Electrophysiology-Guided Genetic Characterisation Maximises Molecular Diagnosis in an Irish Paediatric Inherited Retinal Degeneration Population.

Inherited retinal degenerations (IRDs) account for over one third of the underlying causes of blindness in the paediatric population. Patients with IRDs often experience long delays prior to reaching a definitive diagnosis. Children attending a tertiary care paediatric ophthalmology department with phenotypic (i.e., clinical and/or electrophysiologic) evidence suggestive of IRD were contacted for genetic testing during the SARS-CoV-2-19 pandemic using a "telegenetics" approach. Genetic testing approach was panel-based next generation sequencing (351 genes) via a commercial laboratory (Blueprint Genetics, Helsinki, Finland). Of 70 patient samples from 57 pedigrees undergoing genetic testing, a causative genetic variant(s) was detected for 60 patients (85.7%) from 47 (82.5%) pedigrees. Of the 60 genetically resolved IRD patients, 5% (n = 3) are eligible for approved therapies (RPE65) and 38.3% (n = 23) are eligible for clinical trial-based gene therapies including CEP290 (n = 2), CNGA3 (n = 3), CNGB3 (n = 6), RPGR (n = 5) and RS1 (n = 7). The early introduction of genetic testing in the diagnostic/care pathway for children with IRDs is critical for genetic counselling of these families prior to upcoming gene therapy trials. Herein, we describe the pathway used, the clinical and genetic findings, and the therapeutic implications of the first systematic coordinated round of genetic testing of a paediatric IRD cohort in Ireland.

Irish National Diabetic RetinaScreen Programme: report on five rounds of retinopathy screening and screen-positive referrals. (INDEAR study report no. 1).

OBJECTIVE: To study the uptake of annual diabetic retinopathy screening and study the 5-year trends in the detection of screen-positive diabetic retinopathy and non-diabetes-related eye disease in a cohort of annually screened individuals. DESIGN: Retrospective retinopathy screening attendance and retinopathy grading analysis. SETTING: Community-based retinopathy screening centres for the Diabetic RetinaScreen Programme. PARTICIPANTS: 171 557 were identified by the screening programme to be eligible for annual diabetic retinopathy screening. 120 048 individuals over the age of 12 consented to and attended at least one screening appointment between February 2013 to December 2018. MAIN OUTCOME MEASURES: Detection rate per 100 000 of any retinopathy, screen-positive referrable retinopathy and nondiabetic eye disease. RESULTS: Uptake of screening had reached 67.2% in the fifth round of screening. Detection rate of screen-positive retinopathy reduced from 13 229 to 4237 per 100 000 screened over five rounds. Detection of proliferative disease had reduced from 2898 to 713 per 100 000 screened. Non-diabetic eye disease detection and referral to treatment centres increased almost eightfold from 393 in round 1 to 3225 per 100 000 screened. The majority of individuals referred to treatment centres for ophthalmologist assessment are over the age of 50 years. CONCLUSIONS: Screening programme has seen a reduced detection rate both screen-positive retinopathy referral in Ireland over five rounds of screening. Management of nondiabetic eye diseases poses a significant challenge in improving visual outcomes of people living with diabetes in Ireland.

Factors associated with non-attendance in the Irish national diabetic retinopathy screening programme (INDEAR study report no. 2).

AIMS: We aimed to determine the patient and screening-level factors that are associated with non-attendance in the Irish National Diabetic Retinal screening programme (Diabetic RetinaScreen). To accomplish this, we modelled a selection of predictors derived from the historical screening records of patients with diabetes. METHODS: In this cohort study, appointment data from the national diabetic retinopathy screening programme (RetinaScreen) were extracted and augmented using publicly available meteorological and geospatial data. A total of 653,969 appointments from 158,655 patients were included for analysis. Mixed-effects models (univariable and multivariable) were used to estimate the influence of several variables on non-attendance to screening appointments. RESULTS: All variables considered for analysis were statistically significant. Variables of note, with meaningful effect, were age (OR: 1.23 per decade away from 70; 95% CI: [1.22-1.24]), type 2 diabetes (OR: 1.10; 95% CI: [1.06-1.14]) and socio-economic deprivation (OR: 1.12; 95% CI: [1.09-1.16]). A majority (52%) of missed appointments were from patients who had missed three or more appointments. CONCLUSIONS: This study is the first to outline factors that are associated with non-attendance within the Irish national diabetic retinopathy screening service. In particular, when corrected for age and other factors, patients with type 2 diabetes had higher rates of non-attendance. Additionally, this is the first study of any diabetic screening programme to demonstrate that weather may influence attendance. This research provides unique insight to guide the implementation of an optimal and cost-effective intervention strategy to improve attendance.

Rhegmatogenous retinal detachments: primary reattachment rates and visual outcomes over a 4-year period.

BACKGROUND AND AIMS: To describe rhegmatogenous retinal detachment surgery in a Dublin tertiary referral centre over a 4-year period and to examine factors predictive of surgical and anatomical success. METHODS: A retrospective study was performed by reviewing the surgical log and the charts of patients who underwent a primary retinal detachment repair in a specialist centre over a 4-year period between 2012 and 2015. We excluded exudative and tractional cases. Multiple parameters were recorded including macular status, visual acuity, type of procedure, complications and visual and anatomical outcomes at 6 months post operation. Primary reattachment rate was calculated alongside change in visual acuity. Chi-square testing and analysis of variance were utilized to determine the effect which lens status, macular status, extent of breaks and type of procedure had on outcome and visual success. RESULTS: A total of 613 primary rhegmatogenous retinal detachment repairs were performed over the 4-year period. Our primary reattachment rate was calculated to be 88.58% (annual range 85.25-91.30%) with a perioperative complication rate of 2.94%. We noted a statistical significant improvement in VA with a median logMAR VA of 1.0 at presentation to 0.5 at 6 months post procedure. Macular status (chi-square test p = 0.15, X2 = 2.072) and lens status (chi-square test p = 0.2974, X2 = 1.086) had no statistical effect on the final anatomical outcome. However, eyes with giant retinal tears were more likely to redetach than those without (chi-square test p = 0.0069, X2 = 7.3). There was no statistical significant difference in the proportion of eyes achieving visual success by surgery category (one-way ANOVA analysis p = 0.501). CONCLUSIONS: This is the first study of its kind in Ireland and will help surgeons benchmark their results against international standards in the future. Accurate recording of logMAR acuity and intraoperative complications is imperative to assist with prospective studies.

DFPE, partially fluorinated ether: a novel approach for experimental intravitreal tamponade.

PURPOSE: To evaluate decafluoro-di-n-pentyl ether (DFPE) as a vitreous tamponade by examining ocular tolerance in rabbits' eyes. METHODS: Thirteen rabbits were divided into 4 groups after mechanical vitrectomy and were followed up to 12 months. The tamponade remained in the eye for 6 months in group 1 (DFPE) and Group 3 (DFPE and silicone oil) and for 12 months in group 2 (DFPE). Group 4 served as control. RESULTS: In groups 1, 2, and 3, dispersion of the fluid appeared 2 weeks postoperatively. Posterior subcapsular cataracts appeared in rabbits' eyes with large fills of DFPE (>50%). Histologic findings in groups 1 and 2 showed no detectable change in outer nuclear layer thickness. Except for some vacuolations, the inner retina was well preserved in all injected rabbits' eyes. On the electroretinography of injected rabbits' eyes, there was no effect on the a wave amplitude and b wave implicit time, but the b wave amplitude was elevated with statistical significance (P < 0.001) at 1, 3, and 6 months postoperatively but with no statistical significance (P > 0.05) after that period when compared with group 4 and unoperated fellow rabbits' eyes of each group. CONCLUSION: Decafluoro-di-n-pentyl ether demonstrated minimum adverse effects in retinal rabbits; further studies are needed before clinical use as short-term tamponade.

Maintenance of perioperative antiplatelet and anticoagulant therapy for vitreoretinal surgery.

BACKGROUND: The objective of this study was to prospectively assess the risk of bleeding from vitreoretinal surgery in a continuous unbiased cohort of patients taking unsuspended antiplatelet or anticoagulant therapy. DESIGN: Prospective hospital-based study. PARTICIPANTS: Eighty-five patients taking unsuspended aspirin, clopidogrel and/or warfarin therapy undergoing all forms of vitreoretinal surgery at The Mater Misericordiae University and The Mater Private Hospital, Dublin, Ireland. METHODS: Consecutive patients undergoing vitreoretinal surgery taking unsuspended antiplatelet or anticoagulant therapy over a 1-year period were included in this prospective study to evaluate the intraoperative and postoperative bleeding complications. MAIN OUTCOME MEASURES: The intraoperative and postoperative bleeding rates. RESULTS: One hundred and seven vitreoretinal procedures were performed on 85 patients taking unsuspended antiplatelet or anticoagulant therapy. The intraoperative bleeding rate was 23%, the majority of which consisted of mild bleeding into the vitreous cavity during vitrectomy. The postoperative bleeding rate was 22%, consisting of 3.7% anterior chamber haemorrhage, 11% dispersed vitreous cavity haemorrhage, 4.7% dense vitreous cavity haemorrhage, 0.9% subretinal haemorrhage and 1.9% localized choroidal haemorrhage. The single greatest significant independent predictor of intraoperative bleeding was proliferative diabetic retinopathy and of postoperative bleeding was the presence of diabetes mellitus. CONCLUSIONS: There were no cases of uncontrolled intraoperative haemorrhage or serious postoperative choroidal haemorrhage. Mild haemorrhagic oozing during vitrectomy and dispersed vitreous cavity haemorrhage postoperatively were common. For the majority of patients taking antiplatelet or anticoagulant medication, these agents can be safely continued in the vitreoretinal surgical perioperative period.

MIO-M1 cells and similar muller glial cell lines derived from adult human retina exhibit neural stem cell characteristics.

Growing evidence suggests that glial cells may have a role as neural precursors in the adult central nervous system. Although it has been shown that Müller cells exhibit progenitor characteristics in the postnatal chick and rat retinae, their progenitor-like role in developed human retina is unknown. We first reported the Müller glial characteristics of the spontaneously immortalized human cell line MIO-M1, but recently we have derived similar cell lines from the neural retina of several adult eye donors. Since immortalization is one of the main properties of stem cells, we investigated whether these cells expressed stem cell markers. Cells were grown as adherent monolayers, responded to epidermal growth factor, and could be expanded indefinitely without growth factors under normal culture conditions. They could be frozen and thawed without losing their characteristics. In the presence of extracellular matrix and fibroblast growth factor-2 or retinoic acid, they acquired neural morphology, formed neurospheres, and expressed neural stem cell markers including betaIII tubulin, Sox2, Pax6, Chx10, and Notch 1. They also expressed markers of postmitotic retinal neurons, including peripherin, recoverin, calretinin, S-opsin, and Brn3. When grafted into the subretinal space of dystrophic Royal College of Surgeons rats or neonatal Lister hooded rats, immortalized cells migrated into the retina, where they expressed various markers of retinal neurons. These observations indicate that adult human neural retina harbors a population of cells that express both Müller glial and stem cell markers and suggest that these cells may have potential use for cell-based therapies to restore retinal function. Disclosure of potential conflicts of interest is found at the end of this article.

Transplantation of Schwann cell line clones secreting GDNF or BDNF into the retinas of dystrophic Royal College of Surgeons rats.

PURPOSE: To assess the capacity of a retrovirus-engineered Schwann cell line (SCTM41), transfected with either a glial cell line-derived neurotrophic factor (GDNF) construct or a brain-derived neurotrophic factor (BDNF) construct, to sustain visual function in the dystrophic Royal College of Surgeons (RCS) rat. METHODS: Cell suspensions were injected into the subretinal space of the right eye of 3-week-old dystrophic RCS rats through a transscleral approach. The left eye remained as an unoperated control. Sham-surgery animals received injections of carrier medium plus DNase to the right eye. All animals were placed on oral cyclosporine. At 8, 12, 16, and 20 weeks of age, animals were placed in a head-tracking apparatus and screened for their ability to track square-wave gratings at various spatial frequencies (0.125, 0.25, and 0.5 cyc/deg). At the end of the experiment, the animals were perfused and processed for histologic assessment of photoreceptor survival. RESULTS: Animals with SCTM41-GDNF-secreting cells, on average, head tracked longer than animals with SCTM41-BDNF-secreting cells, and both performed better than those injected with the parent SCTM41 line. All tracked longer than sham-surgery or nonsurgical dystrophic eyes. Each cell type demonstrated preservation of photoreceptors up to at least 4 months of age, over and above the sham-surgery control. CONCLUSIONS: Engineered Schwann cells sustain retinal structure and function in the dystrophic RCS rat. Cells overexpressing GDNF or BDNF had a greater effect on photoreceptor survival than the parent line or sham surgery. This study demonstrates that ex vivo gene therapy and subsequent cell transplantation can be effective in preserving photoreceptors from the cell death that normally accompanies retinal degeneration.

Transplantation of syngeneic Schwann cells to the retina of the rhodopsin knockout (rho(-/-)) mouse.

PURPOSE: To determine whether subretinal Schwann cell transplantation can prolong the survival of photoreceptors in the rhodopsin knockout (rho(-/-)) mouse. METHODS: Schwann cells were prepared from postnatal day (PN) 5 to 7 mouse pups and grafted subretinally into the eyes of PN35 rho(-/-) mice. RT-PCR was performed on similarly prepared cells to determine growth factor production in vitro. Eyes were retrieved at PN70 for anatomic and statistical analysis. Control animals received grafts of fibroblasts or sham surgery. RESULTS: RT-PCR demonstrated the presence of message for ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF), and glia-derived neurotrophic factor (GDNF) in the cultured Schwann cells. Schwann cell grafts produced a statistically significant rescue of photoreceptors in a restricted area of retina at PN70, but the effect was lost by PN140. Preserved inner segments could be identified, but outer segments were never present. Sham surgery also resulted in photoreceptor rescue but at a reduced level. Fibroblast grafts appeared to produce little or no rescue effect. Grafts of Schwann cells or fibroblasts and sham surgery induced a reactive Müller glial response. CONCLUSIONS: Schwann cells can prolong photoreceptor survival in the rhodopsin knockout mouse until at least PN70.