CLINICAL AND ELECTROPHYSIOLOGICAL EVALUATION AFTER INTRAVITREAL ZIV-AFLIBERCEPT FOR EXUDATIVE AGE-RELATED MACULAR DEGENERATION

Intravitreal Ziv-Aflibercept versus Bevacizumab for Naïve Central Retinal Vein Occlusion with Macular Edema: An Interim Analysis of a Randomized Non-Inferiority Trial

Purpose

To compare the efficacy of intravitreal ziv-aflibercept (IVZ) and bevacizumab (IVB) injections for the treatment of macular edema secondary to central retinal vein occlusion.

Methods

Participants were randomly assigned 1:1 to receive 3 monthly IVZ (1.25 mg/0.05 mL) or IVB (1.25 mg/0.05 mL) followed by the pro-re-nata protocol for persistent or recurrent macular edema. The primary outcomes were best-corrected visual acuity and central subfield thickness. An interim analysis was planned when half of the participants completed the follow-up.

Results

Twenty-four participants were recruited. At 6 months, mean best-corrected visual acuity in the IVB and IVZ groups improved from 1.23 ± 0.64 to 0.76 ± 0.56 logMAR (p = 0.003) and from 1.13 ± 0.59 to 0.53 ± 0.26 logMAR (p = 0.003), respectively. The percentage of visual improvement and reduction in central subfield thickness in the IVZ group were insignificantly better than those in the IVB group (44.41 ± 26.72 vs 39.64 ± 24.22%; p = 0.65) and (51.94 ± 20.35 vs 45.78 ± 24.71%; p = 0.51), respectively. Although the mean number of injections was lower in the IVZ group (4.55 ± 1.29 vs 4.82 ±1.33), the difference was not statistically significant (p = 0.68). No ocular or systemic adverse events were observed.

Conclusion

The interim analysis demonstrated that the visual and anatomical results of IVZ were insignificantly better than those of IVB at 6 months of follow-up. The results also showed that IVZ was non-inferior to IVB for anatomical improvement but inconclusive for visual improvement.

Clinical Trial Registration

(identifier: TCTR20191205008).

Spectral-domain optical coherence tomography combined with electroretinography in the assessment of conbercept for neovascular age-related macular degeneration: a preliminary study

Objective

To observe the effect of three consecutive intravitreal injections of conbercept in the treatment of neovascular age-related macular degeneration (nAMD), to investigate the correlation between retinal anatomy and retinal function by spectral-domain optical coherence tomography (SD-OCT) and electroretinography (ERG), to evaluate the short-term clinical efficacy of conbercept in the treatment of nAMD, and to explore the value of ERG as a predictor of treatment efficacy.

Method

A retrospective investigation was conducted on 36 patients (36 eyes) treated with intravitreal injections of conbercept at 0.5 mg a month for three consecutive courses. Data collected included the best corrected visual acuity (BCVA), central retinal thickness (CRT), retinal pigment epithelium (RPE) elevation volume in 1 mm-diameter (1RV), 3 mm-diameter (3RV), and 6 mm-diameter circles around the fovea (6RV), amplitude density and latency of the P1 wave in the multifocal electroretinography (mf-ERG) R1 ring and amplitude and latency in full-field electroretinography (ff-ERG) at baseline and monthly. The paired t test was used to compare the difference between pre- and posttreatment. Pearson correlation analysis was used to analyze the correlation between macular retinal structure and function. The difference was significant when p < 0.05.

Results

At 12 weeks, the BCVA, CRT, 1RV, 3RV, 6RV, the P1 wave amplitude density of the mf-ERG R1 ring and the ff-ERG amplitude parameters were all significantly improved (p < 0.001). The BCVA in logMAR was positively correlated with CRT; 1RV, 3RV, and 6RV were negatively correlated with the amplitude density and latency of the mf-ERG R1 ring P1 wave. There were no severe ocular or systemic complications during the follow-up period.

Conclusion

Conbercept is useful for the short-term treatment of nAMD. It can safely improve the visual acuity of affected eyes and restore the structure and function of the retina. ERG could serve as an objective indicator of function for evaluating the efficacy of and determining the need for retreatment during nAMD treatment.

Electrophysiological evaluation and 18-month follow-up of two regimens with aflibercept for neovascular age-related macular degeneration

Purpose

To compare two aflibercept treatment regimens and the electrophysiological outcome concerning cone and rod function in age-related macular degeneration (nAMD) over 18 months.

Methods

41 patients with treatment-naïve nAMD were randomized 1:1 to either arm 1 or 2. Arm 1 received three consecutive monthly aflibercept injections, followed by bimonthly treatment until week 52. Thereafter, a treat-and-extend (TAE) regimen was applied. Arm 2 was treated according to a TAE protocol throughout the 18-month follow-up. We assessed visual acuity (VA), central retinal thickness (CRT), injection rate and interval, and evaluated cone and rod function with full-field and multifocal electroretinography (ffERG, mERG).

Results

There were no statistically significant differences in mean baseline VA, lesion type, age, gender, or symptom duration between the two arms. During the 18-month follow-up, mean VA improved in arm 1 (n = 19) from 63.5 ± 10.5 to 69.1 ± 9.2 letters; p = 0.098; and in arm 2 (n = 20) from 66.8 ± 13.6 to 73.9 ± 9.0 letters; p = .002. In both arms, mean CRT was significantly reduced; p < 0.000. At month 18, we found no significant difference in the number of injections or injection intervals between groups. Arm 1 had received 11.3 ± 1.7 injections vs. 10.9 ± 2.0 in arm 2. The mean injection interval was 9.2 ± 3.4 weeks vs. 9.5 ± 3.1, with 52% (n = 10) on the maximum 12-week interval in arm 1, and 50% (n = 10) in arm 2. The combined rod-cone a-wave amplitude significantly decreased over time; p = 0.043. The isolated rod b-wave amplitude showed a statistically significant decline; p = 0.026. The overall mERG amplitude and implicit time remained unchanged over time; p = 0.878 vs. p = 0.922. The central ring 1 mERG amplitude improved; p = 0.041, with an unaffected implicit time.

Conclusions

After 18 months, both treatments arms have received a similar number of injections at comparable intervals. Electrophysiological evaluation shows no signs of toxicity concerning cone function. But ffERGs for the combined and isolated rod response have declined, possibly reflecting either toxic effects of the drug to rods or the natural course of the disease itself.

An insight on the anatomical and functional consequences of aflibercept therapy in age-related macular degeneration

BACKGROUND

Evaluation of anatomical and functional recovery of the retina after aflibercept therapy in neovascular age-related macular degeneration.

MATERIALS AND METHODS

This prospective study enrolled 33 eyes of 33 naive age-related macular degeneration patients with an average age of 69 (55-82) years. Following a thorough ophthalmological examination, baseline color fundus photography, optical coherence tomography and fluorescein angiography were used to assess the angiographic characteristics and classification of the lesions. Multifocal electroretinography and microperimetry were recorded. In the first three months, all patients received three consecutive intravitreal aflibercept injections on a monthly basis. After the initial three doses, non-responders received additional afibercept injections. The baseline, 3rd and 6th month data were recorded for analysis.

RESULTS

The baseline average best-corrected visual acuity (1.05 log MAR) improved dramatically to 0.9 log MAR in the 3rd and 6th months, respectively. The baseline average central macular thickness of 358.5 ± 232.1 μm decreased significantly to 273.0 ± 109.9 μm and 245.5 ± 109.3 μm in the 3rd and 6th months, respectively. The average thickness of the central 1 mm macular region decreased significantly from 349.5 ± 96.4 μm to the 3rd and 6th month values of 320.6 ± 101.9 and 290.5 ± 86.4 μm, respectively. While the mean retinal sensitivity increased significantly from 4.7 ± 3.0 dB to 6.9 ± 3.4 Db, local deficit decreased from -11.6 ± 4.6 dB to -9.4 ± 4.6 dB. Significant improvements were also observed in all rings of N1 and P1 waves.

CONCLUSION

Intravitreal aflibercept therapy resulted in significant morphological improvements that were easily identifiable during the 3rd month. Electrophysiological improvements were delayed only to become statistically significant in the 6th month. However, it has been shown that visual acuity and optical coherence tomography parameters alone may be insufficient for both the morphological and functional assessment of the retina.

Ziv-aflibercept for Better Regulating Neovascular Age-Related Macular Degeneration (ZEBRA): A Prospective, Randomized Trial

OBJECTIVE

The purpose of this study is to determine if ziv-aflibercept is a safe and effective maintenance drug for nAMD.

STUDY DESIGN AND METHODS

This is a randomized, prospective, single-blinded trial. Inclusion criteria were active nAMD, prior anti-VEGF treatment, and BCVA ≤20/200. The treatment group received ziv-aflibercept. The control group continued their existing anti-VEGF regimen. The main outcome measures were BCVA, CFT, and safety.

RESULTS

Mean baseline BCVA was 1.58 ± 0.44 logMAR and 1.71 ± 0.39 logMAR in the control (n = 27) and treatment (n = 29) groups, respectively. After 24 months, the mean change in BCVA was 0.11 in the control group (equivalent to a loss of 5 ETDRS letters) and 0.01 logMAR in the treatment group (p = .48). Baseline CFT was 257 ± 33 μm and 247 ± 30 μm in the control and treatment groups, respectively, and after 24 months mean change in CFT was 26 μm and -5 μm (p = .24). There were no ocular or systemic adverse events during the study.

CONCLUSION

Ziv-aflibercept is a safe and effective as a maintenance drug for patients with nAMD. It may represent a cost-effective alternative to aflibercept and second-line therapy for eye resistant bevacizumab or ranibizumab.

Ziv-aflibercept: A cost-effective, off-label, highly potent antagonist of vascular endothelial growth factor

Ziv-aflibercept (Zaltrap^® ), a recombinant fusion protein that binds diffusible vascular endothelial growth factor (VEGF), is approved for the treatment of metastatic colorectal carcinoma. Its molecular structure is the same as aflibercept (Eylea^® ), thus making it an attractive option for the off-label treatment of chorioretinal vascular conditions. Ziv-aflibercept is distributed in 4 and 8 ml vials for intravenous use, and its cost after compounding is similar to bevacizumab. Studies with retinal pigment epithelium cytotoxicity, animal histologic sections and electroretinography have demonstrated its safety, and mathematical modelling combined with over four dozen clinical publications from different ophthalmic centres throughout the world attest to its efficacy. No appreciable differences in visual or anatomic outcomes between 1.25 mg (0.05 ml) and 2.5 mg (1.0 ml) doses have been noted. The long duration of action combined with the low cost make ziv-aflibercept an attractive anti-VEGF treatment option, especially in low- and middle-income countries where its popularity is increasing.

INTRAVITREAL ZIV-AFLIBERCEPT FOR NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: 52-Week Results

PURPOSE

To evaluate the 52-week safety and efficacy of intravitreal ziv-aflibercept in patients with neovascular age-related macular degeneration.

METHODS

All patients received three monthly intravitreal injections of 0.05 mL of ziv-aflibercept (1.25 mg) followed by a pro re nata regimen. The best-corrected visual acuity and spectral domain optical coherence tomography were obtained at baseline and monthly. Full-field and multifocal electroretinograms were obtained at baseline and 4, 13, 26, and 52 weeks. For some full-field electroretinography parameters, we calculated the differences between baseline and 52 weeks and then compared those differences between treated and untreated fellow eyes.

RESULTS

Fifteen patients were included and 14 completed the 52-week follow-up. The mean best-corrected visual acuity improved from 0.95 ± 0.41 (20/200) at baseline to 0.75 ± 0.51 (20/125) logarithm of the minimum angle of resolution at 52 weeks (P = 0.0066). The baseline central retinal thickness decreased from 478.21 ± 153.48 μm to 304.43 ± 98.59 μm (P = 0.0004) at 52 weeks. Full-field electroretinography parameters used to assess retinal toxicity after intravitreal injections (rod response and oscillatory potentials) remained unchanged during follow-up. The average multifocal electroretinography macular response in 5° showed increased N1-P1 amplitude and decreased P1 implicit time (P < 0.05). One patient presented with intraocular inflammation after the seventh intravitreal procedure.

CONCLUSION

The results suggested that intravitreal ziv-aflibercept might be safe and effective for treating neovascular age-related macular degeneration. More patients and a longer follow-up are needed to confirm the long-term outcomes of intravitreal ziv-aflibercept.

Comparison of Loading Doses of Ziv-Aflibercept and Aflibercept in Neovascular Age-Related Macular Degeneration

PURPOSE

The aim of this study was to compare outcomes of 3 loading doses of ziv-aflibercept and aflibercept in treatment-naïve neovascular age-related macular degeneration (nAMD).

DESIGN

Retrospective, nonrandomized, comparative study.

METHODS

This was a retrospective chart review which included cases with treatment-naïve nAMD. The patients were divided into 2 groups (group 1, ziv-aflibercept; group 2, aflibercept). Groups 1 and 2 received 1.25 mg/0.05 mL of intravitreal ziv-aflibercept and 2 mg/0.05 mL aflibercept, respectively every month for 3 months. Best-corrected visual acuity (BCVA) in Snellen and logarithm of minimum angle of resolution (logMAR), central subfoveal thickness (CSFT), subretinal hyperreflective material height, neurosensory detachment height, and pigment epithelial detachment height were recorded at baseline and 3 monthly follow-up.

RESULTS

Twenty-three eyes of 23 patients were included (males 14, females 9). Twelve and 11 eyes were included in group 1 and group 2, respectively. Group 1 showed statistically significant improvement in BCVA (P < 0.001) and CSFT (P=0.007) through 3 months compared with baseline. There was significant change in BCVA from baseline at 1st month (P = 0.007), 2nd month (P = 0.002) and 3rd month (P = 0.008). In group 2, there was no significant improvement in BCVA, CSFT, subretinal hyperreflective material height, neurosensory detachment, and pigment epithelial detachment height from baseline through 3 months.

CONCLUSIONS

After 3 loading doses, ziv-aflibercept showed efficacy in terms of improved BCVA and reduction of CSFT from baseline whereas aflibercept did not show such improvement. Considering the cost- effectiveness and the proven safety of ziv-aflibercept, it is a viable option for the crucial, initial 3 doses in the treatment of nAMD.

Role of inflammatory factors in the effects of aflibercept or ranibizumab treatment for alleviating wet age-associated macular degeneration

Aflibercept and ranibizumab are novel drugs for effectively treating wet age-associated macular degeneration (AMD). In the present study, the effect of aflibercept and ranibizumab on wet AMD was compared. A total of 80 AMD patients were intravitreously treated with aflibercept (2.0 mg/dose, 40 participants) or ranibizumab (0.3 mg/dose, 40 participants). The mean visual acuity and central subfield thickness (CTS) were determined at baseline and each follow-up visit (every 4 weeks). ELISA was used to detect the expression of transforming growth factor-β1 (TGF-β1), monocyte chemoattractant protein 1 (MCP-1) and interleukin 6 (IL-6). The primary outcome was the mean change in visual acuity letter score (VAS) and CTS at 1 year. The VAS was markedly improved by 13.1 in the aflibercept group and by 11.0 in the ranibizumab group. In a subgroup of patients with an initial VAS of <69, the mean improvement in the VAS was 17.7 in the aflibercept group and 13.2 in the ranibizumab group (P<0.01). The mean CTS was markedly decreased by 141 in the aflibercept group and by 134 in the ranibizumab group. In the subgroup of patients with an initial VAS of <69, the mean CTS was decreased by 171 in the aflibercept group and by 154 in the ranibizumab group (P<0.01). However, the change of VAS and CTS was similar between the ranibizumab and aflibercept groups when the initial VAS was ≥69. No significant differences in serious adverse events were identified between the aflibercept and ranibizumab groups. The levels of TGF-β1, IL-6 and MCP-1 were decreased by the aflibercept and ranibizumab treatments. The decrease in the levels of the inflammatory factors was more obvious in patients with an initial VAS of <69 in comparison with that in patients with an initial VAS of ≥69. Negative correlations between the levels of TGF-β1, MCP-1 and IL-6 and the mean change of VAS when patients were treated with aflibercept or ranibizumab were identified among all ages. Positive correlations between the levels of TGF-β1, MCP-1 and IL-6 and the mean change of CTS were observed when the initial VAS of the patients was <69. In conclusion, the efficacy of aflibercept in treating patients with AMD was better than that of ranibizumab when the initial VAS of the patients was <69. The inhibition of inflammatory factors may be a secondary effect of aflibercept and ranibizumab treatment. The present study provides a useful reference for the clinical treatment of wet AMD (Chinese Clinical Trial Registry no. ChiCTR1800017782).

Evaluation of aflibercept and ziv-aflibercept binding affinity to vascular endothelial growth factor, stability and sterility after compounding

Purpose

To investigate the binding affinity, stability, and sterility of aflibercept and ziv-aflibercept to vascular endothelial growth factor (Holash et al. in Proc Natl Acad Sci USA 99(17):11393–11398, 2002. 10.1073/pnas.172398299) after compounding and storage for up to 28 days at 4 °C and − 8 °C.

Methods

Tuberculin-type 1-mL syringes were prepared containing aflibercept (40 mg/mL) and ziv-aflibercept (25 mg/mL). Samples were stored at 4 °C and − 8 °C for 0, 14, and 28 days and evaluated for the binding affinity of anti-VEGF to VEGF and stability using enzyme-linked immunosorbent assays. The evaluation of sample sterility was performed.

Results

Laboratory trials with aflibercept and ziv-aflibercept showed preservation of the drug-binding capability to recombinant VEGF when stored in plastic syringes for up to 28 days at 4 °C and − 8 °C. No significant decrease in mass or concentration were observed. Microbiologic evaluations did not detect contamination in the syringes.

Conclusions

The current study corroborates that compounded anti-VEGF drugs aflibercept and ziv-aflibercept do not loose stability or binding affinity and do not become contaminated if prepared under sterile conditions and stored at 4 °C or − 8 °C for 14 or 28 days.

Safety of 5914 intravitreal ziv-aflibercept injections

Purpose

To analyse the pooled safety data of intravitreal ziv-aflibercept (IVZ) therapy for various retinal conditions.

Methods

This was a retrospective, observational study which included patients from 14 participating centres who received IVZ. The medical records of patients who received IVZ from March 2015 through October 2017 were evaluated. Patient demographics and ocular details were compiled. Ocular and systemic adverse events that occurred within 1 month of IVZ injections were recorded and defined as either procedure-related or drug-related.

Results

A total of 1704 eyes of 1562 patients received 5914 IVZ injections (mean±SD: 3.73±3.94) during a period of 2.5 years. The age of patients was 60.6±12.8 years (mean±SD) and included diverse chorioretinal pathologies. Both ocular (one case of endophthalmitis, three cases of intraocular inflammation, and one case each of conjunctival thinning/necrosis and scleral nodule) and systemic adverse events (two cases of myocardial infarction, one case of stroke and two deaths) were infrequent.

Conclusion

This constitutes the largest pooled safety report on IVZ use and includes patients from 14 centres distributed across the globe. It shows that IVZ has an acceptable ocular and systemic safety profile with incidences of adverse events similar to those of other vascular endothelial growth factor inhibitory drugs. The analysis supports the continued use of IVZ in various retinal disorders.

Long-term outcome of treat and extend intravitreal ziv-aflibercept therapy

Aim

To assess the 30-month outcome of treat and extend (TAE) intravitreal ziv-aflibercept therapy in eyes with macular diseases.

Methods

In this prospective study, consecutive subjects received intravitreal 0.05 mL ziv-aflibercept (1.25 mg) injections for various macular diseases. Outcome measures were best-corrected visual acuity (BCVA) (logarithm of the minimum angle of resolution) and central macular thickness (CMT) on spectral domain optical coherence tomography. Paired comparison was done using Wilcoxon signed-rank test calculator.

Results

Fifty-three eyes of 48 subjects (33 naïve eyes) received intravitreal ziv-aflibercept and were followed between 12 and 30 months following TAE included neovascular age-related macular degeneration (nAMD) (35 eyes) and diabetic macular oedema (DMO) (18 eyes). In eyes with nAMD, CMT decreased by 107.8 µm at the 30-month follow-up (p=0.012) with BCVA gain of 0.52 (p=0.001). In eyes with DMO, CMT decreased by 224.3 µm at the 30-month follow-up (p=0.027) with BCVA gain of 0.46 (p=0.042). Combining all disease categories, the mean number of injections was 9.2 at month 12, 2.5 between 12 and 18 months, 1.6 between 18 and 24 months and 1.0 between 24 and 30 months.

Conclusions

Using TAE regimen, intravitreal ziv-aflibercept appeared efficacious at managing retinal disease through month 30 using the TAE regimen.

Two-year outcomes of intravitreal ziv-aflibercept

AIM

To assess the two-year outcome of intravitreal ziv-aflibercept (IVZ) in eyes with macular diseases.

METHODS

Consecutive subjects with various macular diseases that received six or more of 0.05 mL IVZ (1.25 mg) injections with at least 1 year follow-up were included. Outcome measures were best-corrected visual acuity (BCVA) (logarithm of the minimum angle of resolution) and central macular thickness (CMT) on spectral domain optical coherence tomography. Paired comparison was done using Wilcoxon signed-rank test calculator.

RESULTS

107 eyes of 91 subjects received IVZ and were followed with mean±SD follow-up interval of 1.48±0.44 months following treat and extend or pro-re-nata protocol. The distribution included neovascular macular degeneration (42 eyes), diabetic macular oedema (32 eyes) and macular oedema secondary to retinal vein occlusion (11 eyes). Fifty eyes were naive, while 57 eyes were previously treated. Combining all disease categories, CMT decreased significantly by 133.0±153.0 µm at the 24-month follow-up (P<0.001) with BCVA gain of 0.35±0.37 at the 24-month follow-up (P<0.001) with mean number of injections of 8.5 at month 12, 2.4 between 12 and 18 month and 1.7 between 18 and 24 month. Ocular and systemic adverse effects included one episode of transient uveitis and one instance of central retinal artery occlusion after 1121 injections.

CONCLUSIONS

IVZ appears safe and efficacious in the therapy of macular diseases through 2 years.

One-year outcomes of ziv-aflibercept for macular edema in central retinal vein occlusion

Purpose

To report the 12-month efficacy and safety outcomes of intravitreal ziv-aflibercept in macular edema secondary to central retinal vein occlusion (CRVO).

Methods

Interventional case series documenting 12-month outcomes of intravitreal ziv-aflibercept (1.25 mg in 0.05 mL) in 6 patients with treatment-naive macular edema secondary to CRVO. All patients had comprehensive ophthalmic examination, spectral domain optical coherence tomography at baseline and all follow-up visits, and fluorescein. Retreatment decisions were based on recurrence or persistence of intraretinal or subretinal fluid, deterioration in visual acuity (VA), increase in central subfield thickness (CST) by ≥ 50 μm from the previous visit, or lowest recorded CST.

Results

Participants had (2 males, 4 females) an average age of 53.5 years. From baseline to 12 months, the mean logMAR VA improved from 0.86 (Snellen ≈ 20/145) to 0.33 (Snellen ≈ 20/40), central macular thickness decreased from 519 μm to 255 μm, and total macular volume decreased from 14.7 mm³ to 7.1 mm³. No eyes had uveitis, cataract progression, intraocular pressure (IOP) elevations, or systemic adverse events.

Conclusions and importance

Ziv-aflibercept achieves favorable intermediate-term functional and structural outcomes in macular edema secondary to CRVO. No safety concerns were raised. Low-cost ziv-aflibercept may thus be useful for CRVO in resource-poor countries. Further prospective studies in larger cohorts are needed further establish the efficacy and safety of this agent.

Retinal and choroidal angiogenesis: a review of new targets

Retinal and choroidal neovascularization are a major cause of significant visual impairment, worldwide. Understanding the various factors involved in the accompanying physiopathology is vital for development of novel treatments, and most important, for preserving patient vision. The intraocular use of anti-vascular endothelial growth factor therapeutics has improved management of the retinal and choroidal neovascularization but some patients do not respond, suggesting other vascular mediators may also contribute to ocular angiogenesis. Several recent studies examined possible new targets for future anti-angiogenic therapies. Potential targets of retinal and choroidal neovascularization therapy include members of the platelet-derived growth factor family, vascular endothelial growth factor sub-family, epidermal growth factor family, fibroblast growth factor family, transforming growth factor-β superfamily (TGF-β1, activins, follistatin and bone morphogenetic proteins), angiopoietin-like family, galectins family, integrin superfamily, as well as pigment epithelium derived factor, hepatocyte growth factor, angiopoietins, endothelins, hypoxia-inducible factors, insulin-like growth factors, cytokines, matrix metalloproteinases and their inhibitors and glycosylation proteins. This review highlights current antiangiogenic therapies under development, and discusses future retinal and choroidal pro- and anti-angiogenic targets as wells as the importance of developing of new drugs.

The complexities underlying age-related macular degeneration: could amyloid beta play an important role?

Age-related macular degeneration (AMD) causes irreversible loss of central vision for which there is no effective treatment. Incipient pathology is thought to occur in the retina for many years before AMD manifests from midlife onwards to affect a large proportion of the elderly. Although genetic as well as non-genetic/environmental risks are recognized, its complex aetiology makes it difficult to identify susceptibility, or indeed what type of AMD develops or how quickly it progresses in different individuals. Here we summarize the literature describing how the Alzheimer's-linked amyloid beta (Aβ) group of misfolding proteins accumulate in the retina. The discovery of this key driver of Alzheimer's disease in the senescent retina was unexpected and surprising, enabling an altogether different perspective of AMD. We argue that Aβ fundamentally differs from other substances which accumulate in the ageing retina, and discuss our latest findings from a mouse model in which physiological amounts of Aβ were subretinally-injected to recapitulate salient features of early AMD within a short period. Our discoveries as well as those of others suggest the pattern of Aβ accumulation and pathology in donor aged/AMD tissues are closely reproduced in mice, including late-stage AMD phenotypes, which makes them highly attractive to study dynamic aspects of Aβ-mediated retinopathy. Furthermore, we discuss our findings revealing how Aβ behaves at single-cell resolution, and consider the long-term implications for neuroretinal function. We propose Aβ as a key element in switching to a diseased retinal phenotype, which is now being used as a biomarker for late-stage AMD.