Frequency and Distribution of Ophthalmic Surgical Procedures among Patients with Inherited Retinal Diseases

OBJECTIVE

In this study, we aimed to characterize the frequency and distribution of ocular surgeries in patients with inherited retinal diseases (IRDs) and evaluate associated patient and disease factors.

DESIGN

Retrospective cohort.

PARTICIPANTS

Subjects aged ≥ 18 years who were followed at the Johns Hopkins Genetic Eye Disease Center.

METHODS

We studied a retrospective cohort of patients with an IRD diagnosis to analyze the occurrence of laser and incisional surgeries. Subjects were categorized into 2 groups: central dysfunction (macular/cone/cone-rod dystrophy, "MCCRD group") and panretinal or peripheral dysfunction (retinitis pigmentosa-like, "RP group"). Genetic testing status was recorded. The association of patient and disease factors on the frequency, distribution, and timing of surgeries was analyzed.

MAIN OUTCOME MEASURES

Prevalence, prevalence odds ratio (POR), hazard ratio (HR) of ophthalmic procedures by phenotype.

RESULTS

A total of 1472 eyes of 736 subjects were evaluated. Among them, 31.3% (n = 230) had undergone ocular surgery, and 78.3% of those (n = 180/230) had a history of more than 1 surgery. A total of 602 surgical procedures were analyzed. Cataract extraction with intraocular lens implantation (CEIOL) was the most common (51.2%), followed by yttrium aluminum garnet capsulotomy, refractive surgery, retinal surgery, and others. Cataract extraction with intraocular lens implantation occurred more frequently in RP than in MCCRD subjects (POR, 2.59; P = 0.002). Retinitis pigmentosa subjects underwent CEIOL at a younger age than patients with MCCRD (HR, 2.11; P < 0.001).

CONCLUSIONS

Approximately one-third of patients with IRD had a history of laser or incisional surgery. Cataract extraction with intraocular lens implantation was the most common surgery; its frequency and timing may be associated with the IRD phenotype. This data may inform the design of prospective research. Such efforts may illuminate routine clinical decision-making and contribute to surgical strategy development for cell and gene therapy delivery.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Automated identification of fleck lesions in Stargardt disease using deep learning enhances lesion detection sensitivity and enables morphometric analysis of flecks

PURPOSE

To classify fleck lesions and assess artificial intelligence (AI) in identifying flecks in Stargardt disease (STGD).

METHODS

A retrospective study of 170 eyes from 85 consecutive patients with confirmed STGD. Fundus autofluorescence images were extracted, and flecks were manually outlined. A deep learning model was trained, and a hold-out testing subset was used to compare with manually identified flecks and for graders to assess. Flecks were clustered using K-means clustering.

RESULTS

Of the 85 subjects, 45 were female, and the median age was 37 years (IQR 25-59). A subset of subjects (n=41) had clearly identifiable fleck lesions, and an AI was successfully trained to identify these lesions (average Dice score of 0.53, n=18). The AI segmentation had smaller (0.018 compared with 0.034 mm2, p<0.001) but more numerous flecks (75.5 per retina compared with 40.0, p<0.001), but the total size of flecks was not different. The AI model had higher sensitivity to detect flecks but resulted in more false positives. There were two clusters of flecks based on morphology: broadly, one cluster of small round flecks and another of large amorphous flecks. The per cent frequency of small round flecks negatively correlated with subject age (r=-0.31, p<0.005).

CONCLUSIONS

AI-based detection of flecks shows greater sensitivity than human graders but with a higher false-positive rate. With further optimisation to address current shortcomings, this approach could be used to prescreen subjects for clinical research. The feasibility and utility of quantifying fleck morphology in conjunction with AI-based segmentation as a biomarker of progression require further study.

Transpupillary-Guided Trans-Scleral Transplantation of Subretinal Grafts in a Retinal Degeneration Mouse Model

Transplantation of photoreceptor cells and retinal pigment epithelial (RPE) cells provide a potential therapy for retinal degeneration diseases. Subretinal transplantation of therapeutic donor cells into mouse recipients is challenging due to the limited surgical space allowed by the small volume of the mouse eye. We developed a trans-scleral surgical transplantation platform with direct transpupillary vision guidance to facilitate the subretinal delivery of exogenous cells in mouse recipients. The platform was tested using retinal cell suspensions and three-dimensional retinal sheets collected from rod-rich Rho::EGFP mice and cone-rich OPN1LW-EGFP;NRL-/- mice, respectively. Live/dead assay showed low cell mortality for both forms of donor cells. Retinal grafts were successfully delivered into the subretinal space of a mouse model of retinal degeneration, Rd1/NS, with minimum surgical complications as detected by multimodal confocal scanning laser ophthalmoscope (cSLO) imaging. Two months post-transplantation, histological staining demonstrated evidence of advanced maturation of the retinal grafts into 'adult' rods and cones (by robust Rho::EGFP, S-opsin, and OPN1LW:EGFP expression, respectively) in the subretinal space. Here, we provide a surgical platform that can enable highly accurate subretinal delivery with a low rate of complications in mouse recipients. This technique offers precision and relative ease of skill acquisition. Furthermore, the technique could be used not only for studies of subretinal cell transplantation but also for other intraocular therapeutic studies including gene therapies.

Multimodal Phenomap of Stargardt Disease Integrating Structural, Psychophysical, and Electrophysiologic Measures of Retinal Degeneration

Objective

To cluster the diverse phenotypic features of Stargardt disease (STGD) using unsupervised clustering of multimodal retinal structure and function data.

Design

Retrospective cross-sectional study.

Subjects

Eyes of subjects with STGD and fundus autofluorescence (FAF), OCT, electroretinography (ERG), and microperimetry (MP) data available within 1 year of the baseline evaluation.

Methods

A total of 46 variables from FAF, OCT, ERG, and MP results were recorded for subjects with STGD as defined per published criteria. Factor analysis of mixed data identified the most informative variables. Unsupervised hierarchical clustering and silhouette analysis identified the optimal number of clusters to classify multimodal phenotypes.

Main Outcome Measures

Phenotypic clusters of STGD subjects and the corresponding cluster features.

Results

We included 52 subjects and 102 eyes with a mean visual acuity (VA) at the time of multimodal testing of 0.69 ± 0.494 logarithm of minimum angle of resolution (20/63 Snellen). We identified 4 clusters of eyes. Compared to the other clusters, cluster 1 (n = 16) included younger subjects, VA greater than that of clusters 2 and 3, normal or moderately low total macular volume (TMV), greater preservation of scotopic and photopic ERG responses and fixation stability, less atrophy, and fewer flecks. Cluster 2 (n = 49) differed from cluster 1 mainly with less atrophy and relatively stable fixation. Cluster 3 (n = 10) included older subjects than clusters 1 and 2 and showed the lowest VA, TMV, ERG responses, and fixation stability, with extensive atrophy. Cluster 4 (n = 27) showed better VA, TMV similar to clusters 1 and 2, moderate ERG activity, stable fixation, and moderate-high atrophy and flecks.

Conclusions

Reflecting the phenotypic complexity of STGD, an unsupervised clustering approach incorporating phenotypic measures can be used to categorize STGD eyes into distinct clusters. The clusters exhibit differences in structural and functional measures including quantity of flecks, extent of retinal atrophy, visual fixation accuracy, and ERG responses, among other features. If novel pharmacologic, gene, or cell therapy modalities become available in the future, the multimodal phenomap approach may be useful to individualize treatment decisions, and its utility in aiding prognostication requires further evaluation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Comparative Analysis of Single-cell and Single-nucleus RNA-sequencing in a Rabbit Model of Retinal Detachment-related Proliferative Vitreoretinopathy

Purpose

Proliferative vitreoretinopathy (PVR) is the most common cause of failure of retinal reattachment surgery, and the molecular changes leading to this aberrant wound healing process are currently unknown. Our ultimate goal is to study PVR pathogenesis by employing single-cell transcriptomics to dissect cellular heterogeneity.

Design

Here we aimed to compare single-cell RNA sequencing (scRNA-seq)  and single-nucleus RNA-sequencing (snRNA-seq) of retinal PVR samples in the rabbit model.

Participants

Unilateral induction of PVR lesions in rabbit eyes with contralateral eyes serving as controls.

Methods

Proliferative vitreoretinopathy was induced unilaterally in Dutch Belted rabbits. At different timepoints after PVR induction, retinas were dissociated into either cells or nuclei suspension and processed for scRNA-seq or snRNA-seq.

Main Outcome Measures

Single cell and nuclei transcriptomic profiles of retinas after PVR induction.

Results

Single-cell RNA sequencing and snRNA-seq were conducted on retinas at 4 hours and 14 days after disease induction. Although the capture rate of unique molecular identifiers and genes were greater in scRNA-seq samples, overall gene expression profiles of individual cell types were highly correlated between scRNA-seq and snRNA-seq. A major disparity between the 2 sequencing modalities was the cell type capture rate, however, with glial cell types overrepresented in scRNA-seq, and inner retinal neurons were enriched by snRNA-seq. Furthermore, fibrotic Müller glia were overrepresented in snRNA-seq samples, whereas reactive Müller glia were overrepresented in scRNA-seq samples. Trajectory analyses were similar between the 2 methods, allowing for the combined analysis of the scRNA-seq and snRNA-seq data sets.

Conclusions

These findings highlight limitations of both scRNA-seq and snRNA-seq analysis and imply that use of both techniques together can more accurately identify transcriptional networks critical for aberrant fibrogenesis in PVR than using either in isolation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Transition to Chronic Fibrosis in an Animal Model of Retinal Detachment With Features of Proliferative Vitreoretinopathy

Purpose

Proliferative vitreoretinopathy (PVR) is the most common cause of failure of surgically repaired rhegmatogenous retinal detachment (RRD). Chemically induced and cell injection PVR models do not fully simulate the clinical characteristics of PVR in the post-RRD context. There is an unmet need for translational models in which to study mechanisms and treatments specific to RRD-PVR.

Methods

RRD was induced in adult Dutch Belted rabbits. Posterior segments were fixed or processed for RNA sequencing at 6 hours and 2, 7, 14, and 35 days after induction. Histochemical staining and immunolabeling for glial fibrillary acidic protein, alpha smooth muscle actin, vascular endothelial growth factor receptor 2, CD68, and RPE 65 kDa protein were performed, and labeling intensity was scored. Single cell RNA sequencing was performed.

Results

Acute histopathological changes included intravitreal and intraretinal hemorrhage, leukocytic vitritis, chorioretinitis, and retinal rarefaction. Chronic lesions showed retinal atrophy, gliosis, fibrotic subretinal membranes, and epiretinal fibrovascular proliferation. Fibrillar collagen was present in the fibrocellular and fibrovascular membranes in chronic lesions. Moderate to strong labeling of glia and vasculature was detected in chronic lesions. At day 14, most cells profiled by single cell sequencing were identified as Mϋller glia and microglia, consistent with immunolabeling. Expression of several fibrillar collagen genes was upregulated in chronic lesions.

Conclusions

Histological and transcriptional features of this rabbit model simulate important features of human RRD-PVR, including the transition to chronic intraretinal and periretinal fibrosis. This animal model of RRD with features of PVR will enable further research on targeted treatment interventions.

Prediction of visual impairment in retinitis pigmentosa using deep learning and multimodal fundus images

BACKGROUND

The efficiency of clinical trials for retinitis pigmentosa (RP) treatment is limited by the screening burden and lack of reliable surrogate markers for functional end points. Automated methods to determine visual acuity (VA) may help address these challenges. We aimed to determine if VA could be estimated using confocal scanning laser ophthalmoscopy (cSLO) imaging and deep learning (DL).

METHODS

Snellen corrected VA and cSLO imaging were obtained retrospectively. The Johns Hopkins University (JHU) dataset was used for 10-fold cross-validations and internal testing. The Amsterdam University Medical Centers (AUMC) dataset was used for external independent testing. Both datasets had the same exclusion criteria: visually significant media opacities and images not centred on the central macula. The JHU dataset included patients with RP with and without molecular confirmation. The AUMC dataset only included molecularly confirmed patients with RP. Using transfer learning, three versions of the ResNet-152 neural network were trained: infrared (IR), optical coherence tomography (OCT) and combined image (CI).

RESULTS

In internal testing (JHU dataset, 2569 images, 462 eyes, 231 patients), the area under the curve (AUC) for the binary classification task of distinguishing between Snellen VA 20/40 or better and worse than Snellen VA 20/40 was 0.83, 0.87 and 0.85 for IR, OCT and CI, respectively. In external testing (AUMC dataset, 349 images, 166 eyes, 83 patients), the AUC was 0.78, 0.87 and 0.85 for IR, OCT and CI, respectively.

CONCLUSIONS

Our algorithm showed robust performance in predicting visual impairment in patients with RP, thus providing proof-of-concept for predicting structure-function correlation based solely on cSLO imaging in patients with RP.

Very Large Cystoid Macular Lesions Identified Using Outlier Analysis of Genetically Confirmed Inherited Retinal Disease Cases

BACKGROUND

Cystoid macular lesions (CML) in inherited retinal diseases (IRDs) can contribute to vision impairment. Studying the morphologic range and outlier presentations of CML may inform clinical associations, mechanistic research, and trial design. Thus, we aim to describe the distribution of optical coherence tomography (OCT) parameters in IRD cases with CML and identify phenotype-genotype associations in very large cystoid macular lesions (VLCML).

MATERIALS AND METHODS

This cross-sectional study retrieved clinical information from electronic records from January 2020 to December 2021. VLCML cases were identified using the robust distance (Mahalanobis) of the correlation between central foveal thickness (CFT) and total macular volume (TMV) and a 99.9% probability ellipse. The distribution of OCT parameters was calculated by genotype and phenotype.

RESULTS

We included 173 eyes of 103 subjects. The median age was 55.9 (interquartile range [IQR], 37.9, 63.7) and 47.6% (49/103) were females. Patients had disease-causing mutations in 30 genes. The most common genes included USH2A (n = 18), RP1 (n = 12), and ABCA4 (n = 11). Robust distance analysis showed that the prevalence of VLCML was 1.94% (n = 2 patients, 4 eyes). VLCML was seen in cases of NR2E3 (119-2A>C) and BEST1 (1120_1121insG) mutations. The median CFT in cases without VLCML was 269 µm (IQR 209, 318.50) while the median for VLCML cases was 1,490 µm (IQR 1,445.50, 1,548.00) (P < .001).

CONCLUSIONS

Subjects with different IRD genotypes may develop VLCMLs. Future studies could consider the range and outlier values of CML foveal thickness when determining inclusion criteria and biostatistical plans for observational and interventional studies.

Single-cell transcriptome analysis of xenotransplanted human retinal organoids defines two migratory cell populations of nonretinal origin

Human retinal organoid transplantation could potentially be a treatment for degenerative retinal diseases. How the recipient retina regulates the survival, maturation, and proliferation of transplanted organoid cells is unknown. We transplanted human retinal organoid-derived cells into photoreceptor-deficient mice and conducted histology and single-cell RNA sequencing alongside time-matched cultured retinal organoids. Unexpectedly, we observed human cells that migrated into all recipient retinal layers and traveled long distances. Using an unbiased approach, we identified these cells as astrocytes and brain/spinal cord-like neural precursors that were absent or rare in stage-matched cultured organoids. In contrast, retinal progenitor-derived rods and cones remained in the subretinal space, maturing more rapidly than those in the cultured controls. These data suggest that recipient microenvironment promotes the maturation of transplanted photoreceptors while inducing or facilitating the survival of migratory cell populations that are not normally derived from retinal progenitors. These findings have important implications for potential cell-based treatments of retinal diseases.

Bioengineering strategies for restoring vision

Late-stage retinal degenerative disease involving photoreceptor loss can be treated by optogenetic therapy, cell transplantation and retinal prostheses. These approaches aim to restore light sensitivity to the retina as well as visual perception by integrating neuronal responses for transmission to the cortex. In age-related macular degeneration, some cell-based therapies also aim to restore photoreceptor-supporting tissue to prevent complete photoreceptor loss. In the earlier stages of degeneration, gene-replacement therapy could attenuate retinal-disease progression and reverse loss of function. And gene-editing strategies aim to correct the underlying genetic defects. In this Review, we highlight the most promising gene therapies, cell therapies and retinal prostheses for the treatment of retinal disease, discuss the benefits and drawbacks of each treatment strategy and the factors influencing whether functional tissue is reconstructed and repaired or replaced with an electronic device, and summarize upcoming technologies for enhancing the restoration of vision.

Risk of Tertiary, Quaternary, and Quinary Proliferative Vitreoretinopathy: Analysis of a Nationwide Database (2010-2017)

OBJECTIVE

Primary proliferative vitreoretinopathy (PVR) is established as an important cause of the failed repair of a fresh retinal detachment (RD) and the consequent need for secondary repair. However, the burden of multiple repairs beyond the initial failure has not been studied in detail. We aimed to determine the association between primary PVR and the occurrence of tertiary, quaternary, and quinary RD repairs, using a nationwide database.

DESIGN

Retrospective cohort study of insurance claims.

SUBJECTS

Cases of rhegmatogenous RD that underwent primary surgical repair.

METHODS

Cases of primary RD repair from 2010 to 2017 were categorized based on the absence (P0 group) or presence (P1 group) of primary PVR. In each group, we analyzed the frequency of subsequent RD repair procedures with concurrent PVR.

MAIN OUTCOME MEASURE

The risk of secondary and higher multiples of PVR-associated RD repair.

RESULTS

A total of 27 137 cases were included, with 24 500 (90.3%) in the P0 group and 2637 (9.7%) in the P1 group. The frequency (%) of cases ultimately requiring secondary, tertiary, quaternary, and quinary repair in P0 versus P1 was 1.88 versus 10.24 (P < 0.001), 0.26 versus 2.50 (P < 0.001), 0.07 versus 0.64 (P < 0.001), and 0.03 versus 0.08 (P = 0.272), respectively. The risk of undergoing secondary repair was higher in the P1 than in the P0 group (hazard ratio [HR], 6.02; 95% confidence interval [CI], 5.24-6.92; P < 0.001). The risk of undergoing tertiary repair was also higher in the P1 than in the P0 group (HR, 1.67; CI, 1.23-2.28; P = 0.001). There was no difference in the risk of undergoing quaternary repair between the groups (HR, 0.76; CI, 0.41-1.40; P = 0.37). Senary repairs were not detected in this dataset.

CONCLUSIONS

Primary PVR may increase the risk of requiring multiple sequential retinal reattachment surgeries beyond the initial repair failure. Retinal detachment cases with primary PVR at the initial presentation of RD were more likely to undergo secondary and tertiary repairs than cases without primary PVR. Health care claims analysis may be a useful tool to study population-based estimates for multiple recurrences of RD in cases with PVR.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Cell-specific regulation of gene expression using splicing-dependent frameshifting

Precise and reliable cell-specific gene delivery remains technically challenging. Here we report a splicing-based approach for controlling gene expression whereby separate translational reading frames are coupled to the inclusion or exclusion of mutated, frameshifting cell-specific alternative exons. Candidate exons are identified by analyzing thousands of publicly available RNA sequencing datasets and filtering by cell specificity, conservation, and local intron length. This method, which we denote splicing-linked expression design (SLED), can be combined in a Boolean manner with existing techniques such as minipromoters and viral capsids. SLED can use strong constitutive promoters, without sacrificing precision, by decoupling the tradeoff between promoter strength and selectivity. AAV-packaged SLED vectors can selectively deliver fluorescent reporters and calcium indicators to various neuronal subtypes in vivo. We also demonstrate gene therapy utility by creating SLED vectors that can target PRPH2 and SF3B1 mutations. The flexibility of SLED technology enables creative avenues for basic and translational research.

Risk of Cystoid Macular Edema after Cataract Surgery in Retinitis Pigmentosa: An Analysis of United States Claims from 2010 to 2018

PURPOSE

Cataract surgery is commonly performed to improve vision in patients with retinitis pigmentosa (RP). However, the risk of postoperative cystoid macular edema (CME) in RP remains unclear. Here, we leveraged a large multiyear claims database to estimate the risk of CME after cataract surgery in patients with and without RP.

DESIGN

Retrospective multicenter cohort.

SUBJECTS

Patients aged 18 to 65 years who underwent single-phase cataract surgery between January 1, 2020, and December 31, 2018. Identified using the IBM MarketScan claims database.

METHODS

We evaluated the baseline characteristics and outcomes and estimated the hazard ratio (HR) using a multivariable mixed-effects approach. The eyes of patients with RP were categorized as group R1, and those without diagnoses of RP by the time of surgery were categorized as group R0.

MAIN OUTCOME MEASURES

Incident postoperative CME in the same eye that underwent cataract extraction within 12 months of the procedure.

RESULTS

We included 468 123 patients and 615 645 eyes. This included 124 eyes with RP (R1) and 615 521 without RP (R0). The mean ages were 50.5 ± 9.8 years in R1 and 57.9 ± 6.1 years in R0. The cumulative incidence of CME at 12 months was 5.8% (95% confidence interval [CI] 1.2%-10.3%) in R1, and it was 1.1% (95% CI 1.1%-1.2%) in R0. On average, CME was reported in R1 subjects 3.9 weeks later than in R0 subjects (95% CI 2.04-6.5 weeks; P <0.001). The subjects in R1 had 4.83 (95% CI 2.13-10.93, P <0.001) times the risk of CME compared to the subjects in R0. A stratified analysis showed that epiretinal membrane (ERM) decreased the risk of CME in R1 (HR 0.12 [95% CI 0.48-0.97; P = 0.004]) but increased it in R0 (HR, 4.32 [95% CI 3.13-5.95; P <0.001]).

CONCLUSIONS

The cataract surgery-related risk of CME among patients with RP may be >4 times that among people without RP. Men and individuals aged 18 to 34 and 55 to 65 years may be at the greatest risk, whereas ERM may lower the risk. Further study is warranted to stratify the risk by RP genotype and phenotype and illuminate the natural history, angiographic features, and functional consequences of postoperative CME.

Tissue-specific genotype-phenotype correlations among USH2A-related disorders in the RUSH2A study

We assessed genotype-phenotype correlations among the visual, auditory, and olfactory phenotypes of 127 participants with Usher syndrome (USH2) (n=80) or nonsyndromic autosomal recessive retinitis pigmentosa (ARRP) (n=47) due to USH2A variants, using clinical data and molecular diagnostics from the Rate of Progression in USH2A Related Retinal Degeneration (RUSH2A) study. USH2A truncating alleles were associated with USH2 and had a dose-dependent effect on hearing loss severity with no effect on visual loss severity within the USH2 subgroup. A group of missense alleles in an inter-fibronectin domain appeared to be hypomorphic in ARRP. These alleles were associated with later age of onset, larger visual field area, better sensitivity thresholds, and better electroretinographic responses. No effect of genotype on the severity of olfactory deficits was observed. This study unveils a unique, tissue-specific USH2A allelic hierarchy with important prognostic implications for patient counseling and treatment trial endpoints. These findings may inform clinical care or research approaches in others with allelic disorders or pleiotropic phenotypes. This article is protected by copyright. All rights reserved.

Spatial Characteristics of Peripheral Visual Islands in Retinitis Pigmentosa

Purpose

Retinitis pigmentosa (RP) is typified by progressive peripheral visual field (pVF) loss in patterns that can vary between individuals. Greater understanding of pVF preservation may inform research on therapeutic targets. However, characteristics of retained pVF are incompletely understood. We aimed to evaluate the spatial characteristics of retained pVF in RP.

Methods

We developed a computational platform to generate a probability map of the spatial distribution of retained pVF loci using the Goldmann V4e isopter. RP subjects were grouped into cross-sectional and longitudinal datasets. Probability maps of retained pVF were generated for categories of symptomatic disease duration (SDD). We applied a mathematical model to determine the anatomical correlate of the retained pVF.

Results

A total of 152 subjects were included. The mean age was 46.7 years. SDD was <20 years (47.4%), 20 to 40 years (39.5%), or >40 years (13.2%). Longitudinal data (3.2–5.7 years of follow up) were available for 65 subjects. In the cross-sectional dataset, retained pVF loci were most likely to be located between the 50° and 80° isoeccentric meridians and between the 30° to 50° radial axes. In the longitudinal dataset, inferotemporal pVF loci were the most likely to be preserved over time. The area of pVF retention corresponded anatomically to the pre-equatorial superonasal retina.

Conclusions

Semiautomated quantitation of pVF may be a useful tool to analyze spatial characteristics of VF in RP. Retinal cells in the superonasal periphery may be resilient to RP-related functional decline. Understanding the cellular and molecular basis of pVF resilience in the retina may inform efforts to develop treatment modalities for RP.

The Direct Healthcare Cost of Stargardt Disease: A Claims-Based Analysis

Purpose: Stargardt disease (SD) is the most common juvenile macular degeneration and a leading cause of uncorrectable childhood blindness. The progressive and incurable nature of this chronic condition entails a long-term financial burden on affected individuals. The economic costs of SD have not been characterized in detail, so we aimed to estimate the direct healthcare cost of SD.Methods: Outpatient administrative claims data (2010-2014) for patients with SD were analyzed from the IBM® MarketScan® Commercial Claims and Encounters Database. Two comparison groups were selected: nonexudative age-related macular degeneration (AMD) and bilateral sensorineural hearing loss (SHL). Gross median payments per year of insurance coverage were calculated.Results: A total of 472,428 patients were analyzed (5,015 SD, 369,750 SHL and 97,663 AMD patients respectively). The payment per year of insurance coverage for SD (median: 105.58 USD, IQR: 50.53 USD-218.71 USD) was higher than that of SHL (median: 51.01 USD, IQR: 25.66 USD-121.66 USD, p < .001) and AMD (median: 76.20 USD, IQR: 38.00 USD-164.86 USD, p < .001). When adjusted for age, sex, year of first service, and type of benefit plan, the annual payment for SD was 47.83 USD higher than SHL (p < .001) and 17.34 USD higher than AMD (p < .001).Conclusions: There is a significant direct healthcare cost associated with SD. The annual per-patient cost of SD was higher than SHL, another condition that causes sensory impairment in people of all ages, and nonexudative AMD which causes a similar pattern of visual loss that typically begins later in life. The total lifetime per-patient cost of SD may exceed that of nonexudative AMD.

Localized Structural and Functional Deficits in a Nonhuman Primate Model of Outer Retinal Atrophy

Purpose

Cell-based therapy development for geographic atrophy (GA) in age-related macular degeneration (AMD) is hampered by the paucity of models of localized photoreceptor and retinal pigment epithelium (RPE) degeneration. We aimed to characterize the structural and functional deficits in a laser-induced nonhuman primate model, including an analysis of the choroid.

Methods

Macular laser photocoagulation was applied in four macaques. Fundus photography, optical coherence tomography (OCT), dye angiography, and OCT-angiography were conducted over 4.5 months, with histological correlation. Longitudinal changes in spatially resolved macular dysfunction were measured using multifocal electroretinography (MFERG).

Results

Lesion features, depending on laser settings, included photoreceptor layer degeneration, inner retinal sparing, skip lesions, RPE elevation, and neovascularization. The intralesional choroid was degenerated. The normalized mean MFERG amplitude within lesions was consistently lower than control regions (0.94 ± 0.35 vs. 1.10 ± 0.27, P = 0.032 at month 1, 0.67 ± 0.22 vs. 0.83 ± 0.15, P = 0.0002 at month 2, and 0.97 ± 0.31 vs. 1.20 ± 0.21, P < 0.0001 at month 3.5). The intertest variation of mean MFERG amplitudes in rings 1 to 5 ranged from 13.0% to 26.0% in normal eyes.

Conclusions

Laser application in this model caused localized outer retinal, RPE, and choriocapillaris loss. Localized dysfunction was apparent by MFERG in the first month after lesion induction. Correlative structure-function testing may be useful for research on the functional effects of stem cell-based therapy for GA. MFERG amplitude data should be interpreted in the context of relatively high intertest variability of the rings that correspond to the central macula. Sustained choroidal insufficiency may limit long-term subretinal graft viability in this model.

Pluripotent stem cell therapy for retinal diseases

Pluripotent stem cells (PSCs), which include human embryonic stem cells (hESCs) and induced pluripotent stem cell (iPSC), have been used to study development of disease processes, and as potential therapies in multiple organ systems. In recent years, there has been increasing interest in the use of PSC-based transplantation to treat disorders of the retina in which retinal cells have been functionally damaged or lost through degeneration. The retina, which consists of neuronal tissue, provides an excellent system to test the therapeutic utility of PSC-based transplantation due to its accessibility and the availability of high-resolution imaging technology to evaluate effects. Preclinical trials in animal models of retinal diseases have shown improvement in visual outcomes following subretinal transplantation of PSC-derived photoreceptors or retinal pigment epithelium (RPE) cells. This review focuses on preclinical studies and clinical trials exploring the use of PSCs for retinal diseases. To date, several phase I/II clinical trials in patients with age-related macular degeneration (AMD) and Stargardt disease (STGD1) have demonstrated the safety and feasibility of PSC-derived RPE transplantation. Additional phase I/II clinical trials using PSC-derived RPE or photoreceptor cells for the treatment of AMD, STGD1, and also retinitis pigmentosa (RP) are currently in the pipeline. As this field continues to evolve, additional technologies may enhance PSC-derived cell transplantation through gene-editing of autologous cells, transplantation of more complex cellular structures such as organoids, and monitoring of transplanted cells through novel imaging technologies.

Characterization and allogeneic transplantation of a novel transgenic cone-rich donor mouse line

OBJECTIVES

Cone photoreceptor transplantation is a potential treatment for macular diseases. The optimal conditions for cone transplantation are poorly understood, partly because of the scarcity of cones in donor mice. To facilitate allogeneic cone photoreceptor transplantation studies in mice, we aimed to create and characterize a donor mouse model containing a cone-rich retina with a cone-specific enhanced green fluorescent protein (EGFP) reporter.

METHODS

We generated OPN1LW-EGFP/NRL^-/- mice by crossing NRL^-/- and OPN1LW-EGFP mice. We characterized the anatomical phenotype of OPN1LW-EGFP/NRL^-/- mice using multimodal confocal scanning laser ophthalmoscopy (cSLO) imaging, immunohistology, and transmission electron microscopy. We evaluated retinal function using electroretinography (ERG), including 465 and 525 nm chromatic stimuli. Retinal sheets and cell suspensions from OPN1LW-EGFP/NRL^-/- mice were transplanted subretinally into immunodeficient Rd1 mice.

RESULTS

OPN1LW-EGFP/NRL^-/- retinas were enriched with OPN1LW-EGFP⁺ and S-opsin⁺ cone photoreceptors in a dorsal-ventral distribution gradient. Cone photoreceptors co-expressing OPNL1W-EGFP and S-opsin significantly increased in OPN1LW-EGFP/NRL^-/- compared to OPN1LW-EGFP mice. Temporal dynamics of rosette formation in the OPN1LW-EGFP/NRL^-/- were similar as the NRL^-/- with peak formation at P15. Rosettes formed preferentially in the ventral retina. The outer retina in P35 OPN1LW-EGFP/NRL^-/- was thinner than NRL^-/- controls. The OPN1LW-EGFP/NRL^-/- ERG response amplitudes to 465 nm stimulation were similar to, but to 535 nm stimulation were lower than, NRL^-/- controls. Three months after transplantation, the suspension grafts showed greater macroscopic degradation than sheet grafts. Retinal sheet grafts from OPN1LW-EGFP/NRL^-/- mice showed greater S-opsin ⁺ cone survival than suspension grafts from the same strain.

CONCLUSIONS

OPN1LW-EGFP/NRL^-/- retinae were enriched with S-opsin⁺ photoreceptors. Sustained expression of EGFP facilitated the longitudinal tracking of transplanted donor cells. Transplantation of cone-rich retinal grafts harvested prior to peak rosette formation survived and differentiated into cone photoreceptor subtypes. Photoreceptor sheet transplantation may promote greater macroscopic graft integrity and S-opsin⁺ cone survival than cell suspension transplantation, although the mechanism underlying this observation is unclear at present. This novel cone-rich reporter mouse strain may be useful to study the influence of graft structure on cone survival.

Optical coherence tomography angiography of astrocytic hamartoma demonstrates intrinsic vascularity

Purpose

To evaluate the findings of astrocytic hamartoma in the setting of gyrate atrophy, including details of optical coherence tomography angiography (OCTA).

Observations

Multimodal imaging was obtained on a 20-year-old woman with genetically-confirmed gyrate atrophy. Dilated fundus exam was performed, followed by ultra-widefield color and green autofluorescence imaging and OCTA of bilateral peripapillary and optic disc lesions. Clinical and imaging findings were consistent with gyrate atrophy. The bilateral peripapillary and optic disc lesions had a glistening, translucent, and mulberry-like appearance. OCTA imaging of these lesions clearly demonstrated an intrinsic vascular network and hyporeflective spaces within the lesion, which could not be seen on routine examination.

Conclusions and importance

OCTA was used to noninvasively diagnose astrocytic hamartoma in this patient with gyrate atrophy by showing the intrinsic vasculature and hyporeflective spaces of the lesion. This imaging modality can help differentiate astrocytic hamartoma from other lesions that typically lack intrinsic vascularity, such as optic disc drusen.

Oral N-acetylcysteine improves cone function in retinitis pigmentosa patients in phase I trial

BACKGROUNDIn retinitis pigmentosa (RP), rod photoreceptors degenerate from 1 of many mutations, after which cones are compromised by oxidative stress. N-acetylcysteine (NAC) reduces oxidative damage and increases cone function/survival in RP models. We tested the safety, tolerability, and visual function effects of oral NAC in RP patients.METHODSSubjects (n = 10 per cohort) received 600 mg (cohort 1), 1200 mg (cohort 2), or 1800 mg (cohort 3) NAC bid for 12 weeks and then tid for 12 weeks. Best-corrected visual acuity (BCVA), macular sensitivity, ellipsoid zone (EZ) width, and aqueous NAC were measured. Linear mixed-effects models were used to estimate the rates of changes during the treatment period.RESULTSThere were 9 drug-related gastrointestinal adverse events that resolved spontaneously or with dose reduction (maximum tolerated dose 1800 mg bid). During the 24-week treatment period, mean BCVA significantly improved at 0.4 (95% CI: 0.2-0.6, P < 0.001), 0.5 (95% CI: 0.3-0.7, P < 0.001), and 0.2 (95% CI: 0.02-0.4, P = 0.03) letters/month in cohorts 1, 2, and 3, respectively. There was no significant improvement in mean sensitivity over time in cohorts 1 and 2, but there was in cohort 3 (0.15 dB/month, 95% CI: 0.04-0.26). There was no significant change in mean EZ width in any cohort.CONCLUSIONOral NAC is safe and well tolerated in patients with moderately advanced RP and may improve suboptimally functioning macular cones. A randomized, placebo-controlled trial is needed to determine if oral NAC can provide long-term stabilization and/or improvement in visual function in patients with RP.TRIAL REGISTRATIONNCT03063021.FUNDINGMr. and Mrs. Robert Wallace, Mr. and Mrs. Jonathan Wallace, Rami and Eitan Armon, Marc Sumerlin, Cassandra Hanley, and Nacuity Pharmaceuticals, Inc.

Quantifiable In Vivo Imaging Biomarkers of Retinal Regeneration by Photoreceptor Cell Transplantation

Purpose

Short-term improvements in retinal anatomy are known to occur in preclinical models of photoreceptor transplantation. However, correlative changes over the long term are poorly understood. We aimed to develop a quantifiable imaging biomarker grading scheme, using noninvasive multimodal confocal scanning laser ophthalmoscopy (cSLO) imaging, to enable serial evaluation of photoreceptor transplantation over the long term.

Methods

Photoreceptor cell suspensions or sheets from rhodopsin-green fluorescent protein mice were transplanted subretinally, into either NOD.CB17-Prkdc^scid/J or C3H/HeJ-Pde6b^rd1 mice. Multimodal cSLO imaging was performed serially for up to three months after transplantation. Imaging biomarkers were scored, and a grade was defined for each eye by integrating the scores. Image grades were correlated with immunohistochemistry (IHC) data.

Results

Multimodal imaging enabled the extraction of quantitative imaging biomarkers including graft size, GFP intensity, graft length, on-target graft placement, intra-graft lamination, hemorrhage, retinal atrophy, and periretinal proliferation. Migration of transplanted material was observed. Changes in biomarker scores and grades were detected in 14/16 and 7/16 eyes, respectively. A high correlation was found between image grades and IHC parameters.

Conclusions

Serial evaluation of multiple imaging biomarkers, when integrated into a per-eye grading scheme, enabled comprehensive tracking of longitudinal changes in photoreceptor cell grafts over time. The application of systematic multimodal in vivo imaging could be useful in increasing the efficiency of preclinical retinal cell transplantation studies in rodents and other animal models.

Translational Relevance

By allowing longitudinal evaluation of the same animal over time, and providing quantifiable biomarkers, non-invasive multimodal imaging improves the efficiency of retinal transplantation studies in animal models. Such assays will facilitate the development of cell therapy for retinal diseases.

Retinal stem cell transplantation: Balancing safety and potential

Stem cell transplantation holds great promise as a potential treatment for currently incurable retinal degenerative diseases that cause poor vision and blindness. Recently, safety data have emerged from several Phase I/II clinical trials of retinal stem cell transplantation. These clinical trials, usually run in partnership with academic institutions, are based on sound preclinical studies and are focused on patient safety. However, reports of serious adverse events arising from cell therapy in other poorly regulated centers have now emerged in the lay and scientific press. While progress in stem cell research for blindness has been greeted with great enthusiasm by patients, scientists, doctors and industry alike, these adverse events have raised concerns about the safety of retinal stem cell transplantation and whether patients are truly protected from undue harm. The aim of this review is to summarize and appraise the safety of human retinal stem cell transplantation in the context of its potential to be developed into an effective treatment for retinal degenerative diseases.

Optical Coherence Tomography Angiography Imaging in Inherited Retinal Diseases

Optical coherence tomography angiography (OCTA) is a novel, noninvasive imaging modality that allows depth-resolved imaging of the microvasculature in the retina and the choroid. It is a powerful research tool to study the pathobiology of retinal diseases, including inherited retinal dystrophies. In this review, we provide an overview of the evolution of OCTA technology, compare the specifications of various OCTA devices, and summarize key findings from published OCTA studies in inherited retinal dystrophies including retinitis pigmentosa, Stargardt disease, Best vitelliform macular dystrophy, and choroideremia. OCTA imaging has provided new data on characteristics of these conditions and has contributed to a deeper understanding of inherited retinal disease.

An AAV Dual Vector Strategy Ameliorates the Stargardt Phenotype in Adult Abca4-/- Mice

The recent approval in the United States of the first adeno-associated viral (AAV) vector for the treatment of an inherited retinal degeneration validates this approach for the treatment of many other diseases. A major limiting factor continues to be the size restriction of the AAV transgene at under 5 kb. Stargardt disease is the most prevalent form of recessively inherited blindness and is caused by mutations in ABCA4, the gene that codes for ATP-binding cassette transporter protein family member 4, which has a coding sequence length of 6.8 kb. Dual vector approaches increase the capacity of AAV gene therapy, but at the cost of substantially reduced levels of target protein, which may be insufficient to achieve a therapeutic effect. Here we show that the efficacy of recombination of dual vectors is dependent on the length of DNA overlap between two transgenes. With optimized recombination, full-length ABCA4 protein is expressed in the photoreceptor outer segments of Abca4^-/- mice at levels sufficient to reduce bisretinoid formation and correct the autofluorescent phenotype. These observations support a dual vector approach in future clinical trials using AAV gene therapy to treat Stargardt disease.

Inner retinal vasculopathy in Zika virus disease

Purpose

Zika virus infection is associated with vision-threatening ocular complications including uveitis and outer retinopathy. The aim of this report is to describe a case of an adult patient with serologically confirmed Zika infection who presented with retinal vascular abnormalities that coincided with systemic post-viral neurological manifestations of the disease.

Observations

A 34-year-old white female presented with symptoms of peripheral neuropathy following serologically confirmed Zika virus infection that was acquired in Puerto Rico four months prior to presentation. Ocular evaluation revealed perifoveal microaneurysms which were not associated with visual symptoms.

Conclusions and importance

These data potentially expand the phenotypic spectrum of Zika virus retinopathy. In addition to outer retinal abnormalities which are well-described in infants and adults, inner retinal vascular abnormalities may also occur and may be temporally associated with post-viral neurological sequelae of Zika virus infection. Clinicians should be aware of potential retinal involvement in affected patients who present with neurological symptoms after recovery from acute Zika virus infection.

Emerging therapies for inherited retinal degeneration

Inherited retinal degenerative diseases, a genetically and phenotypically heterogeneous group of disorders, affect the function of photoreceptor cells and are among the leading causes of blindness. Recent advances in molecular genetics and cell biology are elucidating the pathophysiological mechanisms underlying these disorders and are helping to identify new therapeutic approaches, such as gene therapy, stem cell therapy, and optogenetics. Several of these approaches have entered the clinical phase of development. Artificial replacement of dying photoreceptor cells using retinal prostheses has received regulatory approval. Precise retinal imaging and testing of visual function are facilitating more efficient clinical trial design. In individual patients, disease stage will determine whether the therapeutic strategy should comprise photoreceptor cell rescue to delay or arrest vision loss or retinal replacement for vision restoration.

Tropism of engineered and evolved recombinant AAV serotypes in the rd1 mouse and ex vivo primate retina

There is much debate on the adeno-associated virus (AAV) serotype that best targets specific retinal cell types and the route of surgical delivery-intravitreal or subretinal. This study compared three of the most efficacious AAV vectors known to date in a mouse model of retinal degeneration (rd1 mouse) and macaque and human retinal explants. Green fluorescent protein (GFP) driven by a ubiquitous promoter was packaged into three AAV capsids: AAV2/8(Y733F), AAV2/2(quad Y-F) and AAV2/2(7m8). Overall, AAV2/2(7m8) transduced the largest area of retina and resulted in the highest level of GFP expression, followed by AAV2/2(quad Y-F) and AAV2/8(Y733F). AAV2/2(7m8) and AAV2/2(quad Y-F) both resulted in similar patterns of transduction whether they were injected intravitreally or subretinally. AAV2/8(Y733F) transduced a significantly smaller area of retina when injected intravitreally compared with subretinally. Retinal ganglion cells, horizontal cells and retinal pigment epithelium expressed relatively high levels of GFP in the mouse retina, whereas amacrine cells expressed low levels of GFP and bipolar cells were infrequently transduced. Cone cells were the most frequently transduced cell type in macaque retina explants, whereas Müller cells were the predominant transduced cell type in human retinal explants. Of the AAV serotypes tested, AAV2/2(7m8) was the most effective at transducing a range of cell types in degenerate mouse retina and macaque and human retinal explants.

Long-term restoration of visual function in end-stage retinal degeneration using subretinal human melanopsin gene therapy

Optogenetic strategies to restore vision in patients who are blind from end-stage retinal degenerations aim to render remaining retinal cells light sensitive once photoreceptors are lost. Here, we assessed long-term functional outcomes following subretinal delivery of the human melanopsin gene (OPN4) in the rd1 mouse model of retinal degeneration using an adeno-associated viral vector. Ectopic expression of OPN4 using a ubiquitous promoter resulted in cellular depolarization and ganglion cell action potential firing. Restoration of the pupil light reflex, behavioral light avoidance, and the ability to perform a task requiring basic image recognition were restored up to 13 mo following injection. These data suggest that melanopsin gene therapy via a subretinal route may be a viable and stable therapeutic option for the treatment of end-stage retinal degeneration in humans.

Evaluation of an Optimized Injection System for Retinal Gene Therapy in Human Patients

Many retinal gene therapy clinical trials require subretinal injections of small volumes of adeno-associated viral (AAV) vector solutions in patients with retinal dystrophies, using equipment not specifically designed for this purpose. We therefore evaluated an optimized injection system in order to identify variables that might influence the rate of injection and final dose of vector delivered. An optimized injection system was assembled with a 41G polytetrafluoroethylene tip for retinal gene therapy. Flow rate was recorded at relevant infusion pressures (2-22 psi [14-152 kPa]), different target pressures (0.02-30 mm Hg [0.003-4 kPa]) and temperatures (18°C vs. 36°C) using a semiautomated Accurus(®) Surgical System. Retention of AAV2/8 and AAV2/8(Y733F) vector was quantified after simulating loading/injection with or without 0.001% Pluronic(®) F-68 (PF-68). The optimized injection system provided a linear flow rate (μl/s)-to-infusion pressure (psi) relationship (y = 0.62x; r(2) = 0.99), independent of temperature and pressure changes relevant for intraocular surgery (18-36°C, 0.02-30 mm Hg). Differences in length of 41G polytetrafluoroethylene tips caused significant variation in flow rate (p < 0.001). Use of PF-68 significantly (p < 0.001) reduced loss of vector genomes in the injection system by 55% (AAV2/8) and 52% (AAV2/8(Y733F)). A customized subretinal injection system assembled using equipment currently available in the operating room can deliver a controlled volume of vector at a fixed rate across a range of possible clinical parameters encountered in vitreoretinal surgery. The inclusion of 0.001% PF-68 had a significant effect on the final dose of vector genomes delivered. The described technique is currently used successfully in a clinical trial.

Transplanted photoreceptor precursors transfer proteins to host photoreceptors by a mechanism of cytoplasmic fusion

Photoreceptor transplantation is a potential future treatment for blindness caused by retinal degeneration. Photoreceptor transplantation restores visual responses in end-stage retinal degeneration, but has also been assessed in non-degenerate retinas. In the latter scenario, subretinal transplantation places donor cells beneath an intact host outer nuclear layer (ONL) containing host photoreceptors. Here we show that host cells are labelled with the donor marker through cytoplasmic transfer—94±4.1% of apparently well-integrated donor cells containing both donor and host markers. We detect the occurrence of Cre-Lox recombination between donor and host photoreceptors, and we confirm the findings through FISH analysis of X and Y chromosomes in sex-discordant transplants. We do not find evidence of nuclear fusion of donor and host cells. The artefactual appearance of integrated donor cells in host retinas following transplantation is most commonly due to material transfer from donor cells. Understanding this novel mechanism may provide alternate therapeutic strategies at earlier stages of retinal degeneration.

Previous studies have used fluorescently labelled cells to demonstrate the incorporation of transplanted photoreceptor precursors into the mouse retina. Here, the authors show that fluorescent proteins are passed between the host and transplanted cells rather than migration of donor cells into the retina.

Single residue AAV capsid mutation improves transduction of photoreceptors in the Abca4-/- mouse and bipolar cells in the rd1 mouse and human retina ex vivo

Gene therapy using adeno-associated viral vectors (AAV) for the treatment of retinal degenerations has shown safety and efficacy in clinical trials. However, very high levels of vector expression may be necessary for the treatment of conditions such as Stargardt disease where a dual vector approach is potentially needed, or in optogenetic strategies for end-stage degeneration in order to achieve maximal light sensitivity. In this study, we assessed two vectors with single capsid mutations, rAAV2/2(Y444F) and rAAV2/8(Y733F) in their ability to transduce retina in the Abca4^-/- and rd1 mouse models of retinal degeneration. We noted significantly increased photoreceptor transduction using rAAV2/8(Y733F) in the Abca4^-/- mouse, in contrast to previous work where vectors tested in this model have shown low levels of photoreceptor transduction. Bipolar cell transduction was achieved following subretinal delivery of both vectors in the rd1 mouse, and via intravitreal delivery of rAAV2/2(Y444F). The successful use of rAAV2/8(Y733F) to target bipolar cells was further validated on human tissue using an ex-vivo culture system of retinal explants. Capsid mutant AAV vectors transduce human retinal cells and may be particularly suited to treating retinal degenerations in which high levels of transgene expression are required.

Function of human pluripotent stem cell-derived photoreceptor progenitors in blind mice

Photoreceptor degeneration due to retinitis pigmentosa (RP) is a primary cause of inherited retinal blindness. Photoreceptor cell-replacement may hold the potential for repair in a completely degenerate retina by reinstating light sensitive cells to form connections that relay information to downstream retinal layers. This study assessed the therapeutic potential of photoreceptor progenitors derived from human embryonic and induced pluripotent stem cells (ESCs and iPSCs) using a protocol that is suitable for future clinical trials. ESCs and iPSCs were cultured in four specific stages under defined conditions, resulting in generation of a near-homogeneous population of photoreceptor-like progenitors. Following transplantation into mice with end-stage retinal degeneration, these cells differentiated into photoreceptors and formed a cell layer connected with host retinal neurons. Visual function was partially restored in treated animals, as evidenced by two visual behavioral tests. Furthermore, the magnitude of functional improvement was positively correlated with the number of engrafted cells. Similar efficacy was observed using either ESCs or iPSCs as source material. These data validate the potential of human pluripotent stem cells for photoreceptor replacement therapies aimed at photoreceptor regeneration in retinal disease.

Hypotrichosis and juvenile macular dystrophy caused by CDH3 mutation: A candidate disease for retinal gene therapy

Hypotrichosis with juvenile macular dystrophy (HJMD) is an autosomal recessive disorder that causes childhood visual impairment. HJMD is caused by mutations in CDH3 which encodes cadherin-3, a protein expressed in retinal pigment epithelium (RPE) cells that may have a key role in intercellular adhesion. We present a case of HJMD and analyse its phenotypic and molecular characteristics to assess the potential for retinal gene therapy as a means of preventing severe visual loss in this condition. Longitudinal in vivo imaging of the retina showed the relative anatomical preservation of the macula, which suggested the presence of a therapeutic window for gene augmentation therapy to preserve visual acuity. The coding sequence of CDH3 fits within the packaging limit of recombinant adeno-associated virus vectors that have been shown to be safe in clinical trials and can efficiently target RPE cells. This report expands the number of reported cases of HJMD and highlights the phenotypic characteristics to consider when selecting candidates for retinal gene therapy.

CNTF Gene Therapy Confers Lifelong Neuroprotection in a Mouse Model of Human Retinitis Pigmentosa

The long-term outcome of neuroprotection as a therapeutic strategy for preventing cell death in neurodegenerative disorders remains unknown, primarily due to slow disease progression and the inherent difficulty of assessing neuronal survival in vivo. Employing a murine model of retinal disease, we demonstrate that ciliary neurotrophic factor (CNTF) confers life-long protection against photoreceptor degeneration. Repetitive retinal imaging allowed the survival of intrinsically fluorescent cone photoreceptors to be quantified in vivo. Imaging of the visual cortex and assessment of visually-evoked behavioral responses demonstrated that surviving cones retain function and signal correctly to the brain. The mechanisms underlying CNTF-mediated neuroprotection were explored through transcriptome analysis, revealing widespread upregulation of proteolysis inhibitors, which may prevent cellular/extracellular matrix degradation and complement activation in neurodegenerative diseases. These findings provide insights into potential novel therapeutic avenues for diseases such as retinitis pigmentosa and amyotrophic lateral sclerosis, for which CNTF has been evaluated unsuccessfully in clinical trials.

Subretinal Visual Implant Alpha IMS--Clinical trial interim report

A subretinal visual implant (Alpha IMS, Retina Implant AG, Reutlingen, Germany) was implanted in 29 blind participants with outer retinal degeneration in an international multicenter clinical trial. Primary efficacy endpoints of the study protocol were a significant improvement of activities of daily living and mobility to be assessed by activities of daily living tasks, recognition tasks, mobility, or a combination thereof. Secondary efficacy endpoints were a significant improvement of visual acuity/light perception and/or object recognition (clinicaltrials.gov, NCT01024803). During up to 12 months observation time twenty-one participants (72%) reached the primary endpoints, of which thirteen participants (45%) reported restoration of visual function which they use in daily life. Additionally, detection, localization, and identification of objects were significantly better with the implant power switched on in the first 3 months. Twenty-five participants (86%) reached the secondary endpoints. Measurable grating acuity was up to 3.3 cycles per degree, visual acuities using standardized Landolt C-rings were 20/2000, 20/2000, 20/606 and 20/546. Maximal correct motion perception ranged from 3 to 35 degrees per second. These results show that subretinal implants can restore very-low-vision or low vision in blind (light perception or less) patients with end-stage hereditary retinal degenerations.

Fundus autofluorescence in the Abca4(-/-) mouse model of Stargardt disease--correlation with accumulation of A2E, retinal function, and histology

PURPOSE

To investigate fundus autofluorescence (AF) characteristics in the Abca4(-/-) mouse, an animal model for AMD and Stargardt disease, and to correlate findings with functional, structural, and biochemical assessments.

METHODS

Blue (488 nm) and near-infrared (790 nm) fundus AF images were quantitatively and qualitatively analyzed in pigmented Abca4(-/-) mice and wild type (WT) controls in vivo. Functional, structural, and biochemical assessments included electroretinography (ERG), light and electron microscopic analysis, and A2E quantification. All assessments were performed across age groups.

RESULTS

In Abca4(-/-) mice, lipofuscin-related 488 nm AF increased early in life with a ceiling effect after 6 months. This increase was first paralleled by an accumulation of typical lipofuscin granules in the retinal pigment epithelium (RPE). Later, lipofuscin and melanin granules decreased in number, whereas melanolipofuscin granules increased. This increase in melanolipofuscin granules paralleled an increase in melanin-related 790 nm AF. Old Abca4(-/-) mice revealed a flecked fundus AF pattern at both excitation wavelengths. The amount of A2E, a major lipofuscin component, increased 10- to 12-fold in 6- to 9-month-old Abca4(-/-) mice compared with controls, while 488 nm AF intensity only increased 2-fold. Despite pronounced lipofuscin accumulation in the RPE of Abca4(-/-) mice, ERG and histology showed a slow age-related thinning of the photoreceptor layer similar to WT controls up to 12 months.

CONCLUSIONS

Fundus AF can be used to monitor lipofuscin accumulation and melanin-related changes in vivo in mouse models of retinal disease. High RPE lipofuscin may not adversely affect retinal structure or function over prolonged time intervals, and melanin-related changes (melanolipofuscin formation) may occur before the decline in retinal function.

Cone photoreceptor neuroprotection conferred by CNTF in a novel in vivo model of battlefield retinal laser injury

PURPOSE

To develop a reproducible laboratory model to simulate a battlefield foveal laser injury and to test potential neuroprotective effects of a single injection treatment that might be administered in a military setting.

METHODS

Frequency-doubled 532-nm Nd:YAG laser was used to induce a threshold retinal injury bilaterally in transgenic reporter mice that have fluorescent cones. Intravitreal injection of ciliary neurotrophic factor (CNTF) was then administered to the lasered eye and compared with a contralateral sham injection of saline. The effect on fluorescent cone cell survival was quantified using a confocal scanning laser ophthalmoscope (cSLO), TUNEL assays, and quantitative real-time PCR (qPCR).

RESULTS

At 3 weeks post-laser, cSLO imaging showed that the proportion of surviving cones expressing green fluorescent protein (GFP) was greater in CNTF-treated (54.1 ± 5.15% of baseline count) than in sham-injected eyes (28.7 ± 4.4%), which was accompanied by a reduction in TUNEL-positive cells. This difference in cone survival persisted at the 6-week point (treated, 39.6 ± 3.2% versus sham, 18.0 ± 3.8%). These changes were accompanied by a reduction in TUNEL-positive cells. The Bcl-2/Bax ratio was increased in CNTF-treated eyes at 1 week postlaser exposure relative to controls.

CONCLUSIONS

A single intravitreal injection of CNTF protein was shown to improve cone survival when administered immediately after laser exposure. Similar treatments with CNTF might also have a role in attenuating retinal laser damage sustained by combat personnel in the military setting.

Assessment of tropism and effectiveness of new primate-derived hybrid recombinant AAV serotypes in the mouse and primate retina

Adeno-associated viral vectors (AAV) have been shown to be safe in the treatment of retinal degenerations in clinical trials. Thus, improving the efficiency of viral gene delivery has become increasingly important to increase the success of clinical trials. In this study, structural domains of different rAAV serotypes isolated from primate brain were combined to create novel hybrid recombinant AAV serotypes, rAAV2/rec2 and rAAV2/rec3. The efficacy of these novel serotypes were assessed in wild type mice and in two models of retinal degeneration (the Abca4(-/-) mouse which is a model for Stargardt disease and in the Pde6b(rd1/rd1) mouse) in vivo, in primate tissue ex-vivo, and in the human-derived SH-SY5Y cell line, using an identical AAV2 expression cassette. We show that these novel hybrid serotypes can transduce retinal tissue in mice and primates efficiently, although no more than AAV2/2 and rAAV2/5 serotypes. Transduction efficiency appeared lower in the Abca4(-/-) mouse compared to wild type with all vectors tested, suggesting an effect of specific retinal diseases on the efficiency of gene delivery. Shuffling of AAV capsid domains may have clinical applications for patients who develop T-cell immune responses following AAV gene therapy, as specific peptide antigen sequences could be substituted using this technique prior to vector re-treatments.

Assessment of 180° rotation of the choroid as a novel surgical treatment for age-related macular degeneration

PURPOSE

Our objective was to examine the feasibility of rotating choriocapillaris, Bruch's membrane (BM), and retinal pigment epithelium (RPE) through 180° on a vascular pedicle and to assess revascularization and tissue preservation postoperatively. Such an approach could be used in the treatment of age-related macular degeneration where there is focal disease at the macula with healthy tissues located peripherally.

METHODS

Successful surgery was performed in six rhesus macaque monkeys, which have a very similar choroidal blood supply to humans. After inducing a retinal detachment, the recurrent branch of the long posterior ciliary artery was used as a pedicle around which a graft stretching to the temporal equator was rotated. Retina was reattached over the rotated graft and eyes were followed up for up to 6 months with repeated angiography and optical coherence tomography (OCT). The morphology of retinal cells and BM were assessed by immunohistochemistry and electron microscopy.

RESULTS

Revascularization of the choroid was limited, with reestablishment of drainage to the vortex veins seen in only one case. There was a secondary loss of the RPE and outer retina evident on histological analysis three months after surgery. The underlying BM however remained intact.

CONCLUSIONS

Pedicled choroidal rotation surgery is technically feasible in vivo with intraoperative control of bleeding. However, lack of graft revascularization with the technique in its current form leads to neuroretinal and RPE tissue loss, and graft shrinkage. We found no evidence that rotational grafts are likely to improve the outcomes presently achieved with free graft techniques.

Optimization of in vivo confocal autofluorescence imaging of the ocular fundus in mice and its application to models of human retinal degeneration

PURPOSE

To investigate the feasibility and to identify sources of experimental variability of quantitative and qualitative fundus autofluorescence (AF) assessment in mice.

METHODS

Blue (488 nm) and near-infrared (790 nm) fundus AF imaging was performed in various mouse strains and disease models (129S2, C57Bl/6, Abca4(-/-), C3H-Pde6b(rd1/rd1), Rho(-/-), and BALB/c mice) using a commercially available scanning laser ophthalmoscope. Gray-level analysis was used to explore factors influencing fundus AF measurements.

RESULTS

A contact lens avoided cataract development and resulted in consistent fundus AF recordings. Fundus illumination and magnification were sensitive to changes of the camera position. Standardized adjustment of the recorded confocal plane and consideration of the pupil area allowed reproducible recording of fundus AF from the retinal pigment epithelium with an intersession coefficient of repeatability of ±22%. Photopigment bleaching occurred during the first 1.5 seconds of exposure to 488 nm blue light (∼10 mW/cm(2)), resulting in an increase of fundus AF. In addition, there was a slight decrease in fundus AF during prolonged blue light exposure. Fundus AF at 488 nm was low in animals with an absence of a normal visual cycle, and high in BALB/c and Abca4(-/-) mice. Degenerative alterations in Pde6b(rd1/rd1) and Rho(-/-) were reminiscent of findings in human retinal disease.

CONCLUSIONS

Investigation of retinal phenotypes in mice is possible in vivo using standardized fundus AF imaging. Correlation with postmortem analysis is likely to lead to further understanding of human disease phenotypes and of retinal degenerations in general. Fundus AF imaging may be useful as an outcome measure in preclinical trials, such as for monitoring effects aimed at lowering lipofuscin accumulation in the retinal pigment epithelium.

Characterization of a dominant cone degeneration in a green fluorescent protein-reporter mouse with disruption of Loci associated with human dominant retinal dystrophy

PURPOSE. To characterize anatomically and functionally the retinal degeneration observed in a transgenic mouse line (OPN1LW-EGFP) expressing enhanced green fluorescent protein (EGFP) in a subpopulation of cone photoreceptors, and to map the location of the transgenic insertion. METHODS. An anatomic comparison of cone survival was carried out between wild type (WT) and transgenic mice at three postnatal time points (P80, P140, and P245). Retinal function was assessed at P245 by ERG and included an ultraviolet flicker stimulus to isolate S-cone function. Chromosomal mapping by FISH and high-resolution mapping on DNA fibers (Fiber-FISH) were performed to identify the location of the transgenic insertion. RESULTS. GFP expression was largely absent in S-cones. Cone numbers were significantly reduced in OPN1LW-EGFP mice at all time points compared to WT, with cone loss independent of GFP expression. Anatomic loss correlated with a functional deficit in dark- and light-adapted ERG responses, including a reduction in UV-flicker response, confirming the degeneration of S-cones. The phenotype of heterozygote mice was slightly less severe than in homozygotes, consistent with a dominantly inherited cone dystrophy. The transgenic insertion mapped to a specific region on chromosome 10 orthologous with loci for progressive bifocal chorioretinal atrophy and North Carolina macular dystrophy on human chromosome 6. CONCLUSIONS. Cone loss is global in OPN1LW-EGFP mice and is independent of GFP expression. The mechanism underlying the degeneration remains elusive; however, disruption of loci associated with dominantly inherited retinal degenerations in humans makes this mouse of great interest.

Stem cells as a therapeutic tool for the blind: biology and future prospects

Retinal degeneration due to genetic, diabetic and age-related disease is the most common cause of blindness in the developed world. Blindness occurs through the loss of the light-sensing photoreceptors; to restore vision, it would be necessary to introduce alternative photosensitive components into the eye. The recent development of an electronic prosthesis placed beneath the severely diseased retina has shown that subretinal stimulation may restore some visual function in blind patients. This proves that residual retinal circuits can be reawakened after photoreceptor loss and defines a goal for stem-cell-based therapy to replace photoreceptors. Advances in reprogramming adult cells have shown how it may be possible to generate autologous stem cells for transplantation without the need for an embryo donor. The recent success in culturing a whole optic cup in vitro has shown how large numbers of photoreceptors might be generated from embryonic stem cells. Taken together, these threads of discovery provide the basis for optimism for the development of a stem-cell-based strategy for the treatment of retinal blindness.

Castration-induced hyperactivity of seminal vesicle in the catfish Clarias batrachus: a case of paradox and blockade by antiandrogen (cyproterone acetate) treatment

Castration of the catfish Clarias batrachus in late preparatory-early prespawning phase (April-May) caused time-dependent stimulatory effect on morphology, weight, and in the concentrations of biochemical correlates, such as total proteins, fructose, hexosamines and sialic acid in the seminal vesicle (SV). The peak changes were noticed on week 4 of castration. The hyperactivity was related to augmented production of testosterone by the SV of castrates with the levels significantly high from week 3 onwards. As a result, serum testosterone level fluctuated with a significant decrease in the first and fifth weeks, a significant increase in the third week, and no significant difference in the second and fourth weeks. Serum E2 level decreased significantly throughout. Cyproterone acetate treatment (CA; 1 mg/fish daily for 21 days) from the second day of castration decreased the size and weight of the SV and the concentrations of total proteins, hexosamines, fructose and sialic acid. The antiandrogen treatment did not alter serum testosterone level but the E2 level was significantly decreased. It is concluded that the hypersecretory activity of the SV in castrates is a sequel to local synthesis and action of testosterone and the effect could be prevented by CA by blocking androgen actions.