PRPF31-retinitis pigmentosa: Challenges and opportunities for clinical translation.

Mutations in pre-mRNA processing factor 31 cause autosomal dominant retinitis pigmentosa (PRPF31-RP), for which there is currently no efficient treatment, making this disease a prime target for the development of novel therapeutic strategies. PRPF31-RP exhibits incomplete penetrance due to haploinsufficiency, in which reduced levels of gene expression from the mutated allele result in disease. A variety of model systems have been used in the investigation of disease etiology and therapy development. In this review, we discuss recent advances in both in vivo and in vitro model systems, evaluating their advantages and limitations in the context of therapy development for PRPF31-RP. Additionally, we describe the latest approaches for treatment, including AAV-mediated gene augmentation, genome editing, and late-stage therapies such as optogenetics, cell transplantation, and retinal prostheses.

Survival of Neural Progenitors Derived from Human Embryonic Stem Cells Following Subretinal Transplantation in Rodents.

Purpose: To examine the survival of neural progenitors (NPs) cells derived from human embryonic stem cells (hESCs) following subretinal (SR) transplantation in rodents. Methods: hESCs engineered to express enhanced green fluorescent protein (eGFP) were differentiated in vitro toward an NP fate using a 4-week protocol. State of differentiation was characterized by quantitative-PCR. NPs in suspension (75,000/µl) were transplanted to the SR-space of Royal College of Surgeons (RCS) rats (n = 66), nude-RCS rats (n = 18), and NOD scid gamma (NSG) mice (n = 53). Success of engraftment was determined at 4 weeks post-transplant by in vivo visualization of GFP-expression using a properly filtered rodent fundus camera. Transplanted eyes were examined in vivo at set time points using the fundus camera, and in select cases, by optical coherence tomography imaging, and after enucleation, by retinal histology and immunohistochemistry. Results: In RCS rats, cell rejection was observed in 29% of eyes at 6 weeks, rising to 92% at 8 weeks. In the more immunodeficient nude-RCS rats, the rejection rate was still high reaching 62% of eyes at 6 weeks post-transplant. Following transplantation in highly immunodeficient NSG mice, survival of the hESC-derived NPs was much improved, with 100% survival at 9 weeks and 72% at 20 weeks. A small number of eyes that were followed past 20 weeks showed survival also at 22 weeks. Conclusions: Immune status of recipient animals influences transplant survival. Highly immunodeficient NSG mice provide a better model for studying long-term survival, differentiation, and possible integration of hESC-derived NPs. Clinical Trial Registration numbers: NCT02286089, NCT05626114.

Retinal Degeneration Associated With RPGRIP1: A Review of Natural History, Mutation Spectrum, and Genotype-Phenotype Correlation in 228 Patients.

Purpose: RPGRIP1 encodes a ciliary protein expressed in the photoreceptor connecting cilium. Mutations in this gene cause ∼5% of Leber congenital amaurosis (LCA) worldwide, but are also associated with cone-rod dystrophy (CRD) and retinitis pigmentosa (RP) phenotypes. Our purpose was to clinically characterize RPGRIP1 patients from our cohort, collect clinical data of additional RPGRIP1 patients reported previously in the literature, identify common clinical features, and seek genotype-phenotype correlations. Methods: Clinical data were collected from 16 patients of our cohort and 212 previously reported RPGRIP1 patients and included (when available) family history, best corrected visual acuity (BCVA), refraction, comprehensive ocular examination, optical coherence tomography (OCT) imaging, visual fields (VF), and full-field electroretinography (ffERG). Results: Out of 228 patients, the majority (197, 86%) were diagnosed with LCA, 18 (7%) with RP, and 13 (5%) with CRD. Age of onset was during early childhood (n = 133, average of 1.7 years). All patients but 6 had moderate hyperopia (n = 59, mean of 4.8D), and average BCVA was 0.06 Snellen (n = 124; only 10 patients had visual acuity [VA] > 0.10 Snellen). On funduscopy, narrowing of blood vessels was noted early in life. Most patients had mild bone spicule-like pigmentation starting in the midperiphery and later encroaching upon the posterior pole. OCT showed thinning of the outer nuclear layer (ONL), while cystoid changes and edema were relatively rare. VF were usually very constricted from early on. ffERG responses were non-detectable in the vast majority of cases. Most of the mutations are predicted to be null (363 alleles), and 93 alleles harbored missense mutations. Missense mutations were identified only in two regions: the RPGR-interacting domain and the C2 domains. Biallelic null mutations are mostly associated with a severe form of the disease, whereas biallelic missense mutations usually cause a milder disease (mostly CRD). Conclusion: Our results indicate that RPGRIP1 biallelic mutations usually cause severe retinal degeneration at an early age with a cone-rod pattern. However, most of the patients exhibit preservation of some (usually low) BCVA for a long period and can potentially benefit from gene therapy. Missense changes appear only in the conserved domains and are associated with a milder phenotype.

A deep intronic substitution in CNGB3 is one of the major causes of achromatopsia among Jewish patients.

Purpose: Although most (or even all) genes that can cause achromatopsia (ACHM) when mutated are known, some patients are still negative for mutations even after screening the coding sequence of all known genes. Our aim was to characterize the genetic and clinical aspects of a deep intronic (c.1663-1205G>A, IVS14-1205G>A) CNGB3 variant. Methods: Clinical evaluation included visual acuity testing, refractive error, a full clinical eye exam, full-field electroretinography (ffERG), color vision testing, and retinal imaging. Genetic analysis of CNGB3 exons, as well as part of intron 14, was performed by Sanger sequencing of PCR products. Results: Screening for the CNGB3 c.1663-1205G>A variant revealed 17 patients belonging to 12 unrelated families who were either homozygous for this variant (7 cases, 5 families) or heterozygous in combination with another heterozygous known CNGB3 mutation (10 cases, 7 families). All patients were diagnosed with cone-dominated disease, mainly complete ACHM. In all cases, the disease had an early, congenital onset. Visual acuity was markedly impaired, ranging between 0.07 and 0.32 on the Early Treatment Diabetic Retinopathy Study (ETDRS) scale (logarithm of the minimum angle of resolution [LogMAR] +1.18 to +0.50), with a mean visual acuity of 0.15 ETDRS (LogMAR +0.80). Additional typical signs of ACHM, including impaired color vision, light aversion, and nystagmus, were also noted in all patients. As is common in ACHM, fundus exams were largely unremarkable in most patients, with mild foveal RPE changes seen in some cases at older ages. ERG was available for 14 out of 17 patients, and in all of them-including infants from the age of 6 months-cone responses were nondetectable. In a few cases, rod involvement was also evident, with a mild reduction of amplitudes. Optical coherence tomography (OCT) imaging showed irregularity of the ellipsoid zone in the foveal area in some patients. Conclusions: CNGB3 is the most common cause of ACHM in patients of European descent; this is mainly due to a panethnic founder mutation, c.1148del. Here, we report on an intronic CNGB3 variant that is more frequent than the c.1148del mutation in our cohort of Jewish patients. Among our ACHM cohort, 63.7% of patients had biallelic CNGA3 mutations and 26.4% had biallelic CNGB3 mutations. The phenotype of patients harboring the intronic mutation falls largely within the spectrum commonly seen in ACHM. Since gene therapy for CNGB3 is currently under investigation, these patients might benefit from this promising therapy. Given that this variant is not detectable by current commonly used genetic testing platforms, these patients could easily be missed.

Postoperative Macular Proliferative Vitreoretinopathy: A Case Series and Literature Review.

Premacular membranes developing following pars plana vitrectomy (PPV) can cause significant anatomical and functional deficits to the macula. Recent reports showed that postoperative premacular membranes are a localized presentation of macular proliferative vitreoretinopathy (mPVR). Here, we report retrospectively a case series of 5 patients with severe mPVR which developed following uneventful PPV and were followed up to 32 months in the Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, between October 2016 and February 2020. All patients underwent primary repair of rhegmatogenous retinal detachment (RRD) before mPVR developed. Mean best-corrected visual acuity (BCVA) at presentation was 20/76 Snellen (0.58 LogMAR). Median duration of the retinal detachment time until surgery was 1.5 days (range 1-21 days). Mean interval time from last normal follow-up exam to diagnosis of mPVR was 19 days (range 10-28). BCVA dropped from a mean of 20/38 Snellen (0.28 LogMAR) prior to mPVR development to 20/166 Snellen (0.92 LogMAR) following its development, recovering to 20/57 Snellen (0.45 LogMAR) after peeling of membranes. Mean central macular thickness measured by optical coherence tomography decreased from 711 to 354 µm postsurgery. In conclusion, short-term mPVR is a different entity from macular pucker in terms of rapid development, structural distortion, and visual compromise. Surgical treatment significantly restores macular function and anatomy.

Hybrid Telehealth Medical Retina Clinic Due to Provider Exposure and Quarantine During COVID-19 Pandemic.

OBJECTIVE: To present our hybrid telehealth medical retina clinic service with intravitreal injections (IVI) treatment as a safe alternative to in-person visits and examination during COVID-19 pandemic disease. METHODS: Due to exposure to a COVID-19 positive retina fellow, our retina service, in quarantine, evaluated patients' medical files and retinal scans using a telemedicine approach. A different protocol for patients coming for IVI during the COVID-19 pandemic was established for IVI administration. RESULTS: During the 14-day quarantine period (between March 18th and March 31st 2020), the hybrid telehealth medical retina clinic performed 523 IVI to 394 patients with a mean age ± SD 70.96 ± 14.4 years. IVI were administered for neovascular age-related macular degeneration in 50.5% of the cases (199 patients), diabetic macular edema in 21.3% (84 patients), retinal vein occlusion in 17.5% (69 patients), and 10.7% for other retinal pathologies (42 patients). No ocular or systemic complications were observed. CONCLUSION: During disasters and pandemics, IVI can be provided safely using a hybrid telehealth medical retina clinic approach but only in the appropriate patient and health care system.

Ophthalmology practice during the COVID-19 pandemic.

OBJECTIVE: To present an established practice protocol for safe and effective hospital-setting ophthalmic practice during the coronavirus disease 2019 (COVID-19) pandemic. METHODS AND ANALYSIS: Literature was reviewed to identify articles relevant to COVID-19 pandemic and ophthalmology. The following keywords were used: COVID-19, SARS-CoV-2 and telemedicine, combined with eye, ophthalmology, conjunctivitis and tears. Data were extracted from the identified manuscripts and discussed among subspecialists to obtain consensus evidence-based practice. RESULTS: A protocol for ophthalmic practice in the era of COVID-19 pandemic was established. The protocol covered patient screening, clinic flow, required personal protective equipment and modifications of ophthalmic equipment for improved safety. CONCLUSION: Important literature emerged with respect to the practice of ophthalmology in the era of COVID-19. An evidence-based ophthalmic practice protocol was established and should be modified in the future to accommodate new insights on the COVID-19 pandemic.