Estimating the rate of severe visual loss (wipe-out) following cataract surgery, a British Ophthalmological Surveillance Unit (BOSU) study.

BACKGROUND: A sudden, irreversible reduction in visual acuity ('wipe-out') is a feared complication of cataract surgery. Current literature on wipe-out is limited in quantity and quality, and largely predates modern cataract surgery and imaging techniques. The objectives of our study were to estimate the incidence of wipe-out and to identify potential risk factors. METHODS: We prospectively collated cases of wipe-out occurring in the UK during a 25-month study period using the British Ophthalmic Surveillance Unit reporting system. A total of 21 potential cases of wipe-out were reported, 5 of which met all inclusion and exclusion criteria. RESULTS: The estimated incidence of wipe-out during the study period was 0.00000298, or approximately 3 cases per million cataract operations. All cases of wipe-out occurred exclusively in patients with advanced glaucoma (mean deviation -21.0 decibels or worse in the operated eye), with an over-representation of black people (40%) in our case series. A prior diagnosis of retinal vein occlusion (60%) and elevated post-operative IOP (40%) were more common among individuals suffering from wipe-out compared to the general population, suggesting these factors may contribute to the pathogenesis of wipe-out. CONCLUSIONS: Our study shows that wipe-out is a rare complication, affecting approximately 3 per million undergoing cataract surgery. Patients with advanced glaucoma, black patients, and those with previous retinal vein occlusions may be at greater risk of wipe-out. We hope that the findings of our study will be used to help inform treatment decision-making and the cataract surgery consent process.

Spatiotemporal control of actomyosin contractility by MRCKß signaling drives phagocytosis.

Phagocytosis requires actin dynamics, but whether actomyosin contractility plays a role in this morphodynamic process is unclear. Here, we show that in the retinal pigment epithelium (RPE), particle binding to Mer Tyrosine Kinase (MerTK), a widely expressed phagocytic receptor, stimulates phosphorylation of the Cdc42 GEF Dbl3, triggering activation of MRCKß/myosin-II and its coeffector N-WASP, membrane deformation, and cup formation. Continued MRCKß/myosin-II activity then drives recruitment of a mechanosensing bridge, enabling cytoskeletal force transmission, cup closure, and particle internalization. In vivo, MRCKß is essential for RPE phagocytosis and retinal integrity. MerTK-independent activation of MRCKß signaling by a phosphomimetic Dbl3 mutant rescues phagocytosis in retinitis pigmentosa RPE cells lacking functional MerTK. MRCKß is also required for efficient particle translocation from the cortex into the cell body in Fc receptor-mediated phagocytosis. Thus, conserved MRCKß signaling at the cortex controls spatiotemporal regulation of actomyosin contractility to guide distinct phases of phagocytosis in the RPE and represents the principle phagocytic effector pathway downstream of MerTK.

Patient generated aerosol in the context of ophthalmic surgery.

OBJECTIVE: To assess the patterns of patient generated aerosol in the context of ophthalmic surgery and ophthalmic examinations. To inform medical teams regarding potential hazards and suggest mitigating measures. METHODS: Qualitatively, real-time time videography assessed exhalation patterns from simulated patients under different clinical scenarios using propylene glycol from an e-cigarette. Quantitatively, high-speed Schlieren imaging was performed to enable high resolution recordings analysable by MATLAB technical computing software. RESULTS: Without a face mask, the standard prior to COVID 19, vapour was observed exiting through the opening in the drape over the surgical field. The amount of vapour increased when a surgical mask was worn. With a taped face mask, the amount of vapour decreased and with inclusion of a continuous suction device, the least amount of vapour was seen. These results were equivocal when the patient was supine or sitting upright. High-speed Schlieren imaging corroborated these findings and in addition showed substantial increase in airflow egress during coughing and with ill-fitting face masks. CONCLUSION: Advising patients to wear a surgical mask at the time of ophthalmic interventions potentially contaminants the ocular field with patient generated aerosol risking endophthalmitis. Surgeon safety can be maintained with personal protective equipment to mitigate the increased egress of vapour from the surgical drape and taping, with or without suction is advisable, whilst meticulous hygiene around lenses is required at the time of slit lamp examination.

Phenotypic and Functional Characterization of Müller Glia Isolated from Induced Pluripotent Stem Cell-Derived Retinal Organoids: Improvement of Retinal Ganglion Cell Function upon Transplantation.

Glaucoma is one of the leading causes of blindness, and there is an ongoing need for new therapies. Recent studies indicate that cell transplantation using Müller glia may be beneficial, but there is a need for novel sources of cells to provide therapeutic benefit. In this study, we have isolated Müller glia from retinal organoids formed by human induced pluripotent stem cells (hiPSCs) in vitro and have shown their ability to partially restore visual function in rats depleted of retinal ganglion cells by NMDA. Based on the present results, we suggest that Müller glia derived from retinal organoids formed by hiPSC may provide an attractive source of cells for human retinal therapies, to prevent and treat vision loss caused by retinal degenerative conditions. Stem Cells Translational Medicine 2019;8:775&784.

Phase 1 clinical study of an embryonic stem cell-derived retinal pigment epithelium patch in age-related macular degeneration.

Age-related macular degeneration (AMD) remains a major cause of blindness, with dysfunction and loss of retinal pigment epithelium (RPE) central to disease progression. We engineered an RPE patch comprising a fully differentiated, human embryonic stem cell (hESC)-derived RPE monolayer on a coated, synthetic basement membrane. We delivered the patch, using a purpose-designed microsurgical tool, into the subretinal space of one eye in each of two patients with severe exudative AMD. Primary endpoints were incidence and severity of adverse events and proportion of subjects with improved best-corrected visual acuity of 15 letters or more. We report successful delivery and survival of the RPE patch by biomicroscopy and optical coherence tomography, and a visual acuity gain of 29 and 21 letters in the two patients, respectively, over 12 months. Only local immunosuppression was used long-term. We also present the preclinical surgical, cell safety and tumorigenicity studies leading to trial approval. This work supports the feasibility and safety of hESC-RPE patch transplantation as a regenerative strategy for AMD.

Stem cell-derived retinal pigment epithelium transplantation for treatment of retinal disease.

Age-related macular degeneration remains the most common cause of blindness in the western world, severely comprising patients' and carers' quality of life and presenting a great cost to the healthcare system. As the disease progresses, the retinal pigmented epithelium (RPE) layer at the back of the eye degenerates, contributing to a series of events resulting in visual impairment. The easy accessibility of the eye has allowed for in-depth study of disease progression in patients, while in vivo studies have facilitated investigations into healthy and diseased RPE. Consequently, a number of research groups are examining different approaches for the replacement of RPE cells in age-related macular degeneration (AMD) patients. This chapter examines some of these initial proof-of-principle studies and goes on to review the use of pluripotent stem cells as a source for RPE replacement in a number of current AMD clinical trials. Finally, we consider just some of the regulatory and manufacturing challenges presented in taking a promising AMD treatment from the research bench into clinical trials in patients, and how to mitigate potential risks early in process development.

Rescue of the MERTK phagocytic defect in a human iPSC disease model using translational read-through inducing drugs.

Inherited retinal dystrophies are an important cause of blindness, for which currently there are no effective treatments. In order to study this heterogeneous group of diseases, adequate disease models are required in order to better understand pathology and to test potential therapies. Induced pluripotent stem cells offer a new way to recapitulate patient specific diseases in vitro, providing an almost limitless amount of material to study. We used fibroblast-derived induced pluripotent stem cells to generate retinal pigment epithelium (RPE) from an individual suffering from retinitis pigmentosa associated with biallelic variants in MERTK. MERTK has an essential role in phagocytosis, one of the major functions of the RPE. The MERTK deficiency in this individual results from a nonsense variant and so the MERTK-RPE cells were subsequently treated with two translational readthrough inducing drugs (G418 & PTC124) to investigate potential restoration of expression of the affected gene and production of a full-length protein. The data show that PTC124 was able to reinstate phagocytosis of labeled photoreceptor outer segments at a reduced, but significant level. These findings represent a confirmation of the usefulness of iPSC derived disease specific models in investigating the pathogenesis and screening potential treatments for these rare blinding disorders.

Using induced pluripotent stem cells to understand retinal ciliopathy disease mechanisms and develop therapies.

The photoreceptor cells in the retina have a highly specialised sensory cilium, the outer segment (OS), which is important for detecting light. Mutations in cilia-related genes often result in retinal degeneration. The ability to reprogramme human cells into induced pluripotent stem cells and then differentiate them into a wide range of different cell types has revolutionised our ability to study human disease. To date, however, the challenge of producing fully differentiated photoreceptors in vitro has limited the application of this technology in studying retinal degeneration. In this review, we will discuss recent advances in stem cell technology and photoreceptor differentiation. In particular, the development of photoreceptors with rudimentary OS that can be used to understand disease mechanisms and as an important model to test potential new therapies for inherited retinal ciliopathies.

Mislocalisation of BEST1 in iPSC-derived retinal pigment epithelial cells from a family with autosomal dominant vitreoretinochoroidopathy (ADVIRC).

Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare, early-onset retinal dystrophy characterised by distinct bands of circumferential pigmentary degeneration in the peripheral retina and developmental eye defects. ADVIRC is caused by mutations in the Bestrophin1 (BEST1) gene, which encodes a transmembrane protein thought to function as an ion channel in the basolateral membrane of retinal pigment epithelial (RPE) cells. Previous studies suggest that the distinct ADVIRC phenotype results from alternative splicing of BEST1 pre-mRNA. Here, we have used induced pluripotent stem cell (iPSC) technology to investigate the effects of an ADVIRC associated BEST1 mutation (c.704T > C, p.V235A) in patient-derived iPSC-RPE. We found no evidence of alternate splicing of the BEST1 transcript in ADVIRC iPSC-RPE, however in patient-derived iPSC-RPE, BEST1 was expressed at the basolateral membrane and the apical membrane. During human eye development we show that BEST1 is expressed more abundantly in peripheral RPE compared to central RPE and is also expressed in cells of the developing retina. These results suggest that higher levels of mislocalised BEST1 expression in the periphery, from an early developmental stage, could provide a mechanism that leads to the distinct clinical phenotype observed in ADVIRC patients.

Identification and Correction of Mechanisms Underlying Inherited Blindness in Human iPSC-Derived Optic Cups.

Leber congenital amaurosis (LCA) is an inherited retinal dystrophy that causes childhood blindness. Photoreceptors are especially sensitive to an intronic mutation in the cilia-related gene CEP290, which causes missplicing and premature termination, but the basis of this sensitivity is unclear. Here, we generated differentiated photoreceptors in three-dimensional optic cups and retinal pigment epithelium (RPE) from iPSCs with this common CEP290 mutation to investigate disease mechanisms and evaluate candidate therapies. iPSCs differentiated normally into RPE and optic cups, despite abnormal CEP290 splicing and cilia defects. The highest levels of aberrant splicing and cilia defects were observed in optic cups, explaining the retinal-specific manifestation of this CEP290 mutation. Treating optic cups with an antisense morpholino effectively blocked aberrant splicing and restored expression of full-length CEP290, restoring normal cilia-based protein trafficking. These results provide a mechanistic understanding of the retina-specific phenotypes in CEP290 LCA patients and potential strategies for therapeutic intervention.

Headache and transient visual loss as the only presenting symptoms of vertebral artery dissection: a case report.

BACKGROUND: Vertebral artery dissection is an important cause of stroke in the young and diagnosis is often challenging as symptoms are varied and subtle. CASE PRESENTATION: A 33-year-old, previously healthy, white male office worker was stretching his neck when he developed sudden left-sided visual loss lasting 5 minutes associated with headache. He had no other neurological symptoms or signs. He was investigated with a computed tomography angiogram, which revealed a left vertebral artery dissection with a right posterior cerebral artery vascular occlusion. CONCLUSIONS: We describe an atypical case of vertebral artery dissection presenting with sudden transient visual disturbance without neurological signs in an otherwise healthy man. This is a rare but potentially fatal condition that can result in thromboembolic infarction. A high index of suspicion is crucial to make an early diagnosis and avoid devastating neurological outcomes.

Using Stem Cells to Model Diseases of the Outer Retina.

Retinal degeneration arises from the loss of photoreceptors or retinal pigment epithelium (RPE). It is one of the leading causes of irreversible blindness worldwide with limited effective treatment options. Generation of induced pluripotent stem cell (IPSC)-derived retinal cells and tissues from individuals with retinal degeneration is a rapidly evolving technology that holds a great potential for its use in disease modelling. IPSCs provide an ideal platform to investigate normal and pathological retinogenesis, but also deliver a valuable source of retinal cell types for drug screening and cell therapy. In this review, we will provide some examples of the ways in which IPSCs have been used to model diseases of the outer retina including retinitis pigmentosa (RP), Usher syndrome (USH), Leber congenital amaurosis (LCA), gyrate atrophy (GA), juvenile neuronal ceroid lipofuscinosis (NCL), Best vitelliform macular dystrophy (BVMD) and age related macular degeneration (AMD).

Neural retinal regeneration with pluripotent stem cells.

Retinal degeneration represents a huge burden of blinding disease, and currently there are no effective treatments that reverse the most common causes of neural retinal degeneration. Stem cell biology has the potential to significantly ease this burden, not only through the development of disease models of retinal degeneration but also in the manufacture of a replacement for the neural retinal tissue. This review summarizes the major advancements in the last decade in the field of neural retinal regeneration with an emphasis on the differentiation of embryonic and induced pluripotent stem cells into cells with retinal and specifically photoreceptor characteristics.

Stem cells in retinal regeneration: past, present and future.

Stem cell therapy for retinal disease is under way, and several clinical trials are currently recruiting. These trials use human embryonic, foetal and umbilical cord tissue-derived stem cells and bone marrow-derived stem cells to treat visual disorders such as age-related macular degeneration, Stargardt's disease and retinitis pigmentosa. Over a decade of analysing the developmental cues involved in retinal generation and stem cell biology, coupled with extensive surgical research, have yielded differing cellular approaches to tackle these retinopathies. Here, we review these various stem cell-based approaches for treating retinal diseases and discuss future directions and challenges for the field.

Development of human embryonic stem cell therapies for age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of vision loss in older adults and ultimately leads to the death of photoreceptor cells in the macular area of the neural retina. Currently, treatments are only available for patients with the wet form of AMD. In this review, we describe recent approaches to develop cell-based therapies for the treatment of AMD. Recent research has focused on replacing the retinal pigment epithelium (RPE), a monolayer of cells vital to photoreceptor cell health. We discuss the various methods used to differentiate and purify RPE from human embryonic stem cells (HESC), and describe the surgical approaches being used to transplant these cells in existing and forthcoming clinical trials.

VEGF polymorphisms are associated with severity of diabetic retinopathy.

PURPOSE: To determine whether single nucleotide polymorphisms (SNPs) in the vascular endothelial growth factor (VEGF) gene are associated with severity of diabetic retinopathy. METHODS: A case-control study was conducted in which 45 individuals with type 1 or 2 diabetes with proliferative diabetic retinopathy (PDR) and 61 individuals with type 1 or 2 diabetes without retinopathy (DWR) were genotyped for 14 SNPs in the VEGF promoter and gene. RESULTS: Three of the promoter SNP genotypes, -160C, -152A (rs13207351), and -116A (rs1570360), showed significant independent associations with PDR, as well as the minihaplotype CAA (P = 0.00017). Two promoter haplotypes were associated with severity of retinopathy: -460C, -417T, -172C, -165C, -160C, -152A, -141A, -116A, +405C was associated with PDR (OR [95% CI] = 29.92 [3.91, 228.78], P = 1.62 x 10(-5)) and -460C, -2417T, -172C, -165C, -160C, -152A, -141A, -116G, +405G was associated with DWR (OR = 0.05 [0.01, 0.35], P = 0.000373). Furthermore, two haplotype-tagged (ht) SNPs, +4618 (rs735286) and +5092 (rs2146323), and five htSNP haplotypes were associated with severity of retinopathy. When the nine promoter/5' untranslated region [UTR] and five htSNP genotypes were combined into a 14-SNP haplotype, a single haplotype, -460C, -417T, -172C, -165C, -160C, -152A, -141A, -116A, +405C, +674T, +4618C, +5092A, +9162C, +9512C was found to be significantly associated with the PDR group (OR = 18.45 [2.35, 144.67], P = 0.00622). CONCLUSIONS: A clear association was demonstrated between VEGF SNPs and severity of diabetic retinopathy. Furthermore, two of the htSNP haplotypes appear to be more generalized markers for angiogenesis, in that these have been found in prior work to be associated with neovascular age-related macular degeneration.

VEGF polymorphisms are associated with neovascular age-related macular degeneration.

Age-related macular degeneration (AMD) is the most common cause of blindness in the elderly. Linkage has been shown to the vascular endothelial growth factor (VEGF) gene and ocular levels of VEGF are raised in individuals with the neovascular form of disease. To examine the role of VEGF further, we conducted a case-control study where 45 individuals with neovascular AMD and 94 age-matched controls were genotyped for 14 single nucleotide polymorphisms (SNPs) in the VEGF promoter and gene. The single SNP +674 CC genotype was significantly associated with AMD (OR=2.40, 95%CI 1.09-5.26, P=0.027). Haplotype analysis of SNPs +674, +4618, +5092, +9162 and +9512 revealed that CTCCT and TCACC were associated with AMD (OR=15.77, 95% CI 1.91-130.24, P=0.0161 and OR=9.95, 95%CI 3.22-30.74, P=0.000053, respectively). The haplotype TCACT was associated with the control group (P=0.0001832). Furthermore, haplotype analysis of promoter SNPs revealed that possession of the -460T, -417T, -172C, -165C, -160C, -152G, -141A, -116A, +405C haplotype was strongly associated with AMD (OR=18.24, 95%CI 2.25-148.25, P=0.0074). This is the most extensive analysis of the VEGF gene in AMD, demonstrating a clear association with the exudative form of disease, thereby creating the possibility for predictive testing. Smoking, high fat intake and hypertension are negative environmental risk factors in AMD, whereas increased consumption of dietary antioxidants can have a protective effect. Identification of those at risk in the population would allow individual counselling with lifestyle advice to reduce the risks of blindness. (Genbank accession nos M63971 and AF437895).