Targeting miR-181a/b in retinitis pigmentosa: implications for disease progression and therapy

BACKGROUND

Retinitis pigmentosa (RP) is a genetically heterogeneous group of degenerative disorders causing progressive vision loss due to photoreceptor death. RP affects other retinal cells, including the retinal pigment epithelium (RPE). MicroRNAs (miRs) are implicated in RP pathogenesis, and downregulating miR-181a/b has shown therapeutic benefit in RP mouse models by improving mitochondrial function. This study investigates the expression profile of miR-181a/b in RPE cells and the neural retina during RP disease progression. We also evaluate how miR-181a/b downregulation, by knocking out miR-181a/b-1 cluster in RPE cells, confers therapeutic efficacy in an RP mouse model and explore the mechanisms underlying this process.

RESULTS

Our findings reveal distinct expression profiles, with downregulated miR-181a/b in RPE cells suggesting a protective response and upregulated miR-181a/b in the neural retina indicating a role in disease progression. We found that miR-181a/b-2, encoded in a separate genomic cluster, compensates for miR-181a/b-1 ablation in RPE cells at late time points. The transient downregulation of miR-181a/b in RPE cells at post-natal week 6 (PW6) led to improved RPE morphology, retarded photoreceptor degeneration and decreased RPE aerobic glycolysis.

CONCLUSIONS

Our study elucidates the underlying mechanisms associated with the therapeutic modulation of miR-181a/b, providing insights into the metabolic processes linked to its RPE-specific downregulation. Our data further highlights the impact of compensatory regulation between miR clusters with implications for the development of miR-based therapeutics.

CRISPR editing of anti-anemia drug target rescues independent preclinical models of retinitis pigmentosa

Retinitis pigmentosa (RP) is one of the most common forms of hereditary neurodegeneration. It is caused by one or more of at least 3,100 mutations in over 80 genes that are primarily expressed in rod photoreceptors. In RP, the primary rod-death phase is followed by cone death, regardless of the underlying gene mutation that drove the initial rod degeneration. Dampening the oxidation of glycolytic end products in rod mitochondria enhances cone survival in divergent etiological disease models independent of the underlying rod-specific gene mutations. Therapeutic editing of the prolyl hydroxylase domain-containing protein gene (PHD2, also known as Egln1) in rod photoreceptors led to the sustained survival of both diseased rods and cones in both preclinical autosomal-recessive and dominant RP models. Adeno-associated virus-mediated CRISPR-based therapeutic reprogramming of the aerobic glycolysis node may serve as a gene-agnostic treatment for patients with various forms of RP.

The Peripapillary Retina - A Common Juncture in Stargardt Disease and Idiopathic Intracranial Hypertension

PURPOSE

To present the multimodal imaging and functional exam findings in a case of combined Stargardt disease and idiopathic intracranial hypertension.

METHODS

The patient was evaluated with multimodal imaging including color fundus photography, short wavelength autofluorescence, spectral domain optical coherence tomography as well as functional testing such as Humphrey visual fields and full-field electroretinogram.

RESULTS

A 35-year-old woman was referred for evaluation of bilateral transient visual obscurations over the course of 2 months. Optic disc edema was observed in both eyes as well as a bulls-eye maculopathy with pisciform flecks. Magnetic resonance imaging and subsequent lumbar puncture confirmed a diagnosis of idiopathic intracranial hypertension. Fundus autofluorescence demonstrated hyperautofluorescent flecks surrounding both the macula and the disc. Genetic testing and full-field electroretinogram confirmed a diagnosis of Stargardt disease. Notably, the peripapillary retina was not spared as is frequently seen in Stargardt disease, possibly due to the impact of disc edema in the area. The patient was treated with increasing doses of acetazolamide and familial testing for Stargardt disease was recommended.

CONCLUSION

Both Stargardt disease and idiopathic intracranial hypertension are separately rare diseases with common anatomic intersection at the peripapillary retina. Stargardt disease typically spares the peripapillary retina; however, in the present case shows some evidence of peripapillary involvement. This finding suggests some relationship between disc edema due to idiopathic intracranial hypertension and the natural history of Stargardt disease.

RBP3-Retinopathy-Inherited High Myopia and Retinal Dystrophy: Genetic Characterization, Natural History, and Deep Phenotyping

PURPOSE

To examine the genetic and clinical features and the natural history of RBP3-associated retinopathy.

DESIGN

Multi-center international, retrospective, case series of adults and children, with moleculraly confirmed RBP3-asociated retinopathy.

METHODS

The genetic, clinical, and retinal imaging findings, including optical coherence tomography (OCT) and fundus autofluorescence (FAF), were investigated both cross-sectionally and longitudinally. The results of international standard full-field electroretinography (ERG) and pattern electroretinography (PERG) were reviewed.

RESULTS

We ascertained 12 patients (5 female and 7 male) from 10 families (4 patients previously reported). Ten novel disease-causing RBP3 variants were identified. Ten patients were homozygous. The mean age (±SD, range) of the group was 21.4 years (±19.1, 2.9-60.5 years) at baseline evaluation. All 12 patients were highly myopic, with a mean spherical equivalent of -16.0D (range, -7.0D to -33.0D). Visual acuity was not significantly different between eyes, and no significant anisometropia was observed. Mean best-corrected visual acuity (BCVA) was 0.48 logMAR (SD, ±0.29; range, 0.2-1.35 logMAR); at baseline. Eleven patients had longitudinal BCVA assessment, with a mean BCVA of 0.46 logMAR after a mean follow-up of 12.6 years. All patients were symptomatic with reduced VA and myopia by the age of 7 years old. All patients had myopic fundi and features in keeping with high myopia on OCT, including choroidal thinning. The 4 youngest patients had no fundus pigmentary changes, with the rest of the patients presenting with a variable degree of mid-peripheral pigmentation and macular changes. FAF showed variable phenotypes, ranging from areas of increased signal to advanced atrophy in older patients. OCT showed cystoid macular edema at presentation in 3 patients, which persisted during follow-up in 2 patients and resolved to atrophy in the third patient. The ERGs were abnormal in 9 of 9 cases, revealing variable relative involvement of rod and cone photoreceptors with additional milder dysfunction post-phototransduction in some. All but 1 patient had PERG evidence of macular dysfunction, which was severe in most cases.

CONCLUSIONS

This study details the clinical and functional phenotype of RBP3-retinopathy in the largest cohort reported to date. RBP3-retinopathy is a disease characterized by early onset, slow progression over decades, and high myopia. The phenotypic spectrum and natural history as described herein has prognostic and counseling implications. RBP3-related disease should be considered in children with high myopia and retinal dystrophy.

A novel pathogenic CRB1 variant presenting as Leber Congenital Amaurosis 8 and evaluation of gene editing feasibility

INTRODUCTION

Leber Congenital Amaurosis (LCA) is an inherited retinal disease that presents in infancy with severely decreased vision, nystagmus, and extinguished electroretinography findings. LCA8 is linked to variants in the Crumbs homolog 1 (CRB1) gene.

CASE DESCRIPTION

We report a novel CRB1 variant in a 14-year-old male presenting with nystagmus, worsening vision, and inability to fixate on toys in his infancy. Color fundus photography revealed nummular pigments in the macula and periphery. Imaging studies revealed thickened retina on standard domain optical coherence tomography and widespread atrophy of the retinal pigment epithelium on autofluorescence. Full-field electroretinography revealed extinguished scotopic and significantly reduced photopic responses. Genetic testing demonstrated a novel homozygous variant, c.3057 T > A; p.(Tyr1019Ter), in the CRB1 gene. This variant is not currently amenable to base editing, however, in silico analysis revealed several potential prime editing strategies for correction.

CONCLUSION

This case presentation is consistent with LCA8, suggesting pathogenicity of this novel variant and expanding our knowledge of disease-causing CRB1 variants.

A New Preclinical Model of Retinitis Pigmentosa Due to Pde6g Deficiency

Purpose

Retinitis pigmentosa (RP) is the most common cause of inherited blindness, with onset occurring as early as 4 years of age in certain rare but severe forms caused by mutations in the gamma subunit of phosphodiesterase 6 (PDE6). Studies in humans and mice have shown that RP pathology begins with progressive photoreceptor death, which then drives changes in downstream neurons, neighboring retinal pigment epithelium (RPE), and vasculature. Here, we present the first detailed analysis of RP disease progression in Pde6g-deficient mice.

Design

Experimental study of an RP mouse model.

Subjects

We studied Pde6g^-/- and Pde6g^+/- mice at the age of 7, 16, 30, 44, and 56 days with n = 2 to 5 per group and time point.

Methods

Photoreceptor degeneration and retinal remodeling were analyzed in retinal sections by immunofluorescence. Retinal blood vessel degradation was analyzed in flat-mounted retinas immunolabeled for isolectin GS-IB4. Protein expression was measured by immunoblot. Acellular capillaries were assessed in trypsin-digested and hematoxylin-eosin-stained retinas at postnatal day (P) 44. Retinal pigment epithelium cells were delineated in flat-mounted RPE-choroid-sclera by immunolabeling for the cell-adhesion protein β-catenin.

Main Outcome Measures

Immunofluorescence and morphometry (quantitative analysis of outer nuclear layer, dendrite area, vessel area, acellular vessels, RPE cell size, number of nuclei per RPE cell, RPE cell eccentricity, and RPE cell solidity).

Results

This novel RP model exhibits early onset and rapid rod degeneration, with the vast majority gone by P16. This pathology leads to retinal remodeling, including changes of inner retinal neurons, early activation of glia cells, degradation of retinal vasculature, and structural abnormalities of the RPE.

Conclusions

The pathology in our Pde6g^-/- mouse model precisely mirrors human RP progression. The results demonstrate the significant role of the gamma subunit in maintaining phosphodiesterase activity and provide new insights into the disease progression due to Pde6g deficiency.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Venous Tortuosity in COL4A2-Associated Gould Syndrome

Mutations in collagen-encoding genes have been linked to numerous systemic diseases. Specifically, pathologic alterations in COL4A2 have been linked to Gould syndrome, a hereditary angiopathy affecting the brain, kidneys, and eyes. However, the ocular phenotype associated with COL4A2-associated disease has yet to be fully characterized. In this report, we describe a novel variant in COL4A2 identified in a 48-year-old woman and her 15-year-old daughter. Funduscopic examination demonstrated significant venous and arteriolar tortuosity. Genetic testing revealed a novel variant, c.2321G>A:p.(Gly774Glu), in COL4A2. This vascular phenotype is similar to the familial retinal arterial tortuosity seen in COL4A2-associated Gould syndrome with additional venous involvement. [Ophthalmic Surg Lasers Imaging Retina 2023;54:536-539.].

Translatability barriers between preclinical and clinical trials of AAV gene therapy in inherited retinal diseases

Inherited retinal diseases (IRDs) are progressive degenerative diseases which cause gradual vision loss or complete blindness. As over 270 gene mutations have been identified in the underlying pathology of IRDs, gene therapy as a treatment modality has been an increasingly active realm of investigation. Currently, the most common vehicle of ocular gene delivery is the adeno-associated virus (AAV) vector. This is injected into the immune-privileged subretinal space to mediate transgene expression in retinal cells. Although numerous animal models of IRDs have demonstrated successful outcomes following AAV-mediated gene delivery, many of these studies fail to translate into successful outcomes in clinical trials. The purpose of this review is to A) comparatively assess preclinical and clinical IRD trials in which the success of AAV-mediated therapy failed to translate between animal and human participants B) discuss factors which may complicate the translatability of gene therapy in animals to results in humans.

Primary versus Secondary Elevations in Fundus Autofluorescence

The method of quantitative fundus autofluorescence (qAF) can be used to assess the levels of bisretinoids in retinal pigment epithelium (RPE) cells so as to aid the interpretation and management of a variety of retinal conditions. In this review, we focused on seven retinal diseases to highlight the possible pathways to increased fundus autofluorescence. ABCA4- and RDH12-associated diseases benefit from known mechanisms whereby gene malfunctioning leads to elevated bisretinoid levels in RPE cells. On the other hand, peripherin2/RDS-associated disease (PRPH2/RDS), retinitis pigmentosa (RP), central serous chorioretinopathy (CSC), acute zonal occult outer retinopathy (AZOOR), and ceramide kinase like (CERKL)-associated retinal degeneration all express abnormally high fundus autofluorescence levels without a demonstrated pathophysiological pathway for bisretinoid elevation. We suggest that, while a known link from gene mutation to increased production of bisretinoids (as in ABCA4- and RDH12-associated diseases) causes primary elevation in fundus autofluorescence, a secondary autofluorescence elevation also exists, where an impairment and degeneration of photoreceptor cells by various causes leads to an increase in bisretinoid levels in RPE cells.

Development of a translatable gene augmentation therapy for CNGB1-retinitis pigmentosa

In this study, we investigate a gene augmentation therapy candidate for the treatment of retinitis pigmentosa (RP) due to cyclic nucleotide-gated channel beta 1 (CNGB1) mutations. We use an adeno-associated virus serotype 5 with transgene under control of a novel short human rhodopsin promoter. The promoter/capsid combination drives efficient expression of a reporter gene (AAV5-RHO-eGFP) exclusively in rod photoreceptors in primate, dog, and mouse following subretinal delivery. The therapeutic vector (AAV5-RHO-CNGB1) delivered to the subretinal space of CNGB1 mutant dogs restores rod-mediated retinal function (electroretinographic responses and vision) for at least 12 months post treatment. Immunohistochemistry shows human CNGB1 is expressed in rod photoreceptors in the treated regions as well as restoration of expression and trafficking of the endogenous alpha subunit of the rod CNG channel required for normal channel formation. The treatment reverses abnormal accumulation of the second messenger, cyclic guanosine monophosphate, which occurs in rod photoreceptors of CNGB1 mutant dogs, confirming formation of a functional CNG channel. In vivo imaging shows long-term preservation of retinal structure. In conclusion, this study establishes the long-term efficacy of subretinal delivery of AAV5-RHO-CNGB1 to rescue the disease phenotype in a canine model of CNGB1-RP, confirming its suitability for future clinical development.

Spatiotemporal control of genome engineering in cone photoreceptors

BACKGROUND

Cones are essential for color recognition, high resolution, and central vision; therefore cone death causes blindness. Understanding the pathophysiology of each cell type in the retina is key to developing therapies for retinal diseases. However, studying the biology of cone cells in the rod-dominant mammalian retina is particularly challenging. In this study, we used a bacterial artificial chromosome (BAC) recombineering method to knock in the "CreER^T2" sequence into the Gnat2 and Arr3 genes, respectively and generated three novel inducible CreER^T2 mice with different cone cell specificities.

RESULTS

These models (Gnat2^CreERT2, Arr3^T2ACreERT2, and Arr3^P2ACreERT2) express temporally controllable Cre recombinase that achieves conditional alleles in cone photoreceptors. Cre-LoxP recombination can be induced as early as postnatal day (PD) two upon tamoxifen injection at varying efficiencies, ranging from 10 to 15% in Gnat2^CreERT2, 40% in Arr3^T2ACreERT2, and 100% in Arr3^P2ACreERT2. Notably, knocking in the P2A-CreERT2 cassette does not affect cone cell morphology and functionality. Most cone-phototransduction enzymes, including Opsins, CNGA3, etc. are not altered except for a reduction in the Arr3 transcript.

CONCLUSIONS

The Arr3^P2ACreERT2 mouse, an inducible cone-specific Cre driver, is a valuable line in studying cone cell biology, function, as well as its relationship with rod and other retinal cells. Moreover, the Cre activity can be induced by delivering tamoxifen intragastrically as early as PD2, which will be useful for studying retinal development or in rapid degenerative mouse models.

Vitamin A deficiency and the retinal "double carrot" sign with optical coherence tomography

BACKGROUND

Spectral-domain optical coherence tomography (SD-OCT) and full-field electroretinography (ERG) allow retinal assessment with vitamin A deficiency (VAD). Using SD-OCT, this study aimed to characterize and follow a novel retinal abnormality in patients with VAD and intramuscular supplementation.

METHODS

Patients with VAD were retrospectively reviewed, including SD-OCT and electroretinography.

RESULTS

Three patients had VAD following bariatric or colon surgery and varying supplementation. All had nyctalopia, extinguished scotopic rod-specific function with ERG, and decreased serum vitamin A. None demonstrated surface abnormalities. All received intramuscular vitamin A with subjective resolution of symptoms. On SD-OCT, four of six eyes exhibited homogenous foveal hyperreflectivity anterior to retinal pigment epithelium-Bruch complex, reminiscent of a "double carrot", which improved following supplementation. ERG findings demonstrated improved scotopic rod-specific function in all cases; however, photopic function remained diminished in two cases.

CONCLUSIONS

Structural improvement of the proposed "double carrot" sign occurs soon after vitamin A supplementation. While scotopic function improves rapidly following supplementation, cone function recovers more slowly. Therefore, foveal changes such as the "double carrot" sign suggest that structural recovery of cones precedes functional recovery.

Monitoring Lesion Area Progression in Stargardt Disease: A Comparison of En Face Optical Coherence Tomography and Fundus Autofluorescence

Purpose

To compare longitudinal changes in en face spectral domain-optical coherence tomography (SD-OCT) measurements of ellipsoid zone (EZ) and retinal pigment epithelium (RPE) loss to changes in the hypoautofluorescent and hyperautofluorescent (AF) areas detected with short-wavelength (SW)-AF in ABCA4-associated retinopathy.

Methods

SD-OCT volume scans were obtained from 20 patients (20 eyes) over 2.6 ± 1.2 years (range 1-5 years). The EZ, and RPE/Bruch's membrane boundaries were segmented, and en face slab images generated. SubRPE and EZ slab images were used to measure areas of atrophic RPE and EZ loss. These were compared to longitudinal measurements of the hypo- and abnormal AF (hypoAF and surrounding hyperAF) areas.

Results

At baseline, the en face area of EZ loss was significantly larger than the subRPE atrophic area, and the abnormal AF area was significantly larger than the hypoAF area. The median rate of EZ loss was significantly greater than the rate of increase in the subRPE atrophic area (1.2 mm2/yr compared to 0.5 mm2/yr). The median rate of increase in the abnormal AF area was significantly greater than the increase in the hypoAF area (1.6 mm2/yr compared to 0.6 mm2/yr).

Conclusions

En face SD-OCT can be used to quantify changes in RPE atrophy and photoreceptor integrity. It can be a complementary or alternative technique to SW-AF with the advantage of monitoring EZ loss. The SW-AF results emphasize the importance of measuring changes in the hypo- and abnormal AF areas.

Translational Relevance

The findings are relevant to the selection of outcome measures for monitoring ABCA4-associated retinopathy.

Scleral Thickness in Autosomal Dominant Best Vitelliform Macular Dystrophy

PURPOSE

To investigate the posterior and equatorial scleral thickness in patients with autosomal dominant Best disease, a condition that has chronic subretinal fluid.

METHODS

Retrospective study involving patients with Best disease and age-matched controls. Participants were evaluated with contact B-scan ultrasonography and enhanced depth imaging optical coherence tomography to evaluate scleral thickness in the posterior pole and equator. Univariate analysis and generalized estimating equations were used.

RESULTS

Of 9 patients with genetically proven Best disease and 23 age-matched controls, there was no significant difference in the age or the gender proportion between groups. Subfoveal choroidal thickness and axial length were not significantly different between groups. Both posterior scleral (OD; 1.38mm vs. 0.89mm, P<.001 and OS; 1.39mm vs. 0.83mm, P<.001) and equatorial scleral (OD; 0.61mm vs. 0.42mm, P=.003, and OS; 0.55mm vs. 0.41mm, P=.017) thicknesses were much greater in cases as compared with controls. Multivariate analysis showed male sex and having Best disease were each significant predictors of posterior scleral thickness and Best disease was the sole significant predictor for equatorial scleral thickness.

CONCLUSION

BEST1 gene may have a developmental role leading to having a thicker sclera, influencing disease manifestation, and contributing to the accumulation of subretinal fluid in Best disease.

Insights Into PROM1-Macular Disease Using Multimodal Imaging

Purpose

To describe the features of genetically confirmed PROM1-macular dystrophy in multimodal images.

Methods

Thirty-six (36) eyes of 18 patients (5-66 years; mean age, 42.4 years) were prospectively studied by clinical examination and multimodal imaging. Short-wavelength autofluorescence (SW-AF) and quantitative fundus autofluorescence (qAF) images were acquired with a scanning laser ophthalmoscope (HRA+OCT, Heidelberg Engineering) modified by insertion of an internal autofluorescent reference. Further clinical testing included near-infrared autofluorescence (NIR-AF; HRA2, Heidelberg Engineering) with semiquantitative analysis, spectral domain-optical coherence tomography (HRA+OCT) and full-field electroretinography. All patients were genetically confirmed by exome sequencing.

Results

All 18 patients presented with varying degrees of maculopathy. One family with individuals affected across two generations exhibited granular fleck-like deposits across the posterior pole. Areas of granular deposition in SW-AF and NIR-AF corresponded to intermittent loss of the ellipsoid zone, whereas discrete regions of hypoautofluorescence corresponded with a loss of outer retinal layers in spectral-domain optical coherence tomography scans. For 18 of the 20 eyes, qAF levels within the macula were within the 95% confidence intervals of healthy age-matched individuals; nor was the mean NIR-AF signal increased relative to healthy eyes.

Conclusions

Although PROM1-macular dystrophy (Stargardt disease 4) can exhibit phenotypic overlap with recessive Stargardt disease, significantly increased SW-AF levels were not detected. As such, elevated bisretinoid lipofuscin may not be a feature of the pathophysiology of PROM1 disease. The qAF approach could serve as a method of early differential diagnosis and may help to identify appropriate disease targets as therapeutics become available to treat inherited retinal disease.

Phenotypic Variability of Retinal Disease Among a Cohort of Patients With Variants in the CLN Genes

Purpose

To describe the phenotype of CLN-associated retinal dystrophy in a subset of patients at the Columbia University Medical Center, United States, and the Hospital das Clínicas de Pernambuco, Brazil, in comparison to the published literature.

Methods

Eleven patients with confirmed biallelic variants in the CLN genes were evaluated via dilated fundus examination, clinical imaging, and full-field electroretinogram. A thorough literature search was conducted to determine previously published variants and associated phenotypes.

Results

Genetic testing confirmed the presence of variants in CLN3, CLN7/MFSD8, CLN8, and GRN/CLN11. Five novel variants were identified, and four novel phenotypes of previously published alleles were described. The phenotype differed among patients with variants in the same gene and sometimes among patients with the same allele.

Conclusions

Substantial phenotypic variability among variants in the CLN genes makes identification of genotype-phenotype or allele-phenotype correlations challenging. Further study is required to establish an extensive database for adequate patient counseling.

TRAP1 Is Expressed in Human Retinal Pigment Epithelial Cells and Is Required to Maintain their Energetic Status

Age-related macular degeneration (AMD) is the leading cause of severe vision loss and blindness in elderly people worldwide. The damage to the retinal pigment epithelium (RPE) triggered by oxidative stress plays a central role in the onset and progression of AMD and results from the excessive accumulation of reactive oxygen species (ROS) produced mainly by mitochondria. Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a mitochondrial molecular chaperone that contributes to the maintenance of mitochondrial integrity by decreasing the production and accumulation of ROS. The present study aimed to evaluate the presence and the role of TRAP1 in the RPE. Here, we report that TRAP1 is expressed in human adult retinal pigment epithelial cells and is located mainly in the mitochondria. Exposure of RPE cells to hydrogen peroxide decreases the levels of TRAP1. Furthermore, TRAP1 silencing increases intracellular ROS production and decreases mitochondrial respiratory capacity without affecting cell proliferation. Together, these findings offer novel insights into TRAP1 functions in RPE cells, opening possibilities to develop new treatment options for AMD.

HIF2α activation and mitochondrial deficit due to iron chelation cause retinal atrophy

Iron accumulation causes cell death and disrupts tissue functions, which necessitates chelation therapy to reduce iron overload. However, clinical utilization of deferoxamine (DFO), an iron chelator, has been documented to give rise to systemic adverse effects, including ocular toxicity. This study provided the pathogenic and molecular basis for DFO-related retinopathy and identified retinal pigment epithelium (RPE) as the target tissue in DFO-related retinopathy. Our modeling demonstrated the susceptibility of RPE to DFO compared with the neuroretina. Intriguingly, we established upregulation of hypoxia inducible factor (HIF) 2α and mitochondrial deficit as the most prominent pathogenesis underlying the RPE atrophy. Moreover, suppressing hyperactivity of HIF2α and preserving mitochondrial dysfunction by α-ketoglutarate (AKG) protects the RPE against lesions both in vitro and in vivo. This supported our observation that AKG supplementation alleviates visual impairment in a patient undergoing DFO-chelation therapy. Overall, our study established a significant role of iron deficiency in initiating DFO-related RPE atrophy. Inhibiting HIF2α and rescuing mitochondrial function by AKG protect RPE cells and can potentially ameliorate patients' visual function.

Effects of medications on hypoxia-inducible factor in the retina: A review

Hypoxia-inducible factor (HIF) plays a critical role in the mechanisms that allow cells to adapt to various oxygen levels in the environment. Specifically, HIF-1⍺ has shown to be widely involved in cellular repair, survival, and energy metabolism. HIF-1⍺ has also been found in increased levels in cancer cells, highlighting the importance of balance in the hypoxic response. Promoting HIF-1⍺ activity as a potential therapy for degenerative diseases and inhibiting HIF-1⍺ as a therapy for pathologies with overactive cell proliferation are actively being explored. Digoxin and metformin, HIF-1⍺ inhibitors, and deferoxamine and ⍺-ketoglutarate analogues, HIF-1⍺ activators, are being studied for application in age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. However, these same medications have retinal toxicities that must be assessed before implementation of therapeutic care. Herein, we highlight the duality of therapeutic and toxic potential of HIF-1⍺ that must be carefully assessed prior to its clinical application in retinal disorders.

Surgical Approach with Pars Plana Vitrectomy for Subretinal Gene Therapy

Gene therapy is emerging as a treatment for inherited diseases including retinitis pigmentosa. Through surgery, specifically with pars plana vitrectomy, the subretinal space can be accessed to directly administer this treatment. The goal herein is to provide an overview of this approach.

Generation of an Avian Myeloblastosis Virus (AMV) Reverse Transcriptase Prime Editor

Prime editing (PE) is a novel, double-strand break (DSB)-independent gene editing technology that represents an exciting avenue for the treatment of inherited retinal diseases (IRDs). Given the extensive and heterogenous nature of the 280 genes associated with IRDs, genome editing has presented countless complications. However, recent advances in genome editing technologies have identified PE to have tremendous potential, with the capability to ameliorate small deletions and insertions in addition to all twelve possible transition and transversion mutations. The current PE system is based on the fusion of the Streptococcus pyogenes Cas9 (SpCas9) nickase H840A mutant and an optimized Moloney murine leukemia virus (MMLV) reverse-transcriptase (RT) in conjunction with a PE guide RNA (pegRNA). In this study, we developed a prime editor based on the avian myeloblastosis virus (AMV)-RT and showed its applicability for the installation of the PRPH2 c.828+1G>A mutation in HEK293 cells.

Protocol for Indocyanine Green Angiography

Indocyanine green (ICG) angiography was first approved by the Food and Drug Administration for human use in the 1956. Prior to its use in chorioretinal angiograms, ICG was used to measure blood flow and track cardiac output. It was only in 1969 when two researchers, Kyuga Kogure and Earl Choromokos from the University of Miami, first used ICG to create more accurate angiograms. In the following years, researchers were able to hone the underlying science of this new form of angiography. As time passed and technology advanced, the application of ICG in clinical practice became widespread. Today ICG is used to diagnose and monitor the progression of retinal and choroidal diseases affecting millions of individuals across the globe. ICG utilizes the injection of indocyanine green dye into a patient's bloodstream to visualize abnormalities of the choroid and retina by evaluating choroidal circulation. ICG angiography is useful in the diagnosis and management of occult choroidal neovascularization in age-related macular degeneration and may be used in other inflammatory conditions with central serous chorioretinopathy. ICG angiography offers advanced imaging for improved monitoring and treatment of a wide variety of choroidal and retinal diseases.

Rod Photoreceptor-Specific Ablation of Metformin Target, AMPK, in a Preclinical Model of Autosomal Recessive Retinitis Pigmentosa

Retinal gene therapies have shown tremendous progress in the past decade, but the sheer number of disease-causing mutations makes their applicability challenging. In this study we test our hypothesis that retinitis pigmentosa-associated retinal degeneration can be prevented through AMP-activated protein kinase (AMPK)-associated metabolic pathway reprogramming using a gene-independent model of degeneration and rescue. We show that recue of photoreceptor structure and function is not achieved through our model of metabolic reprogramming. These results suggest that RP may not be treatable through AMPK pathway modulation-based therapies.

Prime Editing Strategy to Install the PRPH2 c.828+1G>A Mutation

Mutations in peripherin 2 (PRPH2) are associated with a spectrum of inherited retinal diseases (IRDs) including retinitis pigmentosa (RP) and macular degeneration. As PRPH2 is localized to cone and rod outer segments, mutations in PRPH2 lead the disorganization or absence of photoreceptor outer segments. Here, we report on a patient with PRPH2-linked RP who exhibited widespread RPE atrophy with a central area of macular atrophy sparing the fovea. In future studies, we plan to model the pathobiology of PRPH2-based RP using induced pluripotent stem cell (iPSC)-derived retinal organoids. To effectively model rare mutations using iPSC-derived retinal organoids, we first require a strategy that can install the desired mutation in healthy wild-type iPSC, which can efficiently generate well-laminated retinal organoids. In this study, we developed an efficient prime editing strategy for the installation of the pathogenic PRPH2 c.828+1 G>A splice-site mutation underlying our patient's disease.

Correlations of Full-Field Stimulus Threshold With Functional and Anatomical Outcome Measurements in Advanced Retinitis Pigmentosa

PURPOSE

To compare full-field stimulus (FST) threshold values to conventional functional and anatomical measures commonly used in clinical practice.

DESIGN

Cross-sectional study.

METHODS

Patients with retinitis pigmentosa with nondetectable electroretinogram rod-mediated responses and light-adapted 3.0 cd·s·m² 30-Hz flicker (LA 3.0 flicker) amplitudes of 15 mV or less were included in this study. The threshold values for blue, white, and red stimuli on FST were correlated with best-corrected visual acuity, LA 3.0 flicker amplitude and implicit times, length of the ellipsoid zone (EZ) band and thickness of outer nuclear layer measurements on optical coherence tomography, and the vertical and horizontal diameters of the autofluorescent ring on autofluorescence imaging.

RESULTS

Forty-two eyes of 21 patients were included in the study. The mean FST thresholds were -22.5 ± 15.5 dB, -17.6 ± 11.5 dB, and -12.7 ± 6.0 dB for the blue, white, and red stimuli, respectively. The threshold values for the 3 FST stimuli were significantly correlated with selected functional and anatomical outcome measures. Specifically, they were strongly correlated with LA 3.0 flicker amplitude and EZ band length measured on optical coherence tomography. Using linear regression, blue and white stimulus values on FST were found to be predictive of EZ band length (R² = 0.579 and 0.491, respectively), and the vertical (R² = 0.694 and 0.532, respectively) and horizontal (R² = 0.626 and 0.400, respectively) diameters of the hyperautofluorescent ring.

CONCLUSIONS

The significant correlations between FST and other clinical outcome measures highlight its potential as an adjunct outcome measure.

Visual Function Tests

Inherited retinal diseases (IRDs), including retinitis pigmentosa, have devastating consequences for the visual function of affected individuals. Chief among these are a gradual loss of visual field, visual acuity, and night vision (otherwise known as nyctalopia). These changes often occur slowly, over a course of decades. Objective modalities for assessing these many aspects of visual function are crucial, not only to the monitoring of disease progression but, in recent years, also to evaluating the efficacy or lack thereof of new therapeutic interventions in the setting of clinical trials. This chapter will provide descriptions of these valuable assessment modalities, alongside discussions of their advantages and limitations in the context of serving those afflicted by IRDs.

Analysis of CRB1 Pathogenic Variants Correctable with CRISPR Base and Prime Editing

The mouse and human retina contain three major Crumbs homologue-1 (CRB1) isoforms. CRB1-A and CRB1-B have cell-type-specific expression patterns making the choice of gene augmentation strategy unclear. Gene editing may be a viable alternative for the amelioration of CRB1-associated retinal degenerations. To assess the prevalence and spectrum of CRB1-associated pathogenic variants amenable to base and prime editing, we carried out an analysis of the Leiden Open Variation Database. Editable variants accounted for 54.5% for base editing and 99.8% for prime editing of all CRB1 pathogenic variants in the Leiden Open Variation Database. The 10 most common editable pathogenic variants for CRB1 accounted for 34.95% of all pathogenic variants, with the c.2843G>A, p.(Cys948Tyr) being the most common editable CRB1 variant. These findings outline the next step toward developing base and prime editing therapeutics as an alternative to gene augmentation for the amelioration of CRB1-associated retinal degenerations.

Generation of CRB1 RP Patient-Derived iPSCs and a CRISPR/Cas9-Mediated Homology-Directed Repair Strategy for the CRB1 c.2480G>T Mutation

Mutations in the Crumbs-homologue-1 (CRB1) gene lead to a spectrum of severe inherited retinal diseases, including retinitis pigmentosa (RP). The establishment of a genotype-phenotype correlation in CRB1 patients has been difficult due to the substantial variability and phenotypic overlap between CRB1-associated diseases. This phenotypic modulation may be due to several factors, including genetic modifiers, deep intronic mutations, isoform diversity, and copy number variations. Induced pluripotent stem cell (iPSC)-derived patient retinal organoids are novel tools that can provide sensitive, quantitative, and scalable phenotypic assays. CRB1 RP patient iPSC-derived retinal organoids have shown reproducible phenotypes compared to healthy retinal organoids. However, having genetically defined iPSC isogenic controls that take into account potential phenotypic modulation is crucial. In this study, we generated iPSC from an early-onset CRB1 patient and developed a correction strategy for the c.2480G>T, p.(Gly827Val) CRB1 mutation using CRISPR/Cas9-mediated homology-directed repair.

CRISPR Off-Target Analysis Platforms

The clustered regularly interspaced short palindromic repeats (CRISPR)-Caspase9 (Cas9) system provides a programmable technology that may be used to edit the eukaryotic genome and epigenome. CRISPR/Cas9 includes a guide RNA targeted to a gene of interest which hybridizes to a nucleotide sequence next to a protospacer-adjacent motif (PAM) which guides the Cas9 endonucleases to the target site for cleavage via double-strand breaks. A caveat of the CRISPR/Cas9 system is the creation of off-target double-strand breaks (DSBs) which may result in anomalous insertions, deletions, and translocations. Thus, assays for the sensitive detection and analysis of off-target editing are critical. Here, we describe currently available CRISPR technologies, CRISPR applications, and current analysis platforms to detect off-target effects including genome-wide, unbiased identification of DSBs enabled by sequencing (GUIDE-Seq), high-throughput genomic translocation sequencing (HTGTS), breaks labeling, enrichments on streptavidin and next-generation sequencing (BLESS), and in vitro nuclease-digested genome sequencing (Digenome-seq).

Prime Editing for the Installation and Correction of Mutations Causing Inherited Retinal Disease: A Brief Methodology

Inherited retinal diseases (IRDs) encompass a large heterogeneous group of rare blinding disorders whose etiology originates from mutations in the 280 genes identified to date. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) systems represent a promising avenue for the treatment of IRDs, as exemplified by FDA clinical trial approval of EDIT-101 (AGN-151587), which removes a deep intronic variant in the CEP290 gene that causes Leber congenital amaurosis (LCA) type 10. Prime editing is a novel double-strand break (DSB) independent CRISPR/Cas system which has the potential to correct all 12 possible transition and transversion mutations in addition to small deletions and insertions. Here, as a proof-of-concept study, we describe a methodology using prime editing for the in vitro installation and correction of the classical Pde6b^rd10 c.1678C > T (p.Arg560Cys) mutation which causes autosomal recessive retinitis pigmentosa (RP) in mice.

Metabolite Extraction from RPE Cells and Retinas Related to Retinitis Pigmentosa

The application of metabolomics in ophthalmology helps to identify new biomarkers and elucidate disease mechanisms in different eye diseases, as well as aiding in the development of potential treatment options. Extracting metabolites successfully is essential for potential further analysis using mass spectrometry. In this chapter, we describe how to extract metabolites from a variety of sources including (1) cells on a dish, (2) cell culture medium, and (3) tissues in vivo with and without stable isotope tracers. Samples prepared using this protocol are suitable for a range of downstream mass spectrometry analyses and are stable in solvent for weeks at -80 °C.

Culture of Human Retinal Explants for Ex Vivo Assessment of AAV Gene Delivery

Due to the clinically established safety and efficacy profile of recombinant adeno-associated viral (rAAV) vectors, they are considered the "go to" vector for retinal gene therapy. Design of a rAAV-mediated gene therapy focuses on cell tropism, high transduction efficiency, and high transgene expression levels to achieve the lowest therapeutic treatment dosage and avoid toxicity. Human retinal explants are a clinically relevant model system for exploring these aspects of rAAV-mediated gene delivery. In this chapter, we describe an ex vivo human retinal explant culture protocol to evaluate transgene expression in order to determine the selectivity and efficacy of rAAV vectors for human retinal gene therapy.

Etiology of Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a set of symptoms including tunnel vision, night blindness, and progressive vision loss, stemming from a very heterogeneous set of causes-it can result from a several different kinds of mutations (non-syndromic) in conjunction with other symptoms, as part of a larger syndrome (syndromic), or secondary to an organ system disease state (secondary RP). This chapter explores and elucidates these various causes of RP.

The Use of Optical Coherence Tomography in Evaluation of Retinitis Pigmentosa

Optical coherence tomography (OCT) is a noninvasive imaging technology that has gained widespread use in the evaluation of multiple retinal pathologies, including retinitis pigmentosa (RP). OCT allows for visualization of distinct retinal layers and the choroid and facilitates study of morphological features associated with RP. OCT can be used to detect and to track progression of RP, as well as to correlate structural findings with functional manifestations of the disease. This chapter provides a basic overview of OCT technology and details elements of importance in the use of OCT for diagnosis and assessment of progression of RP.

Use of the Medmont Dark-Adapted Chromatic Perimeter for Assessing Rod Function in Retinitis Pigmentosa

Medmont Dark-Adapted Chromatic (DAC) Perimeter enables efficient and quantifiable evaluation of rod-mediated (scotopic) vision. DAC tests rod function at multiple retinal locations, creating a topographical map of rod-mediated vision. These dynamic rod responses can be used as a functional marker to monitor disease progression and functional alterations in inherited retinal dystrophies, such as retinitis pigmentosa, Stargardt disease, cone-rod dystrophy, and choroideremia. In this chapter, we describe a protocol for the operation and analysis of the Medmont DAC in monitoring and assessing various retinal disorders.

Ophthalmic Fluorescein Angiography

Following its implementation in the 1960s, fluorescein angiography (FA) has become a widely used and reliable tool in the diagnosis of retinal and choroidal disorders. FA is an imaging modality utilized to examine the circulation of the retina and choroid. Here, we describe the process of obtaining fundus images with sodium fluorescein dye as a contrast agent. Using this methodology, ophthalmologists may examine the retinal and choroidal vasculature to diagnose a wide scope of retinal and choroidal diseases.

A pathogenic in-frame deletion-insertion variant in BEST1 phenocopies Stargardt disease

Here, we describe affected members of a 2-generation family with a Stargardt disease-like phenotype caused by a 2-base pair deletion insertion, c.1014_1015delGAinsCT;p.(Trp338_Asn339delinsCysTyr), in BEST1. The variant was identified by whole-exome sequencing, and its pathogenicity was verified through chloride channel recording using WT and transfected mutant HEK293 cells. Clinical examination of both patients revealed similar phenotypes at 2 different disease stages that were attributable to differences in their age at presentation. Hyperautofluorescent flecks along the arcades were observed in the proband, while the affected mother exhibited more advanced retinal pigment epithelium (RPE) loss in the central macula. Full-field electroretinogram testing was unremarkable in the daughter; however, moderate attenuation of generalized cone function was detected in the mother. Results from electrooculogram testing in the daughter were consistent with widespread dysfunction of the RPE characteristic of Best disease. Whole-cell patch-clamp recordings revealed a statistically significant decrease in chloride conductance of the mutant compared with WT cells. This report on a mother and daughter with a BEST1 genotype that phenocopies Stargardt disease broadens the clinical spectrum of BEST1-associated retinopathy.

Establishment of the iPSC line CUIMCi005-A from a patient with Stargardt disease for retinal organoid culture

Pathogenic variation in the ABCA4 gene is the underlying cause of Stargardt disease, the most common inherited retinal degeneration. We established an induced pluripotent stem cell line for retinal organoid research from a patient with mild disease features who is compound heterozygous for the frequent c.5882G>A (p.Gly1961Glu) missense variant and a c.4947delC (p.Glu1650Argfs*12) frameshift variant. Peripheral blood mononuclear cells were reprogrammed using a non-integrating Sendai virus approach. G-banded karyotyping was normal (46, XY) and mycoplasma testing was negative. Immunohistochemistry and RT-qPCR were performed to verify the expression of pluripotency and stemness markers (LIN28, NANOG, OCT4 and SOX2) and trilineage differentiation.

Three-year results of phase I retinal gene therapy trial for CNGA3-mutated achromatopsia: results of a non randomised controlled trial

AIMS

To determine long-term safety and efficacy outcomes of a subretinal gene therapy for CNGA3-associated achromatopsia. We present data from an open-label, nonrandomised controlled trial (NCT02610582).

METHODS

Details of the study design have been previously described. Briefly, nine patients were treated in three escalating dose groups with subretinal AAV8.CNGA3 gene therapy between November 2015 and October 2016. After the first year, patients were seen on a yearly basis. Safety assessment constituted the primary endpoint. On a secondary level, multiple functional tests were carried out to determine efficacy of the therapy.

RESULTS

No adverse or serious adverse events deemed related to the study drug occurred after year 1. Safety of the therapy, as the primary endpoint of this trial, can, therefore, be confirmed. The functional benefits that were noted in the treated eye at year 1 were persistent throughout the following visits at years 2 and 3. While functional improvement in the treated eye reached statistical significance for some secondary endpoints, for most endpoints, this was not the case when the treated eye was compared with the untreated fellow eye.

CONCLUSION

The results demonstrate a very good safety profile of the therapy even at the highest dose administered. The small sample size limits the statistical power of efficacy analyses. However, trial results inform on the most promising design and endpoints for future clinical trials. Such trials have to determine whether treatment of younger patients results in greater functional gains by avoiding amblyopia as a potential limiting factor.

Chorioretinal atrophy following voretigene neparvovec despite the presence of fundus autofluorescence

INTRODUCTION

Leber congenital amaurosis (LCA) type 2, due to disease-causing variants in RPE65, is characterized by severe visual loss in early infancy. Current treatments include voretigene neparvovec-rzyl (VN) for RPE65-associated LCA. Herein, we present the long-term follow-up of a patient treated with VN using quantitative autofluorescence (488 nm excitation).

CASE REPORT

A 9-year-old girl with a diagnosis of LCA with biallelic variants in RPE65 presented for evaluation. The patient underwent VN treatment at the age of 11. The patient returned to clinic at age of 19 at which time imaging revealed evidence of chorioretinal atrophy. Quantitative autofluorescence performed prior to gene therapy and at 6- and 8-year follow-up revealed a central area of fundus autofluorescence.

DISCUSSION

This case report demonstrates acquisition of fundus autofluorescence at 6- and 8-year follow-up despite the development of chorioretinal atrophy.

Therapeutic Gene Editing in Inherited Retinal Disorders

Since the development of CRISPR/Cas9 gene editing in 2012, therapeutic editing research has produced several phase 1-2a trials. Here we provide an overview of the mechanisms and applications of various gene-editing technologies including adeno-associated virus vectors, lentiviruses, CRISPR/Cas9 systems, base and prime editing, antisense oligonucleotides, short-hairpin RNAs, Cas13, and adenosine deaminase acting on RNA for the treatment of various inherited retinal diseases (IRDs). We outline the various stages of clinical trials using these technologies and the impacts they have made in advancing the practice of medicine.

Longitudinal Analysis of a Resolving Foveomacular Vitelliform Lesion in ABCA4 Disease

PURPOSE

To describe the longitudinal progression and phenotypic association of bilateral foveomacular vitelliform lesions in the setting of ABCA4 disease.

DESIGN

Case report and cross-sectional cohort study.

PARTICIPANTS

Nineteen patients with confirmed ABCA4 disease exhibiting an optical gap phenotype.

METHODS

Multimodal retinal imaging across multiple visits included autofluorescence imaging, spectral-domain OCT (SD-OCT), and OCT angiography. Electro-oculogram (EOG) and full-field electroretinogram testing results were analyzed. Exome sequencing was performed for diagnostic confirmation and the verification of other variations.

MAIN OUTCOME MEASURES

Light-peak-to-dark-trough ratio (Arden ratio) on EOG; thickness and en face maps of various retinal layers on SD-OCT; area measurements on 488- and 787-nm autofluorescence images; and the presence of variation in vitelliform-associated genes identified using exome sequencing.

RESULTS

A 25-year-old White man presented with bilateral central vision loss due to foveal lesions consisting of vitelliform fluid. The result of EOG testing was inconsistent with bestrophinopathy (Arden ratio = 1.62), and no generalized rod or cone dysfunction was detected on full-field electroretinogram. Exome sequencing identified the pathogenic variants c.5882G>A (p.(Gly1961Glu)) and c.4139C>T (p.(Pro1380Leu)) in ABCA4 and no other vitelliform-associated genes. Significant thinning and abnormal reflectivity of photoreceptor-attributable layers as well as near-infrared autofluorescence abnormalities were found in lesion-adjacent areas. Complete resorption of the vitelliform fluid occurred after 30 months, after which the optical gap lesions exhibited an enlarged and "cavitated" appearance. Phenotypic screening for additional cases from a large ABCA4 disease database (n = 602) identified 18 additional patients at various stages of optical gap lesion formation, most of whom harbored the c.5882G>A (p.(Gly1961Glu)) variant (P < 0.001), although none had apparent vitelliform fluid. At least 5 of the 18 (31.6%) patients exhibited optical gap lesions with the distinct "cavitated" appearance, whereas the lesions remained unperturbed in the other patients over the course of examination.

CONCLUSIONS

Foveomacular vitelliform deposition is a mechanistically congruent but rare manifestation of ABCA4 disease. Specifically, this disease phenotype may be clinically associated with the c.5882G>A (p.(Gly1961Glu)) allele and optical gap lesions.

Foveolar thickness as potential standardized structural outcome measurement in studies of Bietti crystalline dystrophy

Bietti crystalline dystrophy (BCD) is an ultra-rare orphan disorder that can lead to blindness. Because of the variable rates of progression of the disease, it is necessary to identify suitable outcome measurements for tracking progression in BCD. A retrospective analysis of patients with a clinical and genetic diagnosis of BCD was conducted. Four measurements of spectral domain-optical coherence tomography were compared to patients’ best corrected visual acuity. We observed that patients with higher measurements of foveolar thickness, choroidal thickness in the foveolar region, ellipsoid zone band length and the outer nuclear layer + area, had on average better visual acuity. Future studies are needed to validate the structural–functional correlations we observed in BCD and to propose a sensitive and clinically meaningful outcome measurement for tracking this rare, variable disease.

Clinical characteristics of high myopia in female carriers of pathogenic RPGR mutations: a case series and review of the literature

BACKGROUND

RPGR mutations are the most common cause of X-linked retinitis pigmentosa (XLRP). High myopia has been described as a very frequent feature among affected female carriers of XLRP. However, the clinical phenotype of female patients presenting with X-linked RPGR-related high myopia has not been well described.

MATERIALS AND METHODS

Retrospective case series of four female patients with RPGR mutations and a diagnosis of high myopia, who presented to two academic eye centers. Clinical data, including age, family history, visual acuity, refractive error, dilated fundus exam, fundus photography, optical coherence tomography, electroretinography, and results of genetic testing, were collected.

RESULTS

Three RPGR variants identified in the present study have not been previously associated with myopia in female carriers. One variant (c.2405_2406delAG, p.Glu802Glyfs *32) has been previously associated with a myopic phenotype in a female patient. Patients became symptomatic between the first and sixth decades of life. Myopia-associated tilted optic discs and posterior staphyloma were present in all patients. Two patients presented with intraretinal migration of the retinal pigment epithelium.

CONCLUSION

RPGR-related high myopia has been associated with mutations in exons 1-14 and ORF15 in heterozygous females. There is a wide range of visual function among carriers. Although the exact mechanism of RPGR-related high myopia is still unclear, continued molecular diagnosis and description of phenotypes remain a crucial step in understanding the impact of RPGR mutations on visual function in female XLRP carriers.

Long-term vitamin A supplementation in a preclinical mouse model for RhoD190N-associated retinitis pigmentosa

Retinitis pigmentosa (RP) is caused by one of many possible gene mutations. The National Institutes of Health recommends high daily doses of vitamin A palmitate for RP patients. There is a critical knowledge gap surrounding the therapeutic applicability of vitamin A to patients with the different subtypes of the disease. Here, we present a case report of a patient with RP caused by a p.D190N mutation in Rhodopsin (RHO) associated with abnormally high quantitative autofluorescence values after long-term vitamin A supplementation. We investigated the effects of vitamin A treatment strategy on RP caused by the p.D190N mutation in RHO by exposing Rhodopsin p.D190N (RhoD190N/+) and wild-type (WT) mice to experimental vitamin A-supplemented and standard control diets. The patient's case suggests that the vitamin A treatment strategy should be further studied to determine its effect on RP caused by p.D190N mutation in RHO and other mutations. Our mouse experiments revealed that RhoD190N/+ mice on the vitamin A diet exhibited higher levels of autofluorescence and lipofuscin metabolites compared to WT mice on the same diet and isogenic controls on the standard control diet. Vitamin A supplementation diminished photoreceptor function in RhoD190N/+ mice while preserving cone response in WT mice. Our findings highlight the importance of more investigations into the efficacy of clinical treatments like vitamin A for patients with certain genetic subtypes of disease and of genotyping in the precision care of inherited retinal degenerations.

Choroideremia Carriers: Dark-Adapted Perimetry and Retinal Structures

Purpose

In choroideremia (CHM) carriers, scotopic sensitivity was assessed by dark adapted chromatic perimetry (DACP) and outer retinal structure was evaluated by multimodal imaging.

Methods

Nine carriers (18 eyes) and 13 healthy controls (13 eyes) underwent DACP testing with cyan and red stimuli. Analysis addressed peripapillary (4 test locations closest to the optic disc), macular (52 locations), and peripheral (60 locations outside the macula) regions. Responses were considered to be rod-mediated when cyan relative to red sensitivity was >5 dB. Fundus imaging included spectral domain optical coherence tomography (SD-OCT), short-wavelength (SW-AF), near-infrared (NIR-AF), ultrawide-field (200 degrees) pseudocolor fundus imaging, and quantitative (qAF) fundus autofluorescence.

Results

Detection of the cyan stimulus was rod mediated in essentially all test locations (99.7%). In the macular and peripheral areas, DACP sensitivity values were not significantly different from healthy eyes. In the peripapillary area, sensitivities were significantly decreased (P < 0.05). SD-OCT imaging ranged from hyper-reflective lesions and discontinuities of the outer retinal bands to hypertransmission of signal. SW-AF and NIR-AF images presented with peripapillary atrophy in seven patients (14 eyes). Mosaicism was detectable in SW-AF images in seven patients and in NIR-AF images in five patients. Frank hypo-autofluorescence was visible in eight patients with distinct chorioretinopathy in seven patients. The qAF values were below the 95% confidence interval (CI) of healthy age-matched individuals in 12 eyes.

Conclusions

Rod mediated scotopic sensitivity was comparable to that in control eyes in macular and peripheral areas but was decreased in the peripapillary area where changes in retinal structure were also most severe.