Deciphering the genetic architecture and ethnographic distribution of IRD in three ethnic populations by whole genome sequence analysis.

Patients with inherited retinal dystrophies (IRDs) were recruited from two understudied populations: Mexico and Pakistan as well as a third well-studied population of European Americans to define the genetic architecture of IRD by performing whole-genome sequencing (WGS). Whole-genome analysis was performed on 409 individuals from 108 unrelated pedigrees with IRDs. All patients underwent an ophthalmic evaluation to establish the retinal phenotype. Although the 108 pedigrees in this study had previously been examined for mutations in known IRD genes using a wide range of methodologies including targeted gene(s) or mutation(s) screening, linkage analysis and exome sequencing, the gene mutations responsible for IRD in these 108 pedigrees were not determined. WGS was performed on these pedigrees using Illumina X10 at a minimum of 30X depth. The sequence reads were mapped against hg19 followed by variant calling using GATK. The genome variants were annotated using SnpEff, PolyPhen2, and CADD score; the structural variants (SVs) were called using GenomeSTRiP and LUMPY. We identified potential causative sequence alterations in 61 pedigrees (57%), including 39 novel and 54 reported variants in IRD genes. For 57 of these pedigrees the observed genotype was consistent with the initial clinical diagnosis, the remaining 4 had the clinical diagnosis reclassified based on our findings. In seven pedigrees (12%) we observed atypical causal variants, i.e. unexpected genotype(s), including 4 pedigrees with causal variants in more than one IRD gene within all affected family members, one pedigree with intrafamilial genetic heterogeneity (different affected family members carrying causal variants in different IRD genes), one pedigree carrying a dominant causative variant present in pseudo-recessive form due to consanguinity and one pedigree with a de-novo variant in the affected family member. Combined atypical and large structural variants contributed to about 20% of cases. Among the novel mutations, 75% were detected in Mexican and 50% found in European American pedigrees and have not been reported in any other population while only 20% were detected in Pakistani pedigrees and were not previously reported. The remaining novel IRD causative variants were listed in gnomAD but were found to be very rare and population specific. Mutations in known IRD associated genes contributed to pathology in 63% Mexican, 60% Pakistani and 45% European American pedigrees analyzed. Overall, contribution of known IRD gene variants to disease pathology in these three populations was similar to that observed in other populations worldwide. This study revealed a spectrum of mutations contributing to IRD in three populations, identified a large proportion of novel potentially causative variants that are specific to the corresponding population or not reported in gnomAD and shed light on the genetic architecture of IRD in these diverse global populations.

Autoimmune retinopathy associated with monoclonal gammopathy of undetermined significance: a case report.

BACKGROUND: Monoclonal gammopathy of undetermined significance (MGUS) is a plasma cell dyscrasia and precursor to multiple myeloma. It has known ocular manifestations, but has not previously been shown to have an association with autoimmune retinopathy. CASE PRESENTATION: A 57 year-old female presented with 1 year of progressive, bilateral, peripheral vision loss, photopsias, and nyctalopia. Her fundus examination and extensive ancillary testing were concerning for hereditary versus autoimmune retinopathy. The patient was found to have anti-retinal antibodies against carbonic anhydrase II and enolase proteins with a negative genetic retinal dystrophy panel. Malignancy work-up was negative, but the patient was diagnosed with MGUS, a premalignant condition. The patient was treated with immunosuppressive therapies, with rituximab demonstrating the most robust therapeutic response with respect to patient symptoms and ophthalmic testing. CONCLUSIONS: MGUS should be considered as a potential etiology of autoimmune retinopathy in patients without other autoimmune or malignant disease processes. Immunosuppressive therapy may be helpful in limiting disease progression, with rituximab showing efficacy in retinopathy refractory to other agents.

IFT88 mutations identified in individuals with non-syndromic recessive retinal degeneration result in abnormal ciliogenesis.

Whole genome sequencing (WGS) was performed to identify the variants responsible for inherited retinal degeneration (IRD) in a Caucasian family. Segregation analysis of selected rare variants with pathogenic potential identified a set of compound heterozygous changes p.Arg266*:c.796C>T and p.Ala568Thr:c.1702G>A in the intraflagellar transport protein-88 (IFT88) gene segregating with IRD. Expression of IFT88 with the p.Arg266* and p.Ala568Thr mutations in mIMDC3 cells by transient transfection and in HeLa cells by introducing the mutations using CRISPR-cas9 system suggested that both mutations result in the formation of abnormal ciliary structures. The introduction of the IFT88 p.Arg266* variant in the homozygous state in HeLa cells by CRISPR-Cas9 genome-editing revealed that the mutant transcript undergoes nonsense-mediated decay leading to a significant depletion of IFT88 transcript. Additionally, abnormal ciliogenesis was observed in these cells. These observations suggest that the rare and unique combination of IFT88 alleles observed in this study provide insight into the physiological role of IFT88 in humans and the likely mechanism underlying retinal pathology in the pedigree with IRD.

ISCEV extended protocol for the photopic On-Off ERG.

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure, but encourages more extensive testing. This ISCEV extended protocol describes an extension to the ERG standard, namely the photopic On-Off ERG, and outlines common clinical applications. A light stimulus duration of 150-200 ms is used in the presence of a rod-suppressing background to elicit cone-driven On- and Off-system ERG components. The On-response occurs after the stimulus onset and has a negative a-wave and positive b-wave. The Off d-wave is a positive component evoked by stimulus offset. Common diagnoses that may benefit from additional photopic On-Off ERG testing include retinal dystrophies and retinal disorders that cause dysfunction at a level that is post-phototransduction or post-receptoral. On-Off ERGs assess the relative involvement of On- and Off-systems and may be of use in the diagnosis of disorders such as complete and incomplete congenital stationary night blindness (complete and incomplete CSNB), melanoma-associated retinopathy, and some forms of autoimmune retinopathy. The photopic On-Off ERGs may also be useful in X-linked retinoschisis, Batten disease, Duchenne muscular dystrophy, spinocerebellar degeneration, quinine toxicity, and other retinal disorders.

Contrast sensitivity deficits in patients with mutation-proven inherited retinal degenerations.

BACKGROUND: Patients with retinal diseases frequently complain of poor visual function even when visual acuity is relatively unaffected. This clinical finding has been attributed to deficits in contrast sensitivity (CS). The purpose of our study was to evaluate the CS in patients with clinical and genetic diagnosis of inherited retinal degeneration (IRD) and relatively preserved visual acuity. METHODS: Seventeen patients (30 eyes) with IRD and visual acuity of 20/40 or better, and 18 controls (18 eyes) without any ocular condition underwent slit lamp examination, visual acuity testing via standard Snellen chart testing, CS testing via the Quick Contrast Sensitivity Function (QCSF), and Spectral Domain Optical Coherence Tomography (SD-OCT). CS were measured at 1.0, 1.5, 3.0, 6.0, 12.0, and 18.0 cycles per degree (cpd). T tests with general estimated equations were used to compare CS between groups. Wald chi square followed by pairwise comparisons was used to compare CS between multiple groups. RESULTS: We included 12 patients with rod-cone dystrophy (RCD), 3 patients with Stargardt disease (STGD) and 2 patients with Best disease. Patients with IRD had significantly worse CS than controls (p < 0.001) in all spatial frequencies. Patients with STGD had more marked deficits in CS than patients with Best disease (p < 0.001) and RCD (p < 0.001) despite having similar visual acuities. CONCLUSION: Patients with IRD, especially patients with STGD with relatively preserved visual acuity have marked deficits in CS when measured across a range of spatial frequencies. We recommend that clinical trials for STGD incorporate CS measured over a range of spatial frequencies as a secondary clinical endpoint for monitoring visual function. CS may provide an explanation for complaints of visual dysfunction when visual acuity is not significantly altered.

Prolonged Inner Retinal Photoreception Depends on the Visual Retinoid Cycle.

In addition to rods and cones, mammals have inner retinal photoreceptors called intrinsically photosensitive retinal ganglion cells (ipRGCs), which use the photopigment melanopsin and mediate nonimage-forming visual responses, such as pupil reflexes and circadian entrainment. After photic activation, photopigments must be reverted to their dark state to be light-sensitive again. For rods and to some extent cones, photopigment regeneration depends on the retinoid cycle in the adjacent retinal pigment epithelium (RPE). By contrast, ipRGCs are far from the RPE, and previous work suggests that melanopsin is capable of light-dependent self-regeneration. Here, we used in vitro ipRGC recording and in vivo pupillometry to show that the RPE is required for normal melanopsin-based responses to prolonged light, especially at high stimulus intensities. Melanopsin-based photoresponses of rat ipRGCs were remarkably sustained when a functional RPE was attached to the retina, but became far more transient if the RPE was removed, or if the retinoid cycle was inhibited, or when Müller glia were poisoned. Similarly, retinoid cycle inhibition markedly reduced the steady-state amplitude of melanopsin-driven pupil reflexes in both mice and rats. However, melanopsin photoresponses in RPE-separated rat retinas became more sustained in the presence of an 11-cis-retinal analog. In conclusion, during prolonged illumination, melanopsin regeneration depends partly on 11-cis-retinal from the RPE, possibly imported via Müller cells. Implications for RPE-related eye diseases and the acne drug isotretinoin (a retinoid cycle inhibitor) are discussed. SIGNIFICANCE STATEMENT: Intrinsically photosensitive retinal ganglion cells (ipRGCs) contain the photopigment melanopsin and drive subconscious physiological responses to light, e.g., pupillary constriction and neuroendocrine regulation. In darkness, each photopigment molecule in ipRGCs, as well as rod/cone photoreceptors, contains 11-cis-retinal (a vitamin A derivative) and light isomerizes it to all-trans-retinal, which activates the photopigment. To make this photopigment excitable again,all-trans-retinal must be reisomerized to 11-cis-retinal. For rods and to some extent cones, this reisomerization occurs in the adjacent retinal pigment epithelium (RPE), but because ipRGCs are far from the RPE, they are thought to regenerate excitable melanopsin exclusively through RPE-independent means. Here, we present electrophysiological and behavioral evidence that ipRGCs depend on the RPE to continuously regenerate melanopsin during intense prolonged photostimulation.

Excess cones in the retinal degeneration rd7 mouse, caused by the loss of function of orphan nuclear receptor Nr2e3, originate from early-born photoreceptor precursors.

The orphan nuclear receptor NR2E3 is a direct transcriptional target of NRL, the key basic motif leucine zipper transcription factor that dictates rod versus cone photoreceptor cell fate in the mammalian retina. The lack of NR2E3 function in humans and in retinal degeneration rd7 mutant mouse leads to increased S-cones accompanied by rod degeneration, whereas ectopic expression of Nr2e3 in the cone-only Nrl(-/-) retina generates rod-like cells that do not exhibit any visual function. Using GFP to tag the newborn rods and by 5-bromo-2'-deoxyuridine birthdating, we demonstrate that early-born post-mitotic photoreceptor precursors in the rd7 retina express cone-specific genes. Transgenic mouse studies in the rd7 background show that Nr2e3 when expressed under the control of Crx promoter can restore rod photoreceptor function and suppress cone gene expression. Furthermore, Nr2e3 expression in photoreceptor precursors committed to be rods (driven by the Nrl promoter) could completely rescue the retinal phenotype of the rd7 mice. We conclude that excess of S-cones in the rd7 retina originate from photoreceptor precursors with a 'default' fate and not from proliferation of cones and that Nr2e3 is required to suppress the expression of S-cone genes during normal rod differentiation. These studies further support the 'transcriptional dominance' model of photoreceptor cell fate determination and provide insights into the pathogenesis of retinal disease phenotypes caused by NR2E3 mutations.

A CTRP5 gene S163R mutation knock-in mouse model for late-onset retinal degeneration.

Late-onset retinal macular degeneration (L-ORD) is an autosomal dominant inherited disorder caused by a single missense mutation (S163R) in the CTRP5/C1QTNF5 protein. Early phenotypic features of L-ORD include: dark adaptation abnormalities, nyctalopia, and drusen deposits in the peripheral macular region. Apart from posterior segment abnormalities, these patients also develop abnormally long anterior lens zonules. In the sixth decade of life the rod and cone function declines, accompanied by electroretinogram (ERG) abnormalities. Some patients also develop choroidal neovascularization and glaucoma. In order to understand the disease pathology and mechanisms involved in retinal dystrophy, we generated a knock-in (Ctrp5(+/-)) mouse model carrying the disease-associated mutation in the mouse Ctrp5/C1QTNF5 gene. These mice develop slower rod-b wave recovery consistent with early dark adaptation abnormalities, accumulation of hyperautofluorescence spots, retinal pigment epithelium abnormalities, drusen, Bruch's membrane abnormalities, loss of photoreceptors, and retinal vascular leakage. The Ctrp5(+/-) mice, which have most of the pathological features of age-related macular degeneration, are unique and may serve as a valuable model both to understand the molecular pathology of late-onset retinal degeneration and to evaluate therapies.

Gene Supplementation in Mice Heterozygous for the D477G RPE65 Variant Implicated in Autosomal Dominant Retinitis Pigmentosa.

The use of AAV-RPE65 vectors for gene supplementation has achieved spectacular success as a treatment for individuals with autosomal recessive retinal disease caused by biallelic mutations in the visual cycle gene RPE65. However, the efficacy of this approach in treating autosomal dominant retinitis pigmentosa (adRP) associated with a monoallelic mutation encoding a rare D477G RPE65 variant has not been studied. Although lacking a severe phenotype, we now find that knock-in mice heterozygous for D477G RPE65 (D477G KI mice) can be used to evaluate outcomes of AAV-RPE65 gene supplementation. Total RPE65 protein levels, which are decreased in heterozygous D477G KI mice, were doubled following subretinal delivery of rAAV2/5.hRPE65p.hRPE65. In addition, rates of recovery of the chromophore 11-cis retinal after bleaching were significantly increased in eyes that received AAV-RPE65, consistent with increased RPE65 isomerase activity. While dark-adapted chromophore levels and a-wave amplitudes were not affected, b-wave recovery rates were modestly improved. The present findings establish that gene supplementation enhances 11-cis retinal synthesis in heterozygous D477G KI mice and complement previous studies showing that chromophore therapy results in improved vision in individuals with adRP associated with D477G RPE65.

Establishing baseline rod electroretinogram values in achromatopsia and cone dystrophy.

PURPOSE: To establish the normal range of values for rod-isolated b-wave amplitudes in achromatopsia and cone dystrophies. METHODS: We reviewed charts of 112 patients with various types of cone dystrophy, and compared their standardized electroretinographic rod b-wave amplitudes with age-matched normal controls. Twenty-six patients had known mutations in achromatopsia and cone dystrophy genes, while 53 were characterized by their inheritance pattern since they had yet to have their gene identified. Visual acuity information and scotomata were documented. RESULTS: We found that patients with achromatopsia and cone dystrophy had rod b-wave amplitudes that were significantly lower than age-matched controls, but found no evidence of rod amplitude progression nor loss of peripheral visual fields in the study group. CONCLUSIONS: We found that cone dystrophy patients of all types had depressed rod-isolated ERGs across the board. If typical diagnostic criteria are used, these patients might be considered to have "abnormal" rod-isolated electroretinographic values, and might be called "cone-rod dystrophy", even though the waveforms are stable for years. Patients with cone-rod dysfunction patterns on ERG can be better understood by also performing kinetic (Goldmann) visual fields, which will help to distinguish cone dystrophies from progressive cone-rod dystrophies by central scotomata size and progression over time in many forms of cone-rod dystrophy.

Adherence and satisfaction in Argus II prosthesis users: a self determination theory model.

BACKGROUND: Self-determination theory (SDT) of human motivation was used to examine associations between different forms of motivation in Argus II retinal prosthesis users and their engagement and satisfaction with the Argus device. MATERIALS AND METHODS: Nine subjects were administered: 1) a Situational Motivation Scale (SIMS) questionnaire to measure intrinsic motivation, identified regulation, external regulation, and amotivation, and 2) the Argus questionnaire (AQ) which was organized into 5 categories to measure 'Decision to get an Argus implant,' 'Self-perception as an Argus user', 'Utility of Argus,' 'Perceived competence,' and 'Family support.' Spearman correlations (rs) were used to find associations between measures from SIMS and AQ. RESULTS: Nine subjects completed both questionnaires. Statistically significant associations were observed between identified regulation and AQ items from categories: Decision to get Argus, Self-perception, Utility of Argus, and Perceived competence; and between intrinsic motivation and AQ items from Self-perception and Utility. External regulation was negatively associated with Family support, and amotivation was associated with one item from Self-perception. Engagement with the device and satisfaction were associated to both identified regulation and intrinsic motivation. There was no significant relationship between external regulation and adherence to the device. CONCLUSIONS: The SDT model can be used to investigate the types of motivation that influence uptake and engagement of the Argus device. Clinicians can use this knowledge to improve outcomes by supporting confidence in users and by encouraging them to maintain internalization and continued commitment to adherence.

A Mouse Model with Ablated Asparaginase and Isoaspartyl Peptidase 1 (Asrgl1) Develops Early Onset Retinal Degeneration (RD) Recapitulating the Human Phenotype.

We previously identified a homozygous G178R mutation in human ASRGL1 (hASRGL1) through whole-exome analysis responsible for early onset retinal degeneration (RD) in patients with cone-rod dystrophy. The mutant G178R ASRGL1 expressed in Cos-7 cells showed altered localization, while the mutant ASRGL1 in E. coli lacked the autocatalytic activity needed to generate the active protein. To evaluate the effect of impaired ASRGL1 function on the retina in vivo, we generated a mouse model with c.578_579insAGAAA (NM_001083926.2) mutation (Asrgl1mut/mut) through the CRISPR/Cas9 methodology. The expression of ASGRL1 and its asparaginase activity were undetectable in the retina of Asrgl1mut/mut mice. The ophthalmic evaluation of Asrgl1mut/mut mice showed a significant and progressive decrease in scotopic electroretinographic (ERG) response observed at an early age of 3 months followed by a decrease in photopic response around 5 months compared with age-matched wildtype mice. Immunostaining and RT-PCR analyses with rod and cone cell markers revealed a loss of cone outer segments and a significant decrease in the expression of Rhodopsin, Opn1sw, and Opn1mw at 3 months in Asrgl1mut/mut mice compared with age-matched wildtype mice. Importantly, the retinal phenotype of Asrgl1mut/mut mice is consistent with the phenotype observed in patients harboring the G178R mutation in ASRGL1 confirming a critical role of ASRGL1 in the retina and the contribution of ASRGL1 mutations in retinal degeneration.

Intravitreal daptomycin: a safety and efficacy study.

PURPOSE: To determine the ocular toxicity of intravitreally injected daptomycin, a novel antibiotic for treatment of vancomycin-resistant organisms, and its efficacy in treating intraocular infection with coagulase-negative Staphylococcus epidermidis. METHODS: Four doses of intravitreal daptomycin were injected (75, 188, 375, and 750 µg) into 1 eye of Dutch belted rabbits (n = 3 per dose). Clinical examination, electroretinography, and histologic analysis were performed preinjection and 2 weeks after injection and compared with the fellow eye that received only intravitreal balanced salt solution. Experimental S epidermidis endophthalmitis was induced in Dutch belted rabbits (n = 24), and the ability of 200 µg of intravitreal daptomycin to result in culture-negative vitreous samples was measured at 24 hours and 48 hours. RESULTS: Seventy-five micrograms and 188 µg of daptomycin demonstrated acceptable safety profiles when injected intravitreally in Dutch belted rabbits. There was a dose-dependent increase in cataract formation, electroretinogram suppression, and photoreceptor damage with higher doses. Two hundred micrograms of intravitreal daptomycin resulted in near-complete vitreous sterilization 24 hours after treatment. Vitreous sterilization was complete by 48 hours. CONCLUSION: A dose of 200 µg of intravitreal daptomycin appears to be safe and efficacious in a rabbit model of bacterial endophthalmitis. Future investigations should focus on daptomycin as a therapeutic option for treating intraocular infection caused by vancomycin-resistant organisms.

Calculation of test-retest variability in phase I/IIa clinical trials for Inherited Retinal Degenerations.

Background: Several novel treatments of inherited retinal degenerations have undergone phase I/IIa clinical trials with limited sample size, yet investigators must still determine if toxicity or an efficacy signal occurred or if the change was due to test-retest variability (TRV) of the measurement tool.Materials and Methods: Synthetic datasets were used to compare three types of TRV estimators under different sample sizes, mean drift, skewness, and number of baseline measurements.Results: Mixed effects models underestimated the standard deviation of measurement error (SDEM); the unbiased change score estimator method (UBS) was more accurate. The fixed effect model had less bias and smaller standard deviation than UBS if >2 baseline measurements. The change score estimator had no bias; other estimators introduced bias for lower variability. With sample size <10, all estimators had high variance. With sample size ≥10, the differences between methods were often minimal. The pooled estimator model did not capture drift, whereas a fixed effect regression or mixed effects models accounted for drift while maintaining an accurate measure of variance. With small sample sizes, the bootstrap estimates of SDEM were severe underestimates, while the jackknife estimates were mildly low but much better. The jackknife was more accurate for the unbiased change score method than for the pooled estimator.Conclusions: The ideal phase I/IIa study has ≥20 subjects and uses UBS or its fixed effect model generalization if >2 baseline measurements. With non-ideal study parameters, investigators should at least quantify the error estimate present in their data analysis.

Age-related retinal degeneration (arrd2) in a novel mouse model due to a nonsense mutation in the Mdm1 gene.

We observed that a naturally occurring mouse strain developed age-related retinal degeneration (arrd2). These mice had normal fundi, electroretinograms (ERGs) and retinal histology at 6 months of age; vessel attenuation, RPE atrophy and pigmentary abnormalities at 14 months, which progressed to complete loss of photoreceptors and extinguished ERG by 22 months. Genetic analysis revealed that the retinal degeneration in arrd2 segregates in an autosomal recessive manner and the disease gene localizes to mouse chromosome 10. A positional candidate cloning approach detected a nonsense mutation in the mouse double minute-1 gene (Mdm1), which results in the truncation of the putative protein from 718 amino acids to 398. We have identified a novel transcript of the Mdm1 gene, which is the predominant transcript in the retina. The Mdm1 transcript is localized to the nuclear layers of neural retina. Expression of Mdm1 in the retina increases steadily from post-natal day 30 to 1 year, and a high level of Mdm1 are subsequently maintained. The Mdm1 transcript was found to be significantly depleted in the retina of arrd2 mice and the transcript was observed to degrade by nonsense-mediated decay. These results indicate that the depletion of the Mdm1 transcript may underlie the mechanism leading to late-onset progressive retinal degeneration in arrd2 mice. Analysis of a cohort of patients with age-related macular degeneration (AMD) wherein the susceptibility locus maps to chromosome 12q, a region bearing the human ortholog to MDM1, did not reveal association between human MDM1 and AMD.

Two mouse models for recoverin-associated autoimmune retinopathy.

PURPOSE: Recoverin has been demonstrated to be one of the main causative antigenic retinal proteins common in many cases of autoimmune retinopathy (AIR). Strategies for producing two different AIR mouse models associated with anti-recoverin antibodies were tested. METHODS: (1) Six-week-old female B6.MRL-Fal(lpr)/J mice (LPR) mice were immunized with recombinant recoverin three times at 2-4 week intervals. (2) Five-month-old Balb/cJ mice were injected with hybridoma cells designed to produce recoverin monoclonal antibodies. Anti-recoverin antibodies were analyzed by immunoblot and enzyme-linked immunosorbent assay (ELISA). Electroretinograms (ERG), histopathologic examination, and flow cytometric analysis were assessed. RESULTS: High anti-recoverin antibody levels were achieved in both models, accompanied by significantly reduced scotopic and photopic responses on the ERGs. Retinal histology showed swollen cell bodies in the inner nuclear layer in recoverin-immunized LPR mice, while photoreceptor and outer nuclear layer swelling was observed in recoverin hybridoma cells injected into balb/cJ mice. Glial fibrillary acidic protein (GFAP) staining detected a marked increase of Müller cells and astrocyte reactive gliosis in both mouse models. Rhodopsin and S-opsin staining was similar to controls, while decreased numbers of bipolar cells were observed in both models. Complement component C1q and C3 deposits increased upon immunohistopathologic retinal staining in both models, while increased numbers of CD4+ and CD68+ cells from retinas were found upon flow cytometric analysis. CONCLUSIONS: These two models had similar pathology in the retina, indicating the retinal antigens to recoverin antibody set off pathologic events that include leukocyte invasion, complement deposition, reactive gliosis in the retina, and selective retinal degeneration of inner nuclear layer neurons. These two AIR mouse models will allow for detailed pathologic investigation and testing of protein antigens associated with human AIR and can be used to test treatments. It is important to note that, since most AIR patients have multiple anti-retinal antibodies, it will be possible to study which antibodies are pathologic and which have no retinal pathologic effects. These models can also serve as an important research resource for studying the pathophysiology of specific retinal proteins by creating autoantibodies, which potentially will give a better understanding of retinal protein interactions.

Rapid visual field constriction in a patient with retinitis pigmentosa and pituitary adenoma.

PURPOSE: To report a case of pituitary adenoma in a patient with retinitis pigmentosa (RP) and consequent rapid constriction of the visual field in each eye, which is atypical for either of these pathologies. OBSERVATIONS: A 45-year old male, with a long-standing history of RP, presented with rapid vision loss over 3 months. Examination revealed a severe drop in visual acuity and significant progression of concentric visual field constriction in each eye compared to 3 months prior. MRI revealed a pituitary macroadenoma compressing the optic chiasm. The patient underwent endoscopic trans-sphenoidal resection of the tumor and experienced partial recovery of visual acuity but not visual field. CONCLUSIONS AND IMPORTANCE: The visual field deficit in this patient was atypical for pituitary adenoma or optic neuropathy. The pattern was most consistent with RP, but the rate of progression was not. In a patient with chiasmal pathology in the setting of pre-existing retinopathy, visual field progression may not be limited exclusively to the bitemporal regions. Rapid constriction of the visual field in a patient with RP should prompt a work-up for alternative etiologies which includes neuro-imaging.

X-Chromosome Inactivation Is a Biomarker of Clinical Severity in Female Carriers of RPGR-Associated X-Linked Retinitis Pigmentosa.

PURPOSE: X-linked retinitis pigmentosa can manifest in female carriers with widely variable severity, whereas others remain unaffected. The contribution of X-chromosome inactivation (XCI) to phenotypic variation has been postulated but not demonstrated. Furthermore, the impact of genotype and genetic modifiers has been demonstrated in affected males but has not been well established in female carriers. The purpose of this study was to describe the scope of clinical phenotype in female carriers with mutations in RPGR and quantify the contribution of genotype, genetic modifiers, and XCI to phenotypic severity. DESIGN: Cohort study. PARTICIPANTS: Seventy-seven female carriers with RPGR mutations from 41 pedigrees. METHODS: Coding single nucleotide polymorphisms were sequenced in candidate genetic modifier genes encoding known RPGR-interacting proteins. X-chromosome inactivation ratios were determined in genomic DNA isolated from blood (n = 42) and saliva (n = 20) using methylation status of X-linked polymorphic repeats. These genetic data were compared with disease severity based on quantitative clinical parameters. MAIN OUTCOME MEASURES: Visual acuity, Humphrey visual field (HVF) results, full-field electroretinography results, and dark adaptation. RESULTS: Most individuals at all ages were mildly affected or unaffected, whereas those who progressed to moderate or severe vision loss were older than 30 years. RPGR genotype was not associated with clinical severity. The D1264N variant in RPGRIP1L was associated with more severe disease. Skewed XCI toward inactivation of the normal RPGR allele was associated with more severe disease. The XCI ratio in both blood and saliva was a predictor of visual function as measured by HVF diameter, rod amplitude, flicker amplitude, and flicker implicit time. For carriers with extreme XCI skewing of 80:20 or more, 57% were affected severely compared with 8% for those with XCI of less than 80:20 (P = 0.002). CONCLUSIONS: Female carriers with mutations in RPGR demonstrate widely variable clinical severity. X-chromosome inactivation ratios correlate with clinical severity and may serve as a predictor of clinically significant disease. Because RPGR gene therapy trials are underway, a future imperative exists to determine which carriers require intervention and when to intervene. X-chromosome inactivation analysis may be useful for identifying candidates for early intervention.

The RUSH2A Study: Best-Corrected Visual Acuity, Full-Field Electroretinography Amplitudes, and Full-Field Stimulus Thresholds at Baseline.

Purpose: The purpose of this study was to evaluate baseline best corrected visual acuity (BCVA), full-field electroretinography (ERG), full-field stimulus thresholds (FST), and their relationship with baseline demographic and clinical characteristics in the Rate of Progression in Usher syndrome type 2 (USH2A)-related Retinal Degeneration (RUSH2A) multicenter study. Methods: Participants had Usher syndrome type 2 (USH2, N = 80) or autosomal recessive nonsyndromic retinitis pigmentosa (ARRP, N = 47) associated with biallelic variants in the USH2A gene. Associations of demographic and clinical characteristics with BCVA, ERG, and FST were assessed with regression models. Results: In comparison to ARRP, USH2 had worse BCVA (median 79 vs. 82 letters; P < 0.001 adjusted for age), lower rod-mediated ERG b-wave amplitudes (median 0.0 vs. 6.6 µV; P < 0.001) and 30 Hz flicker cone-mediated ERG amplitudes (median 1.5 vs. 3.1 µV; P = 0.001), and higher (white, blue, and red) FST thresholds (means [-26, -31, -23 dB] vs. [-39, -45, -28 dB]; P < 0.001 for all stimuli). After adjusting for age, gender, and duration of vision loss, the difference in BCVA between diagnosis groups was attenuated (P = 0.09). Only diagnosis was associated with rod- and cone-mediated ERG parameters, whereas both genders (P = 0.04) and duration of visual loss (P < 0.001) also were associated with FST white stimulus. Conclusions: USH2 participants had worse BCVA, ERG, and FST than ARRP participants. FST was strongly associated with duration of disease; it remains to be determined whether it will be a sensitive measure of progression. Translational Relevance: Using standardized research protocols in RUSH2A, measures have been identified to monitor disease progression and treatment response and differentiate features of prognostic relevance between USH2 and ARRP participants with USH2A mutations.

Advancing Clinical Trials for Inherited Retinal Diseases: Recommendations from the Second Monaciano Symposium.

Major advances in the study of inherited retinal diseases (IRDs) have placed efforts to develop treatments for these blinding conditions at the forefront of the emerging field of precision medicine. As a result, the growth of clinical trials for IRDs has increased rapidly over the past decade and is expected to further accelerate as more therapeutic possibilities emerge and qualified participants are identified. Although guided by established principles, these specialized trials, requiring analysis of novel outcome measures and endpoints in small patient populations, present multiple challenges relative to study design and ethical considerations. This position paper reviews recent accomplishments and existing challenges in clinical trials for IRDs and presents a set of recommendations aimed at rapidly advancing future progress. The goal is to stimulate discussions among researchers, funding agencies, industry, and policy makers that will further the design, conduct, and analysis of clinical trials needed to accelerate the approval of effective treatments for IRDs, while promoting advocacy and ensuring patient safety.