Inherited Retinal Diseases and Retinal Organoids as Preclinical Cell Models for Inherited Retinal Disease Research.

Inherited retinal diseases (IRDs) are a large group of genetically and clinically diverse blinding eye conditions that result in progressive and irreversible photoreceptor degeneration and vision loss. To date, no cures have been found, although strides toward treatments for specific IRDs have been made in recent years. To accelerate treatment discovery, retinal organoids provide an ideal human IRD model. This review aims to give background on the development and importance of retinal organoids for the human-based in vitro study of the retina and human retinogenesis and retinal pathologies. From there, we explore retinal pathologies in the context of IRDs and the current landscape of IRD treatment discovery. We discuss the usefulness of retinal organoids in this context (as a patient-derived cell model for IRDs) to precisely understand the pathogenesis and potential mechanisms behind a specific IRD-causing variant of interest. Finally, we discuss the importance and promise of retinal organoids in treatment discovery for IRDs, now and in the future.

Vitamin A deficiency retinopathy in the setting of celiac disease and liver fibrosis.

PURPOSE: Vitamin A is a lipid-soluble compound that is critical in maintaining phototransduction. Ocular manifestations of hypovitaminosis A may present with anterior segment signs of xeropthalmia, with advanced cases also causing classic retinal and electrophysiologic changes of vitamin A deficiency retinopathy. We present a case of vitamin A deficiency retinopathy, with corresponding retinal imaging and electrophysiology, in an adult patient with celiac disease and liver fibrosis. METHODS: A single case report was conducted in Toronto, Canada. RESULTS: A 77-year-old male with known celiac disease and liver fibrosis presented progressively worsening vision noticed primarily when driving. Vision was 20/50 OD and 20/200 OS. Bitot spots were noted on anterior segment examination. Fundus photography demonstrated bilateral peripheral macular hypopigmentation and far-peripheral granular retinal hypopigmentation with focal yellow dots and hyper-pigmented deposits. Optical coherence tomography (OCT) imaging demonstrated indistinct outer retinal banding with mild outer nuclear layer thinning, focal hyper-reflective deposits, and a thin choroid bilaterally. Full-field electroretinography (ERG) testing demonstrated reduced rod-isolated and combined rod-cone response amplitudes, and multifocal ERG testing demonstrated blunted individual responses throughout the field. The patient was treated with pulse vitamin A therapy. After 6 months of therapy, ERG responses were back within reference range, and the outer retinal changes reversed; visual acuity improved to 20/30 OD and 20/40 OS. CONCLUSION: This case represents the classic findings of vitamin A deficiency retinopathy on fundus examination and electrophysiologic testing secondary to gastrointestinal pathology. Prompt treatment of high dose vitamin A supplementation led to improvement of full-field and multifocal ERG results, as well as reconstitution of outer retinal architecture.

Exploring the diverse clinical and variant spectrum of CEP78-associated syndrome: Novel pathogenic variants identified in a case series.

Dual sensory impairment, commonly referred to as combined hearing and vision loss, can stem from a diverse spectrum of conditions, each presenting with its unique set of clinical characteristics. Our understanding of dual sensory impairment has expanded significantly in the past decade, broadening the scope of genetic differential diagnoses, including genes such as CEP250, ARSG, TUBB4B, CEP78, and ABHD12. A case series including three patients from two families with genetically diagnosed CEP78-associated cone-rod dystrophy was identified. We collected and reviewed their clinical records, imaging data, and genetic testing results. In addition, a comprehensive literature review was conducted on the phenotype and the genetic testing modality employed in all published CEP78 cases through a PubMed search using the keyword "CEP78." A retinal dystrophy panel detected a novel homozygous CEP78 pathogenic variant (c.1447C>T, p.Arg483*) in siblings-Cases 1 and 2-from Family 1. Both teenagers have a clinical diagnosis of cone-rod dystrophy with presumed normal hearing. Case 3 from Family 2, diagnosed with cone-rod dystrophy and early-onset hearing loss, was found to carry a CEP78 pathogenic variant (c.1206-2A>C) and a likely pathogenic variant (c.856_857del, p.Leu286Glyfs*12) also through panel-based genetic testing. Intriguingly, neither of these variants was reported in an affected sibling's clinical whole-exome sequencing (WES) report when performed in 2015. A review of CEP78-related literature unveiled that the initial report linking CEP78 to cone-rod dystrophy and hearing loss was published in September 2016. Any pathogenic variant found in CEP78 before 2016 would have been categorized as a "clearly disruptive variant in a gene of uncertain significance (GUS)" and might not have been reported in the WES report. It is important to acknowledge that our understanding of genotype-phenotype associations is undergoing rapid expansion. It is also crucial to recognize that repeat genetic testing may represent a fundamentally different approach, given the technological advancements not only in the coverage of the sequencing but also in the more comprehensive understanding of genotype-phenotype associations. This case series also enriches the existing CEP78 literature by providing phenotypic details of the youngest case of CEP78-associated retinopathy reported in the literature (Case 2), which expands our perspective on the natural history of disease in this disorder.

Ensemble of deep convolutional neural networks is more accurate and reliable than board-certified ophthalmologists at detecting multiple diseases in retinal fundus photographs.

AIMS: To develop an algorithm to classify multiple retinal pathologies accurately and reliably from fundus photographs and to validate its performance against human experts. METHODS: We trained a deep convolutional ensemble (DCE), an ensemble of five convolutional neural networks (CNNs), to classify retinal fundus photographs into diabetic retinopathy (DR), glaucoma, age-related macular degeneration (AMD) and normal eyes. The CNN architecture was based on the InceptionV3 model, and initial weights were pretrained on the ImageNet dataset. We used 43 055 fundus images from 12 public datasets. Five trained ensembles were then tested on an 'unseen' set of 100 images. Seven board-certified ophthalmologists were asked to classify these test images. RESULTS: Board-certified ophthalmologists achieved a mean accuracy of 72.7% over all classes, while the DCE achieved a mean accuracy of 79.2% (p=0.03). The DCE had a statistically significant higher mean F1-score for DR classification compared with the ophthalmologists (76.8% vs 57.5%; p=0.01) and greater but statistically non-significant mean F1-scores for glaucoma (83.9% vs 75.7%; p=0.10), AMD (85.9% vs 85.2%; p=0.69) and normal eyes (73.0% vs 70.5%; p=0.39). The DCE had a greater mean agreement between accuracy and confident of 81.6% vs 70.3% (p<0.001). DISCUSSION: We developed a deep learning model and found that it could more accurately and reliably classify four categories of fundus images compared with board-certified ophthalmologists. This work provides proof-of-principle that an algorithm is capable of accurate and reliable recognition of multiple retinal diseases using only fundus photographs.

SEVERE MACULAR EDEMA AFTER TRAUMATIC HEAD INJURY: A CASE OF WHIPLASH MACULOPATHY.

PURPOSE: Whiplash or "traumatic" maculopathy is associated with retinal concussion, typically after the rapid acceleration/deceleration experienced in motor vehicle collisions. It has rarely been discussed in the literature, likely given the spontaneous and relatively rapid nature with which the acute macular edema resolves. A focused clinical history around the trauma and characteristic signs and structural features on retinal imaging help to distinguish this condition from other sequelae of concussive retinal injury. We report a case of whiplash maculopathy after a blunt injury to the head, which presented with unilateral and substantial macular edema in the left eye. METHODS: Case report. RESULTS: A 38-year-old man presented with complaint of a central scotoma in his left eye after a blunt trauma to his head. Comprehensive ophthalmological evaluation and retinal imaging with optical coherence tomography confirmed whiplash maculopathy, with acute macular edema in his left eye. Management with observation and close follow-up showed rapid improvement in his visual symptoms over the course of days and improvement in the severity of macular edema. One month after his injury, macular edema had resolved with only mild structural irregularities, the patient's vision had improved, and he was asymptomatic. CONCLUSION: When observing patients with significant macular edema after concussive head injury, whiplash maculopathy should be considered, regardless of a history of motor vehicle collision. The condition can present with significant asymmetry of disease. The diagnosis generally carries a good prognosis for vision; however, there are cases of persistent central visual disturbances.

RP2 X-LINKED RETINITIS PIGMENTOSA CARRIER STATE PRESENTING WITH VASCULAR LEAKAGE AND UNILATERAL MACULAR ATROPHY.

PURPOSE: We describe the unusual clinical presentation of a 33-year-old woman subsequently identified as a carrier of RP2-associated X-linked retinitis pigmentosa. METHODS: Case report. RESULTS: A 33-year-old woman without a known family history of retinal disease presented with unilateral reduced visual acuity and central scotoma in the left eye. Examination showed underlying macular atrophy in the left eye and a bilateral tapetal-like reflex. Full-field electroretinogram was abnormal in the left eye but normal in the right eye. Notable findings on wide-field imaging included bilateral peripheral vascular leakage on fluorescein angiography and a bilaterally symmetric radial pattern of hyperfluorescence on fundus autofluorescence. Genetic testing demonstrated a pathogenic variant in the gene RP2 confirming that she was a carrier of X-linked retinitis pigmentosa. CONCLUSION: We describe clinical features of the carrier state of RP2-XLRP and expand potential findings to include peripheral vascular leakage. This case highlights the importance of awareness of the carrier state, particularly if a family history cannot be provided.

Deep phenotypic characterization of the retinal dystrophy in patients with RNU4ATAC-associated Roifman syndrome.

PURPOSE: To characterize the retinal phenotype in RNU4ATAC-associated Roifman syndrome. METHODS: Ten patients (including 8 males) with molecularly confirmed Roifman syndrome underwent detailed ophthalmologic evaluation including fundus imaging, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (SD-OCT), and electroretinography (ERG). Six patients had follow-up eye exams. All patients also underwent comprehensive examination for features of extra-retinal Roifman syndrome. RESULTS: All patients had biallelic RNU4ATAC variants. Nyctalopia was common (7/10). Visual acuity at presentation ranged from 20/20 to 20/200 (Age Range: 5-41 years). Retinal exam revealed features of generalized retinopathy with mid-peripheral pigment epithelial changes. A para or peri-foveal ring of hyper-autofluorescence was the commonest FAF abnormality noted (6/8). The SD-OCT demonstrated relative preservation of the foveal ellipsoid zone in six cases; associated features included cystoid changes (5/10) and posterior staphyloma (3/10). The ERG was abnormal in all patients; nine showed generalized rod-cone dystrophy, whilst one patient with sectoral retinal involvement only had isolated rod dystrophy (20 years old). On follow-up examination (Mean duration: 8.16 years), progressive loss of visual acuity (2/6), mid-peripheral retinal atrophy (3/6) or shortening of ellipsoid zone width (1/6) were observed. CONCLUSION: This study has characterized the retinal phenotype in RNU4ATAC-associated Roifman syndrome. Retinal involvement is universal, early-onset, and overall, the retinal and FAF features are consistent with rod-cone degeneration that is slowly progressive over time. The sub-foveal retinal ultrastructure is relatively preserved in majority of patients. Phenotypic variability independent of age exists, and more study of allelic- and sex-based determinants of disease severity are necessary.

Full-Thickness Macular Hole Due to Choroidal Neovascularization in the Setting of Pathologic Myopia.

Purpose: To present a case of myopic choroidal neovascularization (CNV) leading to a full-thickness macular hole (MH) in a patient with macular schisis. Methods: A single case was evaluated. Results: A 65-year-old woman presented with myopic staphyloma and foveoschisis in both eyes. One month after the baseline presentation for myopic macular schisis, the patient presented with a paracentral scotoma in the left eye. Examination showed a submacular hemorrhage in the left eye. Optical coherence tomography of the left eye showed subretinal fluid and subretinal hyperreflective material in the fovea, suggestive of exudative myopia, and a small full-thickness MH (diameter 86 µm). After anti-vascular endothelial growth factor injections, the CNV showed interval improvement; however, a larger full-thickness MH (diameter 287 µm) developed in the left eye. Conclusions: A full-thickness MH developed secondary to CNV, leading to foveal dehiscence in an eye with baseline macular schisis.

ATYPICAL PROLIFERATIVE RETINOPATHY AS THE PRESENTING FEATURE OF CHRONIC MYELOID LEUKEMIA IN A PATIENT WITH DIABETES MELLITUS.

PURPOSE: To describe a case of proliferative retinopathy as the presenting manifestation of chronic myeloid leukemia in a patient with poorly controlled diabetes mellitus (DM). Undiagnosed chronic myeloid leukemia in a patient with pre-existing poorly controlled DM is rarely encountered but must be recognized to treat appropriately with systemic chemotherapy. Significant fundus finding overlaps with DM making the recognition of chronic myeloid leukemia challenging. METHODS: Case report. RESULTS: Fundoscopy revealed scattered dot-blot hemorrhages, venous beading, and numerous Roth spots in all quadrants, in both eyes. In the right eye, there was also a vitreous hemorrhage with evidence of neovascularization near the inferior arcade. Intravenous fluorescein angiography showed significant peripheral capillary nonperfusion without evidence of exudation in both eyes. No macular edema was observed on optical coherence tomography. A review of systems and physical examination was negative for constitutional symptoms, lymphadenopathy, organomegaly, and other symptoms. Retinal findings prompted a complete blood count, which revealed significant leukocytosis. A bone marrow biopsy confirmed a diagnosis of chronic myeloid leukemia. Systemic chemotherapy and pan-retinal photocoagulation successfully normalized the leukocyte count and resolved the vitreous hemorrhage and neovascularization. CONCLUSION: The presence of numerous Roth spots in all quadrants, extensive areas of capillary nonperfusion on intravenous fluorescein angiography, and neovascularization in the absence of exudation or macular edema should prompt investigations to rule out hematologic disorders.

Prevalence and predictors for being unscreened for diabetic retinopathy: a population-based study over a decade.

OBJECTIVE: To determine the population-level predictors for being unscreened for diabetic retinopathy (DR) among individuals with diabetes in a developed country. DESIGN: A retrospective population-based repeated-cross-sectional study. PARTICIPANTS: All individuals with diabetes (types 1 and 2) aged ≥20 years in the universal health care system in Ontario were identified in the 2011-2013 and 2017-2019 time periods. METHODS: The Mantel-Haenszel test was used for the relative risk (RR) comparison of subcategories stratified by the 2 cross-sectional time periods. RESULTS: A total of 1 145 645 and 1 346 578 individuals with diabetes were identified in 2011-2013 and 2017-2019, respectively. The proportion of patients unscreened for DR declined very slightly from 35% (n = 405 967) in 2011-2013 to 34% (n = 455 027) in 2017-2019 of the population with diabetes (RR = 0.967; 95% CI, 0.964-0.9693; p < 0.0001). Young adults aged 20-39 years of age had the highest proportion of unscreened patients (62% and 58% in 2011-2013 and 2017-2019, respectively). Additionally, those who had a lower income quintile (RR = 1.039; 95% CI, 1.036-1.044; p < 0.0001), were recent immigrants (RR = 1.286; 95% CI, 1.280-1.293; p < 0.0001), lived in urban areas (RR = 1.149; 95% CI, 1.145-1.154; p < 0.0001), had a mental health history (RR = 1.117; 95% CI, 1.112-1.122; p < 0.0001), or lacked a connection to a primary care provider (RR = 1.656; 95% CI, 1.644-1.668; p < 0.0001) had a higher risk of being unscreened. CONCLUSIONS: This population-based study suggests that over 1 decade, 33% of individuals with diabetes are unscreened for DR, and young age, low income, immigration, residing in a large city, mental health illness, and no primary care access are the main predictors.

Switching between anti-VEGF agents in the management of refractory diabetic macular edema: A systematic review.

Refractory diabetic macular edema (DME) to monthly intravitreal anti-vascular endothelial growth factor (VEGF) monotherapy has a prevalence of approximately 40% in landmark clinical trials. Options for these patients include use of intravitreal steroids, focal laser, or switching to an alternative anti-VEGF agent. We summarize the key conclusions from studies analyzing the efficacy of switching anti-VEGF agents for refractory DME. Twenty-four studies were included in analysis. The most common definitions of refractory in the included studies were a central retinal thickness (CRT) greater than 300µm or a reduction in CRT less than 10% after at least 3-6 prior anti-VEGF injections. Switching to intravitreal aflibercept (IVA) from either intravitreal ranibizumab (IVR) or bevacizumab (IVB) is associated with moderate to significant improvement in central subfield thickness and may be an appropriate choice for patients with refractory DME. The improvement in retinal thickness and edema is typically seen after the first 3 injections of IVA post-switch. Switching to IVR has also demonstrated improvement in CRT at 3-6 months post switch in large sample population studies. Future studies are required to elucidate the ideal time point for a switch in anti-VEGF agent or which patients would benefit from this change.

PREDICTIVE FACTORS OF SPONTANEOUS RELEASE OF VITREOMACULAR TRACTION: A Systematic Review and Meta-Analysis.

PURPOSE: To review predictive factors of spontaneous vitreomacular traction (VMT) release. METHODS: A systematic literature search was performed on Ovid MEDLINE, Embase, and Cochrane Library. Studies comparing spontaneously released VMT to persistent VMT were included. A meta-analysis was performed using a random effects model, and weighted mean difference, risk ratio (RR), and 95% confidence intervals (95% CI) were reported as appropriate. RESULTS: Of a search of 258 studies, 12 studies were included, from which 272 of 934 eyes (29%) underwent spontaneous release. Mean age was 70.0 years, 37.2% of patients were men, and mean follow-up was 22.0 months. Significant predictive factors for spontaneous release were smaller VMT diameter (n = 177; weighted mean difference = -212.48 µm, 95% CI = [-417.36, -7.60], P = 0.04), epiretinal membrane absence (n = 162; RR = 2.17, 95% CI = [1.18, 3.97], P = 0.01), and right eye involvement (n = 76; RR = 2.10, 95% CI = [1.14, 3.88], P = 0.02). Nonsignificant factors were age, initial best-corrected visual acuity, sex, ocular comorbidity, fellow-eye posterior vitreous detachment, previous intravitreal injection, and VMT classification with focal defined as ≤400 µm. Mean release time was 15.3 months (n = 212). Mean best-corrected visual acuity improved from 0.34 ± 0.21 (Snellen 20/44) to 0.20 ± 0.58 logMAR (Snellen 20/32) postrelease (n = 121). CONCLUSION: Smaller VMT diameter, epiretinal membrane absence, and right eye involvement may support spontaneous VMT release. If patients have tolerable symptoms, clinicians may consider observation in patients with these predictive factors.

Novel RCBTB1 variants causing later-onset non-syndromic retinal dystrophy with macular chorioretinal atrophy.

BACKGROUND: Variants in RCBTB1 were recently described to cause a retinal dystrophy with only eight families described to date and a predominant phenotype of macular atrophy and peripheral reticular degeneration. Here, we further evaluate the genotypic and phenotypic characteristics of biallelic RCBTB1-associated retinal dystrophy in a North American clinic population. METHODS: A retrospective analysis of genetic and clinical features was performed in individuals with biallelic variants in RCBTB1. RESULTS: Three unrelated individuals of French-Canadian descent with rare biallelic RCBTB1 variants were identified. All individuals shared a novel p.(Ser342Leu) missense variant; one patient was homozygous whereas the other two each possessed a second unique novel variant p.(Gln120*) and p.(Pro224Leu). All three had macula-predominant disease with symptom onset in the fifth decade of life. CONCLUSION: This report adds to the genetic diversity of RCBTB1-associated disease. These cases confirm the later-onset, relative to many other retinal dystrophies, and macular focus of disease described in most cases to-date. They are thus a reminder of considering hereditary disease in the differential for later-onset macular atrophy.

Spontaneous Closure of an Idiopathic Full-Thickness Macular Hole: A Literature Review.

Purpose: This work reviews the literature regarding spontaneous closure of idiopathic full-thickness macular holes (FTMHs). Methods: Literature on patients with spontaneous idiopathic FTMH closure was reviewed via Ovid MEDLINE, EMBASE, and PubMed through July 16, 2020. A total of 27 of 66 identified articles were included. Results: A total of 68 eyes had spontaneous closure. Of the patients, 62.7% were women and the average age was 67.5 years. Visual acuity improved from Snellen 20/78 to 20/33 post closure. The average hole diameter was 176.8 µm; the largest was 350 µm. Most were stage 2 according to Gass and of small size according to International Vitreomacular Traction Study Group (IVTS) staging. The predominant classification system in recent literature is IVTS staging. The average optical coherence tomography-observed closure time was 4.5 months. Conclusions: On review, reported spontaneous closure rates of all idiopathic FTMH range from 3% to 15%, and no demographic subgroups are more likely to have closure. Holes ≤250 µm have higher closure rates (22.2%) than those in the range of >250 to 400 µm (13.3%) and ≥400 µm (0%). Closure is associated with favorable visual outcomes, and retinal bridging via glial cells is likely critical to closure. These determinations were based on limited numbers; prospective studies are needed to further ascertain rate, mechanism, and characteristics. IVTS staging provides reliable reporting and insight into whether FTMH can be observed before surgery.

Beyond Sector Retinitis Pigmentosa: Expanding the Phenotype and Natural History of the Rhodopsin Gene Codon 106 Mutation (Gly-to-Arg) in Autosomal Dominant Retinitis Pigmentosa.

Sector and pericentral are two rare, regional forms of retinitis pigmentosa (RP). While usually defined as stable or only very slowly progressing, the available literature to support this claim is limited. Additionally, few studies have analyzed the spectrum of disease within a particular genotype. We identified all cases (9 patients) with an autosomal dominant Rhodopsin variant previously associated with sector RP (RHO c.316G > A, p.Gly106Arg) at our institution. Clinical histories were reviewed, and testing included visual fields, multimodal imaging, and electroretinography. Patients demonstrated a broad phenotypic spectrum that spanned regional phenotypes from sector-like to pericentral RP, as well as generalized disease. We also present evidence of significant intrafamilial variability in regional phenotypes. Finally, we present the longest-reported follow-up for a patient with RHO-associated sector-like RP, showing progression from sectoral to pericentral disease over three decades. In the absence of comorbid macular disease, the long-term prognosis for central visual acuity is good. However, we found that significant progression of RHO p.Gly106Arg disease can occur over protracted periods, with impact on peripheral vision. Longitudinal widefield imaging and periodic ERG reassessment are likely to aid in monitoring disease progression.

The Next Generation of Molecular and Cellular Therapeutics for Inherited Retinal Disease.

Inherited retinal degenerations (IRDs) are a diverse group of conditions that are often characterized by the loss of photoreceptors and blindness. Recent innovations in molecular biology and genomics have allowed us to identify the causative defects behind these dystrophies and to design therapeutics that target specific mechanisms of retinal disease. Recently, the FDA approved the first in vivo gene therapy for one of these hereditary blinding conditions. Current clinical trials are exploring new therapies that could provide treatment for a growing number of retinal dystrophies. While the field has had early success with gene augmentation strategies for treating retinal disease based on loss-of-function mutations, many novel approaches hold the promise of offering therapies that span the full spectrum of causative mutations and mechanisms. Here, we provide a comprehensive review of the approaches currently in development including a discussion of retinal neuroprotection, gene therapies (gene augmentation, gene editing, RNA modification, optogenetics), and regenerative stem or precursor cell-based therapies. Our review focuses on technologies that are being developed for clinical translation or are in active clinical trials and discusses the advantages and limitations for each approach.

Stable oxime-crosslinked hyaluronan-based hydrogel as a biomimetic vitreous substitute.

Vitreous substitutes are clinically used to maintain retinal apposition and preserve retinal function; yet the most used substitutes are gases and oils which have disadvantages including strict face-down positioning post-surgery and the need for subsequent surgical removal, respectively. We have engineered a vitreous substitute comprised of a novel hyaluronan-oxime crosslinked hydrogel. Hyaluronan, which is naturally abundant in the vitreous of the eye, is chemically modified to crosslink with poly(ethylene glycol)-tetraoxyamine via oxime chemistry to produce a vitreous substitute that has similar physical properties to the native vitreous including refractive index, density and transparency. The oxime hydrogel is cytocompatible in vitro with photoreceptors from mouse retinal explants and biocompatible in rabbit eyes as determined by histology of the inner nuclear layer and photoreceptors in the outer nuclear layer. The ocular pressure in the rabbit eyes was consistent over 56 d, demonstrating limited to no swelling. Our vitreous substitute was stable in vivo over 28 d after which it began to degrade, with approximately 50% loss by day 56. We confirmed that the implanted hydrogel did not impact retina function using electroretinography over 90 days versus eyes injected with balanced saline solution. This new oxime hydrogel provides a significant improvement over the status quo as a vitreous substitute.