irreversible blindness in most developed countries, affecting more than 50 million of elderly people worldwide. Current treatments, such as intravitreal injection of antiangiogenic agents, mitigate the effect of advanced AMD but cannot completely cure the disease. Comprehensive understanding of the AMD pathological mechanisms is important for the development of new therapies. Previously, we identified a single-nucleotide polymorphism (rs11200638) in the promoter region of the high temperature requirement factor A1 (HTRA1) gene on chromosome 10q26 to be associated with exudative AMD. In further biological studies, we have provided evidence that HTRA1 could be a potential disease-causing gene within the 10q26 locus. In this review, we summarize the pathology of AMD and the molecular function of the HtrA1 protein. Also evaluated are the genetic effects of HTRA1 polymorphism on AMD in different populations and interactions with other AMD-associated genes, especially with the complement factor H (CFH) gene, which was identified for nonexudative AMD. The biological roles of HtrA1 are exhaustively examined on its contribution to the multifactorial pathogenic mechanism of AMD. Although HtrA1 should play a part in AMD pathogenesis, a host of other genetic and environmental factors, known and unknown, is involved and warrants intensive future research.

Age-related impairment in choroidal blood flow compensation for arterial blood pressure fluctuation in pigeons

PURPOSE

Choroidal vessels compensate for changes in systemic blood pressure (BP) so that choroidal blood flow (ChBF) remains stable over a BP range of approximately 40 mm Hg above and below basal. Because of the presumed importance of ChBF regulation for maintenance of retinal health, we investigated if ChBF compensation for BP fluctuation in pigeons fails with age.

METHODS

Transcleral laser Doppler flowmetry was used to measure ChBF during spontaneous BP fluctuation in anesthetized pigeons ranging in age from 0.5 to 17 years (pigeons can live approximately 20 years in captivity).

RESULTS

ChBF in <8-year-old pigeons remained near 100% of basal ChBF at BPs ranging 40 mm Hg above and below basal BP (95 mm Hg). Baroregulation failed below approximately 50 mm Hg BP. In ≥8-year-old pigeons, ChBF compensation was absent at >90 mm Hg BP, with ChBF linearly following BP. Over the 60 to 90 mm Hg range, ChBF in ≥8-year-old pigeons was maintained at 60-70% of young basal ChBF. Below approximately 55 mm Hg, baroregulation again followed BP linearly.

CONCLUSIONS

Age-related ChBF baroregulatory impairment occurs in pigeons, with ChBF linear with above-basal BP, and ChBF failing to adequately maintain ChBF during below-basal BP. Defective autonomic sympathetic and parasympathetic neurogenic control, or defective myogenic control, may cause these baroregulatory defects. In either case, overperfusion during high BP may cause oxidative injury to the outer retina, whereas underperfusion during low BP may result in deficient nutrient supply and waste removal, with both abnormalities contributing to age-related retinal pathology and vision loss.

Blood flow quantification of the human retina with MRI

The purpose of this study was to investigate the feasibility of measuring blood flow to the retina using arterial spin labeling MRI, a quantitative, noninvasive tomographic technique. Blood flow imaging was performed in a single axial slice through both eyes of five healthy volunteers with no history of retinal diseases. The imaging was optimized to minimize the errors from motion and nonuniform magnetic fields caused by proximity to the sinuses. Key hemodynamic factors for flow quantification, including arterial transit delay and the apparent decay time of the signal, were estimated by repeated measurements with different arterial spin labeling timing. A clearly elevated signal, consistent with the anatomical location of the retina, was observed in all subjects. The measured blood flow to a 1 cm × 1.47 cm section of the retina, centered on the fovea, was 1.75 ± 0.54 µL/mm(2) /min (total blood flow of 261 ± 87 µL/min). The arterial transit delay from a labeling plane 5 cm below the slice was 1137 ± 288 ms. These results establish the feasibility of measuring blood flow to the retina with MRI, and support the future characterization of the healthy and diseased ocular circulation with this method.

Metabolic physiology in age related macular degeneration

Ischemia and hypoxia have been implicated in the pathophysiology of age related macular degeneration (AMD). This has mostly been based on studies on choroidal perfusion, which is not the only contributor to retinal hypoxia found in AMD eyes. Other features of AMD may also interfere with retinal oxygen metabolism including confluent drusen, serous or hemorrhagic retinal detachment, retinal edema and vitreoretinal adhesion. Each of these features contributes to retinal hypoxia: the drusen and retinal elevation by increasing the distance between the choriocapillaris and retina; vitreoretinal adhesion by reducing diffusion and convection of oxygen towards and vascular endothelial growth factor (VEGF) away from hypoxic retinal areas. Hypoxia-inducible-factor is known to exist in subretinal neovascularization and hypoxia is the main stimulus for the production of VEGF. Each feature may not by itself create enough hypoxia and VEGF accumulation to stimulate wet AMD, but they may combine to do so. Choroidal ischemia in AMD has been demonstrated by many researchers, using different technologies. Choroidal ischemia obviously decreases oxygen delivery to the outer retina. Confluent drusen, thickening of Bruch's membrane and any detachment of retina or retinal pigment epithelium, increases the distance between the choriocapillaris and the retina and thereby reduces the oxygen flux from the choroid to the outer retina according to Fick's law of diffusion. Retinal elevation and choroidal ischemia may combine forces to reduce choroidal oxygen delivery to the outer retina, produce retinal hypoxia. Hypoxia leads to production of VEGF leading to neovascularization and tissue edema. A vicious cycle may develop, where VEGF production increases effusion, retinal detachment and edema, further increasing hypoxia and VEGF production. Adhesion of the viscous posterior vitreous cortex to the retina maintains a barrier to diffusion and convection currents in the vitreous cavity according to the laws of Fick's, Stokes-Einstein and Hagen-Poiseuille. If the vitreous is detached from the surface of the retina, the low viscosity fluid transports oxygen and nutrients towards an ischemic area of the retina, and cytokines away from the retina, at a faster rate than through attached vitreous gel. Vitreoretinal adhesion can exacerbate retinal hypoxia and accumulation of cytokines, such as VEGF. Vitreoretinal traction can also cause hypoxia by retinal elevation. Conceivably, the basic features of AMD, drusen, choroidal ischemia, and vitreoretinal adhesion are independently determined by genetics and environment and may combine in variable proportions. If the resulting hypoxia and consequent VEGF accumulation crosses a threshold, this will trigger effusion and neovascularization.

Age-related macular degeneration and the aging eye

Age-related macular degeneration (AMD) is an ocular disease that causes damage to the retinal macula, mostly in the elderly. Normal aging processes can lead to structural and blood flow changes that can predispose patients to AMD, although advanced age does not inevitably cause AMD. In this review, we describe changes that occur in the macular structure, such as the retinal pigment epithelium and Bruch's membrane, with advancing age and in AMD. The role of genetics in AMD and age-related changes in ocular blood flow that may play a role in the pathogenesis of AMD are also discussed. Understanding the pathophysiology of AMD development can help guide future research to further comprehend this disease and to develop better treatments to prevent its irreversible central vision loss in the elderly.

Ocular blood flow in diabetes and age-related macular degeneration

The 2 leading causes of blindness in adults in the industrialized nations, diabetic retinopathy and age-related macular degeneration, have been investigated thoroughly with respect to their pathogenesis. In recent years, it has been discovered that dysfunctional ocular microcirculation appears to play a part in the development of both diseases. In diabetic retinopathy, it has been shown that the disease is associated with early retinal vascular dysregulation. In the later states of the disease, retinal tissue hypoxia is a major trigger of sight-threatening neovascularization. In age-related macular degeneration, there is increasing evidence that reduced blood flow in the choroid is associated with the development and progression of the disease. Knowledge of the pathophysiological vascular states underlying these diseases is essential for the assessment and development of future therapies.

Age-related decline in VIP-positive parasympathetic nerve fibers in the human submacular choroid

PURPOSE

An age-related decline in macular choroidal blood flow (ChBF) occurs in humans. Vasodilatory nerve fibers containing vasoactive intestinal polypeptide (VIP) innervate choroidal blood vessels. The current study was conducted to examine the possibility that an age-related loss of these fibers might occur in the submacular choroid in humans, and thus contribute to a decline in ChBF.

METHODS

Macular choroid punches were collected from 35 healthy human donors ranging from 21 to 93 years of age. Choroidal samples were immunolabeled using anti-VIP and the peroxidase-antiperoxidase

METHOD

VIP-positive nerve fiber abundance was quantified in up to 12 fields per punch. Fifty macular punches were analyzed, and results for eye pairs were averaged. Choroidal vessel diameter (ChVD) was measured for these same fields. The relationship between age and vessel diameter or VIP-positive fiber abundance was analyzed. Multivariate statistical models were generated correcting for gender, variables related to the tissue specimens, and potential procedural sources of variability.

RESULTS

The fully adjusted multivariate models showed a significant age-related reduction in both the VIP-positive fiber abundance (P = 0.0003, adjusted R(2) = 0.51) and ChVD (P < 0.0001, adjusted R(2) = 0.63), with slopes of -0.45 and -0.19, respectively. Adjusting for the same variables, VIP-positive fiber abundance showed a significant direct correlation with ChVD.

CONCLUSIONS

The results indicate a significant age-related decline in VIP-positive nerve fibers and vessel diameter in the submacular choroid in disease-free human donor eyes. These findings suggest that a decline in the neural control of ChBF and vessel diameter may explain the reductions in ChBF and its adaptive control observed clinically with aging.

Sustained upregulation of glial fibrillary acidic protein in Müller cells in pigeon retina following disruption of the parasympathetic control of choroidal blood flow

Choroidal blood flow in pigeon eyes is light driven and controlled by a parasympathetic input from ciliary ganglion (CG) neurons that receive input from the medial subdivision of the ipsilateral nucleus of Edinger-Westphal (EWM). EWM lesions diminish basal ChBF and irreversibly prevent ipsilateral light-evoked increases in ChBF, presumably rendering the retina mildly ischemic. To characterize the location, severity, and time course of the retinal abnormality caused by an EWM lesion, we quantitatively analyzed the cellular and regional extent of Müller cell glial fibrillary acidic protein (GFAP) immunolabeling up to nearly a year after an EWM lesion. We found that unilateral EWM lesions greatly increased Müller cell GFAP throughout the entire retinal depth and topographic extent of the affected eye, up to nearly a year post lesion. By contrast, destruction of the pupilloconstrictive pretectum or of the pupilloconstrictive part of lateral EW (EWL) did not appreciably increase Müller cell GFAP. Thus, the large increase in Müller cell GFAP following an EW lesion is attributable to an ongoing defect in choroidal vasodilatory function rather than to chronic pupil dilation. The Müller cell GFAP increase was greater ipsilateral than contralateral to the EWM destruction for the retinal territory deep to the heavily CG-innervated superior and temporal choroid, but not for the retinal territory deep to the poorly CG-innervated inferior and nasal choroid. The GFAP increase was light-dependent, since it did not occur in EW-lesioned birds housed in dim illumination. Our results show that the chronic vascular insufficiency caused by the loss of the EWM-mediated parasympathetic control of choroidal blood flow leads to a significant and sustained increase in retinal Müller cell GFAP. This increase could be a sign of a disturbance in retinal homeostasis that eventually leads to retinal injury and impaired visual function.

Rheopheresis for age-related macular degeneration: clinical results and putative mechanism of action

BACKGROUND

Rheopheresis is being evaluated in a clinical trial. The rationale and available results are presented.

METHODS

We reviewed the literature about the pathophysiology of age-related macular degeneration (AMD) that might support the use of rheopheresis. In addition, we reviewed the previously published results of the use of rheopheresis for AMD.

RESULTS

There appears to be a diffusion barrier caused by accumulation of cross-linked proteins known as advanced macular oxidation products (AMOPS) in AMD. Rheopheresis allows removal of uncross-linked proteins and facilitates antioxidant entry into Bruch's membrane, preventing further accumulation of AMOPS. The Multicenter Investigation of Rheopheresis for AMD (MIRA-1), an ongoing double-masked randomized trial, should determine the efficacy of rheopheresis in preventing the progression of AMD. The interim results, from an analysis of visual acuity data for 43 patients, are encouraging, confirming the potential of rheopheresis as a therapeutic option for dry AMD. The benefit was evident immediately after treatment and remained essentially stable throughout the 12-month period of evaluation. Eyes with late-stage, high-risk, dry AMD appeared to be at significant risk for substantial vision loss over the 12 months if not treated. Subgroup analysis demonstrated that the timing of rheopheresis in the course of a patient's disease may have a pronounced effect on outcome.

INTERPRETATION

There appears to be a rationale for the use of rheopheresis in AMD. Further results of the clinical trial are awaited.

Future pharmacological treatment options for nonexudative and exudative age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in the industrialised world. Within the past decade, researchers have introduced many promising prevention and treatment options in an attempt to minimise the central vision loss imparted from AMD. Based on large-scale, randomised, prospective, placebo-controlled trials, a specially formulated combination of the antioxidants vitamin C, vitamin E, beta-carotene, copper and zinc is the only proven means of AMD prophylaxis. Thermal laser photocoagulation and photodynamic therapy with verteporfin are the only standard treatment options. However, efficacy is limited and treatment is only applicable to a minority of AMD patients. Thus, alternative pharmacological interventions are in all phases of clinical development. Researchers are guardedly optimistic that these advances may change the entire approach to AMD management in the near future. This review article will detail the currently accepted treatment options, as well as describe several of the more promising investigational pharmacological approaches to AMD.

Clinical outcomes and mechanism of action for rheopheresis treatment of age-related macular degeneration (AMD)

The primary goals are to provide a comprehensive explanation of the potential role of therapeutic apheresis in the treatment of Age-Related Macular Degeneration (AMD). Initial clinical results with this technique and a summary of current literature that addresses the mechanism of action for the Rheopheresis approach are presented. Rheopheresis has been found to be a safe and effective application of double filtration plasmapheresis (DFPP) for extracorporeal hemorheotherapy. In this report, it is proposed that Rheopheresis results in an immediate decrease in the proportion of high molecular weight proteins that could combine with the TIMP-3 fibulin complex allowing for the barely functioning retinal pigment epithelial (RPE) cells to function better and diminish the release of vascular endothelial growth factor (VEGF). Interim results from the randomized, double-masked MIRA-1 clinical trial include (1) improved vision restoration; 28.0% of Treated Primary Eyes increased by > or = 2 lines of best corrected visual acuity (BCVA) compared to 18.2% of Placebo Eyes; (2) a decline in progressive vision loss; 0.0% of treated eyes progressing to worse than 20/200 vision over the 12-month study compared to 18.2% of Placebo Eyes; (3) 57.9% of Treatment Eyes obtained improvement in their BCVA to 20/40 or better (driver's license qualification), compared to only 14.3% of Placebo Eyes 12-month post-treatment. Rheopheresis treatment shows strong promise as a viable clinical option for patients suffering from the dry form of AMD in terms of minimizing vision loss, vision restoration, and overall quality of life factors. Expanded clinical outcomes from the ongoing MIRA-1 clinical study will be valuable in the assessment of this new clinical tool for ophthalmic applications.

EVALUATION OF CHOROIDAL PERFUSION OF THE NEW CENTRAL MACULAR AREA BY DILUTION ANALYSIS OFINDOCYANINE GREEN ANGIOGRAPHY AFTER MACULAR TRANSLOCATION

PURPOSE

To evaluate the possible long-term alterations of choroidal perfusion parameters in the new central macular area after macular translocation surgery.

METHODS

Eleven subjects with subfoveal neovascular membrane secondary to age-related macular degeneration or degenerative myopia underwent indocyanine green angiography by using a scanning laser ophthalmoscope before and after macular translocation (mean, 10 months after surgery). Fluorescence intensity of the new central macular area over time was evaluated. Parameters derived from the intensity curves included 10% filling time, ascending slope, and maximal intensity of brightness. The 10% filling time reflects the rapidity of the early choroidal filling phase, whereas the slope of the filling of the curve shows the speed of blood entrance into the choroid. Maximal intensity of brightness indicates vascular density of the area.

RESULTS

No statistical difference was encountered before or after macular translocation in 10% filling time (14.25 +/- 2.09 seconds versus 16.20 +/- 2.95 seconds), slope of the ascending portion of the curve (0.12 +/- 0.04 versus 0.11 +/- 0.04), and maximal intensity of brightness (0.89 +/- 0.09 versus 0.88 +/- 0.07) in the new central macular area. The rotational degree of the retina against the retinal pigment epithelium did not show any significant correlation with 10% filling time, slope, or maximal intensity of brightness.

CONCLUSION

Choroidal perfusion parameters in the new foveal region do not change after macular translocation surgery.

MACULAR TRANSLOCATION SURGERY AND RETINAL CIRCULATION TIMES

PURPOSE

To quantify and compare the retinal circulation times before and after macular translocation surgery.

METHODS

In nine patients undergoing macular translocation with 360-degree retinotomy, arm-retina and arteriovenous passage times were quantified from preoperative and postoperative scanning laser fluorescein angiograms. A control group of eight patients who had not undergone any intraocular surgery was also evaluated. The time that between injection into the antecubital vein and the appearance of fluorescein at two selected points on superotemporal and inferotemporal arteries near the disk provided the arm-retina time. For the arteriovenous passage time, 50% of the maximal fluorescence time difference was assessed from the intensity curves of arteries and corresponding veins at the same points for the arm-retina time. Postoperative measurements were obtained an average of 10.6 months after surgery.

RESULTS

No significant difference was noted between preoperative and postoperative values of the arm-retina time (mean +/- SD: 14.41 +/- 2.73 seconds versus 14.67 +/- 3.85 seconds, respectively; P = 0.84) or that of the arteriovenous passage time (2.66 +/- 0.74 seconds versus 2.47 +/- 0.68 seconds, respectively; P = 0.37) in the study group. The arm-retina time (14.96 +/- 2.01 seconds) and arteriovenous passage time (2.44 +/- 0.68 seconds) in the control group did not differ from preoperative and postoperative arm-retina times (P = 0.65 and P = 0.85) and arteriovenous passage times (P = 0.54 and P = 0.93) in the study group. The arteriovenous passage time correlated with the degree of retinal rotation around the optic disk in the study group (r = -0.70; P = 0.04).

CONCLUSION

Macular translocation surgery does not alter retinal macrocirculation in the long term.

Current and Future Treatment Options for Nonexudative and Exudative Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the industrialised world. Although relatively simple to diagnose through direct visualisation augmented with rapid sequence fluorescein angiography, treatment has presented a far greater challenge because the true aetiology of AMD is largely unknown. Within the past decade, researchers have introduced many new, potentially promising treatment and prevention options in an attempt to minimise the damage imparted from AMD. They capitalise on many of the theoretical and known factors contributing to AMD progression. A high-dose of an orally administered combination of the antioxidants ascorbic acid (vitamin C), tocopherol (vitamin E) and beta-carotene, in addition to copper and zinc, is the only widely accepted preventive therapy. Thermal laser photocoagulation and verteporfin photodynamic therapy are the only standard treatment options available based on large scale, randomised, prospective, placebo-controlled trials; however, efficacy is limited and only a minority of patients who present with AMD are eligible for these treatments. Many other preventive and treatment options are in all phases of clinical studies and expected to change the entire approach to AMD management in the near future. For example, alternative antioxidants, drusen ablation, apheresis and HMG-CoA reductase inhibitors have shown promise in some studies by preventing or slowing the progression of certain forms of AMD. In addition, alternative photodynamic therapies, low-intensity laser, antiangiogenic medications, radiation treatment and surgery have demonstrated the ability, albeit to differing degrees, to inhibit or possibly even reverse the severe vision loss often associated with AMD characterised by choroidal neovascularisation.

Clinical studies to implement Rheopheresis for age-related macular degeneration guided by evidence-based-medicine

In the majority of age-related macular degeneration (AMD) patients the therapeutic situation is very unsatisfactory, especially for patients with dry AMD. Rheopheresis is a safe and effective modality of therapeutic apheresis to treat microcirculatory disorders, and represents a novel therapeutic approach for patients with dry AMD and soft drusen. Elimination of a defined spectrum of high molecular weight proteins from human plasma including pathophysiologically relevant risk factors for AMD such as fibrinogen, LDL-cholesterol, alpha 2-macroglobulin, fibronectin, and von-Willebrand factor results in the reduction of blood and plasma viscosity as well as erythrocyte and thrombocyte aggregation. Pulses of lowering blood and plasma viscosity performed as series of Rheopheresis treatments lead to rapid changes of blood flow, subsequently inducing sustained improvement of microcirculation, and recovery of retinal function. Two controlled randomized clinical trials demonstrated safety and efficacy of Rheopheresis for the treatment of AMD patients, especially with the dry form. Recently the interim-analysis of the sham-controlled, double blinded, randomized multicenter MIRA-I trial confirmed these results. The RheoNet-registry and the development and continuous update of therapy guidelines provide an appropriate framework for the quality management of the interdisciplinary cooperation between ophthalmologists with apheresis specialists. A hypothesis based upon current knowledge of pathogenic mechanisms of the development and progression of AMD can be conclusively linked with the putative mechanism of action of Rheopheresis for AMD. A recommendation for high-risk AMD-patients was defined. Based on the positive results of the MIRA-1 interim analysis eight Rheopheresis treatments are currently recommended as the initial treatment series.

Effects of kallidinogenase on ocular tissue circulation in rabbits

The purpose of this study is to evaluate the effects of kallidinogenase, a tissue kallikrein, on tissue circulation in the optic nerve head (ONH), choroid and retina. Kallidinogenase (1.0 IU/kg) or saline was injected intravenously into urethane-anesthetized rabbits, and the normalized blur value (NB), a quantitative index of in vivo tissue blood velocity, was measured in the ONH, choroid and retina before and for 90 minutes after injection, using the laser speckle method. The difference in NB values in the kallidinogenase group was significantly higher compared with that in the control group in the choroid (p < 0.05) and retina (p < 0.05, ANOVA of repeated measurements). In the ONH, however, there was no significant difference between the kallidinogenase group and the control group except transient increment 10 min after drug administration (p < 0.01, unpaired t-test). On the other hand, systemic condition parameters and intraocular pressure showed no intergroup difference significantly except for a transient decrease in blood pressure and increase in pulse rate in the kallidinogenase groups. Kallidinogenase increased blood velocity, and probably blood flow, in the choroid and retina of rabbits.

Retrobulbar circulation in patients with age-related maculopathy

PURPOSE

To investigate retrobulbar circulation in stages of age-related maculopathy (ARM) and in normal fellow eyes of patients with unilateral exudative ARM.

METHODS

Color Doppler Imaging was used to measure circulatory parameters (peak-systolic velocity--PSV, end-diastolic velocity--EDV, pulsatility index--PI and resistivity index--RI) in the central retinal, posterior ciliary and ophthalmic arteries of 44 patients with age-related maculopathy (ARM) and 32 control subjects. Patients with ARM consisted of 11 with early ARM and 33 with late ARM. Twenty-one patients from the exudative ARM group were also included in a study of unilateral exudative ARM circulation.

RESULTS

In the study of patients with ARM divided into stages, the PI and RI in the posterior ciliary artery of patients with late ARM were significantly higher than that of the control group (P = 0.0064; P = 0.0124). In the early ARM group, circulatory parameters did not differ significantly from those of the control group. In the study of unilateral exudative ARM, the affected eye showed significantly higher RI, as compared to the control group (P = 0.0157), and the fellow eye had significantly decreased EDV as compared to the control group (P = 0.0164). There was no significant difference in circulatory parameters between the affected and normal fellow eyes of patients with unilateral exudative ARM.

CONCLUSION

PI and RI in patients with late ARM and EDV in fellow eyes of patients with unilateral exudative ARM showed significant changes in the posterior ciliary artery compared to normal controls. Altered circulation in the posterior ciliary artery may be involved in the pathogenesis of ARM.

Rheopheresis for age-related macular degeneration: a novel indication for therapeutic apheresis in ophthalmology

Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness in the elderly. Successful therapy is not yet available for the majority of patients, especially not for patients with dry AMD. AMD at cellular and molecular levels is at least in part a microcirculatory disorder of the retina. Rheopheresis is a safe and effective modality of therapeutic apheresis to treat microcirculatory disorders and represents a novel treatment option for patients with dry AMD. Elimination of a defined spectrum of high molecular weight proteins from human plasma including pathophysiologically relevant risk factors for AMD such as fibrinogen, cholesterol, von Willebrand factor, and alpha 2-macroglobulin results in the reduction of blood and plasma viscosity as well as erythrocyte and thrombocyte aggregation. Pulses of lowering blood and plasma viscosity performed as a series of Rheopheresis treatments lead to rapid changes of blood flow, subsequently inducing sustained improvement of microcirculation and recovery of retinal function. Two controlled randomized clinical trials demonstrated the safety and efficacy of Rheopheresis for the treatment of AMD patients, especially for those with the dry form. Recently the interim analysis of the sham-controlled, double blind, randomized multicenter Multicenter Investigation of Rheopheresis for AMD (MIRA-I) trial confirmed these results. The framework of completed and still ongoing controlled clinical trials in combination with postcertification studies including the RheoNet registry represents a comprehensive quality management approach for this novel interdisciplinary therapy for AMD. The development and continuous update of guidelines for the precise indication of Rheopheresis for AMD follows the requirements of evidence-based medicine.

Choroidal perfusion perturbations in non-neovascular age related macular degeneration

AIM

Choroidal perfusion, affected in age related macular degeneration (AMD), is difficult to objectively assess given the overlying retinal circulation. This study more objectively compared choroidal perfusion parameters in a group with non-neovascular AMD to an unaffected age matched control group.

METHODS

21 non-neovascular AMD subjects and 21 age matched control subjects without evidence of AMD underwent assessment of their choroidal blood flow in a case-control study. Scanning laser ophthalmoscope indocyanine green (ICG) angiograms were analysed by a new area dilution analysis technique. Four areas in the perifoveal region and two areas in the temporal peripapillary retina were evaluated by producing a graph of intensity of fluorescence of each area over time. The mean of the filling times and the heterogeneity of the filling times were assessed.

RESULTS

The means of the filling times within the perifoveal regions and the hetereogeneity of the filling times between regions within the same eyes were significantly greater in the AMD patients compared with the control subjects.

CONCLUSIONS

Delayed and heterogeneous filling of the choroid was objectively demonstrated in eyes with non-neovascular AMD compared with age matched controls without evidence of AMD, using an area dilution analysis technique applied to ICG angiography.