Macular cystoid spaces in patients with retinal dystrophy

Nuclear Receptor Subfamily 2 Group E Member 3 (NR2E3): Role in Retinal Development and Disease

NR2E3 is a nuclear hormone receptor gene required for the correct development of the retinal rod photoreceptors. Expression of NR2E3 protein in rod cell precursors suppresses cone-specific gene expression and, in concert with other transcription factors including NRL, activates the expression of rod-specific genes. Pathogenic variants involving NR2E3 cause a spectrum of retinopathies, including enhanced S-cone syndrome, Goldmann-Favre syndrome, retinitis pigmentosa, and clumped pigmentary retinal degeneration, with limited evidence of genotype-phenotype correlations. A common feature of NR2E3-related disease is an abnormally high number of cone photoreceptors that are sensitive to short wavelength light, the S-cones. This characteristic has been supported by mouse studies, which have also revealed that loss of Nr2e3 function causes photoreceptors to develop as cells that are intermediate between rods and cones. While there is currently no available cure for NR2E3-related retinopathies, there are a number of emerging therapeutic strategies under investigation, including the use of viral gene therapy and gene editing, that have shown promise for the future treatment of patients with NR2E3 variants and other inherited retinal diseases. This review provides a detailed overview of the current understanding of the role of NR2E3 in normal development and disease, and the associated clinical phenotypes, animal models, and therapeutic studies.

Cystoid macular oedema without leakage in fluorescein angiography: a literature review

Cystoid macular oedema (CMO), which is defined as a macular thickening and cystic changes due to accumulation of fluid, could be asymptomatic and only diagnosed using paraclinical techniques. Fluorescein angiography (FA) and optical coherence tomography (OCT) are useful in detecting CMO in clinical practice. Non-leaking CMO, also known as angiographically silent CMO, is referred to as cases of CMO without leakage in fluorescein angiography. This type of CMO has been reported in some retinal dystrophies, in cases of maculopathy as a side effect of certain drugs, and also in some systemic disorders. The exact mechanism and treatment options for this type of CMO are still not clear. This literature review aims to discuss different causes of non-leaking CMO, proposed mechanisms, and management options. Three sections including drugs, retinal dystrophies, and systemic disorders are discussed in this review.

CRB1-Associated Retinal Dystrophies: Genetics, Clinical Characteristics, and Natural History

PURPOSE

To analyze the clinical characteristics, natural history, and genetics of CRB1-associated retinal dystrophies.

DESIGN

Multicenter international retrospective cohort study.

METHODS

Review of clinical notes, ophthalmic images, and genetic testing results of 104 patients (91 probands) with disease-causing CRB1 variants. Macular optical coherence tomography (OCT) parameters, visual function, fundus characteristics, and associations between variables were the main outcome measures.

RESULTS

The mean age of the cohort at the first visit was 19.8 ± 16.1 (median 15) years, with a mean follow-up of 9.6 ± 10 years. Based on history, imaging, and clinical examination, 26 individuals were diagnosed with retinitis pigmentosa (RP; 25%), 54 with early-onset severe retinal dystrophy / Leber congenital amaurosis (EOSRD/LCA; 52%), and 24 with macular dystrophy (MD; 23%). Severe visual impairment was most frequent after 40 years of age for patients with RP and after 20 years of age for EOSRD/LCA. Longitudinal analysis revealed a significant difference between baseline and follow-up best-corrected visual acuity in the 3 subcohorts. Macular thickness decreased in most patients with EOSRD/LCA and MD, whereas the majority of patients with RP had increased perifoveal thickness.

CONCLUSIONS

A subset of individuals with CRB1 variants present with mild, adult-onset RP. EOSRD/LCA phenotype was significantly associated with null variants, and 167_169 deletion was exclusively present in the MD cohort. The poor OCT lamination may have a degenerative component, as well as being congenital. Disease symmetry and reasonable window for intervention highlight CRB1 retinal dystrophies as a promising target for trials of novel therapeutics.

Cohen Syndrome: Novel VPS13B Genetic Variants in a Male Portuguese Patient with Pigmentary Retinopathy

The purpose of this clinical report was to describe a case of Cohen syndrome with its classical ophthalmological manifestations and novel VPS13B genetic variants. A 39-year-old Caucasian male patient with severe rod-cone retinal dystrophy and no history of parental consanguinity was referred to our ophthalmology department. Ophthalmologic history included high bilateral myopia and a 3-year prior bilateral cataract surgery. Systemic history included facial dysmorphism, intellectual disability, transient neutropenia, microcephaly, truncal obesity, and joint hyperextensibility. The patient presented classic fundoscopic features of pigmentary retinopathy in both eyes (OU). Optical coherence tomography (OCT) revealed bilateral central and diffuse retinal pigment epithelium (RPE) and outer retinal atrophy without concomitant macular edema, while fluorescein angiography (FA) demonstrated diffuse RPE atrophy with prominent choroidal vessels. The full-field ERG (ffERG) showed no dark-adapted or light-adapted responses and the P50 wave was not identified in the pattern ERG (pERG). The genetic study revealed two novel heterozygous variants in the VPS13B gene: (1) c.5138T>C p.(Leu1713Pro) and (2) c.10179del p.(Asn3393Lysfs*37), thus confirming the diagnosis of Cohen syndrome. This case report introduces these two novel genetic variants to the literature, in a patient with classic phenotypic characteristics of Cohen syndrome, a rare genetic disease which has been increasingly reported since its first description in 1973.

Identification of a novel CRB1 variant in a compound heterozygous state in a patient with CRB1-associated maculopathy and foveal retinoschisis

PURPOSE

To report a novel CRB1 variant responsible for autosomal recessive foveal retinoschisis and its associated clinical and electrophysiological data.

METHODS

A case report.

RESULTS

A 15-year-old boy has foveal retinoschisis similar to those seen in X-linked retinoschisis (XLRS). During follow-up, we observed the co-existence of foveoschitic changes and parafoveal macular atrophy. Molecular genetic testing identified compound heterozygous variants in the CRB1 gene, including a novel variant, c.3878 G > A, predicted to disrupt the normal translation of CRB1 and a previously reported likely pathogenic mutation, c.498_506del. Full-field electroretinograms (ERG) were normal but multifocal ERG showed focal reduced waveform amplitude corresponding to the area of atrophy.

CONCLUSIONS

A novel missense variant existing in a compound heterozygous state was identified. Biallelic CRB1 mutations can cause anatomical fovea disruption similar to XLRS but have very different electroretinogram findings. This case report enhances our understanding of the spectrum of biallelic CRB1 mutations.

Childhood cone-rod dystrophy with macular cyst formation in ABCA4 mutation identified by serial spectral-domain optical coherence tomography

Cone-rod dystrophy (CORD) is a type of progressive hereditary retinal dystrophies that causes cone predominant photoreceptor degeneration characterized by wide genotypic and phenotypic heterogeneity. Macular cyst (MC) occurs very infrequently in the pediatric age group and has rarely been described in CORD. We report a case of young-onset CORD that was affected by an isolated ABCA4 mutation complicated by the development of MC. Through serial spectral-domain ocular coherence tomography MC has been observed to persist for 24 months before its resolution, followed by retinal thinning and macular atrophy with corresponding visual acuity decline. The formation of MC and visual acuity appeared to be directly correlated in ABCA4-related CORD and its manifestation is invaluable in predicting eventual visual loss. We further speculate that dysfunctional outer blood-retinal barrier may play a role in the pathophysiology of MC development in CORD.

Development of retinal bullae in dogs with progressive retinal atrophy

OBJECTIVE

To report the development of focal bullous retinal detachments (bullae) in dogs with different forms of progressive retinal atrophy (PRA).

PROCEDURES

Dogs with three distinct forms of PRA (PRA-affected Whippets, German Spitzes and CNGB1-mutant Papillon crosses) were examined by indirect ophthalmoscopy and spectral domain optical coherence tomography (SD-OCT). Retinal bullae were monitored over time. One CNGB1-mutant dog was treated with gene augmentation therapy. The canine BEST1 gene coding region and flanking intronic sequence was sequenced in at least one affected dog of each breed.

RESULTS

Multiple focal bullous retinal detachments (bullae) were identified in PRA-affected dogs of all three types. They developed in 4 of 5 PRA-affected Whippets, 3 of 8 PRA-affected Germans Spitzes and 15 of 20 CNGB1-mutant dogs. The bullae appeared prior to marked retinal degeneration and became less apparent as retinal degeneration progressed. Bullae were not seen in any heterozygous animals of any of the types of PRA. Screening of the coding region and flanking intronic regions of the canine BEST1 gene failed to reveal any associated pathogenic variants. Retinal gene augmentation therapy in one of the CNGB1-mutant dogs appeared to prevent formation of bullae.

CONCLUSIONS

Retinal bullae were identified in dogs with three distinct forms of progressive retinal atrophy. The lesions develop prior to retinal thinning. This clinical change should be monitored for in dogs with PRA.

CNGB1-related rod-cone dystrophy: A mutation review and update

Cyclic nucleotide-gated channel β1 (CNGB1) encodes the 240-kDa β subunit of the rod photoreceptor cyclic nucleotide-gated ion channel. Disease-causing sequence variants in CNGB1 lead to autosomal recessive rod-cone dystrophy/retinitis pigmentosa (RP). We herein present a comprehensive review and analysis of all previously reported CNGB1 sequence variants, and add 22 novel variants, thereby enlarging the spectrum to 84 variants in total, including 24 missense variants (two of which may also affect splicing), 21 nonsense, 19 splicing defects (7 at noncanonical positions), 10 small deletions, 1 small insertion, 1 small insertion-deletion, 7 small duplications, and 1 gross deletion. According to the American College of Medical Genetics and Genomics classification criteria, 59 variants were considered pathogenic or likely pathogenic and 25 were variants of uncertain significance. In addition, we provide further phenotypic data from 34 CNGB1-related RP cases, which, overall, are in line with previous findings suggesting that this form of RP has long-term retention of useful central vision despite the early onset of night blindness, which is valuable for patient counseling, but also has implications for it being considered a priority target for gene therapy trials.

Novel clinical presentation of a CRX rod-cone dystrophy

We describe a novel clinical presentation of a CRX rod-cone dystrophy in a single family. Two boys ages 6 and 12 years presented with clinical and optical coherence tomography features suggestive of X-linked retinoschisis, but with optic nerve swelling without increased intracranial pressure. One patient had an electronegative electroretinogram (ERG) and the other had rod-cone dysfunction. Neither had retinoschisin (RS1) gene mutations. Biological mother and sister presented with retinal pigment epithelium (RPE) changes and abnormal cone-rod ERG responses. On further testing, next generation sequencing with array comparative genomic hybridisation showed a deletion in exon 4 of the CRX gene. Cystoid maculopathy in young male children can be difficult to distinguish from RS1-associated schisis. Phenotypic variants within a family must prompt a thorough retinal dystrophy evaluation even with electronegative ERG in the presenting child. This novel phenotype for CRX presents with optic nerve swelling and cystoid maculopathy in men, and RPE changes in women.

Coexistence of bilateral macular edema and pale optic disc in the patient with Cohen syndrome

Background

Cohen syndrome (Q87.8;ORPHA:193; OMIM#216550) is an autosomal recessive inherited genetic disorder caused by mutation in the VPS13B/COH1 gene. It is characterized by variable clinical symptoms such as deformity of the head, face, hands and feet, eye abnormalities, abdominal obesity, neutropenia and nonprogressive intellectual disability. The typical lesions in the eyeball in Cohen syndrome include high myopia, retinal dystrophy, strabismus, maculopathy and lens subluxation. The present study describes the coexistence of bilateral macular edema with pale optic disc in a patient with a homozygous deletion in the VPS13B/COH1 gene.

Material and methods

A 6-year-old Caucasian girl with facial dysmorphism, microcephaly, prominent upper incisors, narrow hands with slender fingers, congenital heart defect and ophthalmic symptoms was subjected to genetic testing. The genetic evaluation revealed a homozygous deletion on the long arm of chromosome 8 encompassing 20-25 exons of the VPS13 gene, as confirmed by Cohen syndrome. She underwent a full ophthalmological examination with the assessment of slit lamp examination of anterior segment and fundoscopy, refraction error, biometry, central corneal thickness and additionally electroretinography, optical coherence tomography and fundus photography.

Results

In the ophthalmologic examination, the girl had bilateral astigmatism accompanied by myopia and a marked reduction in central corneal thickness. Fundus examination showed pale optic nerve discs and "salt and pepper" retinopathy. Bilateral cystic macular edema was revealed in handheld optical coherence tomography. Electroretinography showed a reduced response amplitude of cones and rods.

Conclusion

In a patient with high myopia, macular edema, pale optic disc and facial dysmorphism, Cohen syndrome should be considered in the differential diagnosis. The severity of individual clinical features in patients with Cohen syndrome varies. It can be assumed that the type of mutation affects the occurrence and severity of individual symptoms.

Novel Pathogenic Sequence Variants in NR2E3 and Clinical Findings in Three Patients

A retrospective review of the clinical records of patients seen at the Oxford Eye Hospital identified as having NR2E3 mutations was performed. The data included symptoms, best-corrected visual acuity, multimodal retinal imaging, visual fields and electrophysiology testing. Three participants were identified with biallelic NR2E3 pathogenic sequence variants detected using a targeted NGS gene panel, two of which were novel. Participant I was a Nepalese male aged 68 years, and participants II and III were white Caucasian females aged 69 and 10 years old, respectively. All three had childhood onset nyctalopia, a progressive decrease in central vision, and visual field loss. Patients I and III had photopsia, patient II had photosensitivity and patient III also had photophobia. Visual acuities in patients I and II were preserved even into the seventh decade, with the worst visual acuity measured at 6/36. Visual field constriction was severe in participant I, less so in II, and fields were full to bright targets targets in participant III. Electrophysiology testing in all three demonstrated loss of rod function. The three patients share some of the typical distinctive features of NR2E3 retinopathies, as well as a novel clinical observation of foveal ellipsoid thickening.

Variable expressivity in patients with autosomal recessive retinitis pigmentosa associated with the gene CNGB1

PURPOSE

In a cohort of eight families (11 patients) with autosomal recessive retinitis pigmentosa (arRP), we clinically characterized disease associated with mutations in CNGB1.

METHODS

Visual function was determined by measuring the patients' visual acuity, dark- and light-adapted perimetry, and by full-field electroretinography. Retinal structure was evaluated with spectral-domain optical coherence tomography, fundus imaging, and autofluorescence imaging.

RESULTS

Age of onset ranged from 4 to 49 years (mean [SD] 26 [17], median 27 years). The age at visit was 27-54 years, mean 37 (17). The range of visual acuity was logMAR -0.1 to 1.3 (Snellen 20/16 to 20/400) in the right eye and -0.1 to 0.9 (Snellen 20/16 to 20/160) in the left eye. Electrophysiological testing in five patients showed an absence of the rod response. Cone responses ranged from normal to severely reduced. The patients exhibited loss of rod vision more severe than cone vision. Funduscopic images showed widespread retinal degeneration with pigment clumping, optic disk pallor, arteriole attenuation, and a peri-foveal ring of hyper autofluorescence. Three families were tested for olfactory dysfunction and results indicated mild to complete anosmia in individuals with mutations in CNGB1. Genetic analysis revealed 6 novel variants, c.2127 C > G, p.Phe709Leu; c.1431 C > A, p.Cys477*; c.2034 G > A, p.Trp678*; c.2092 T > C, p.Cys698Arg; and c.583 + 2 T > C, c.2305-34 G > A and 3 variants that have been previously described, c.2957A>T, p.Asn986Ile; c.2544dup, p.Leu849Alafs*3; and c.2492 + 1 G > A.

DISCUSSION

This is the first report for six novel CNGB1 variants associated with arRP. Two families had olfactory dysfunction in patients with arRP and family members who were heterozygous for a CNGB1 mutation. Additionally, findings demonstrated variable penetrance and expressivity of disease in these patients.

Optical coherence tomography findings in Cohen syndrome

Cohen syndrome is a rare disease that causes myopia and retinal degeneration in the setting of developmental delay and characteristic craniofacial features. We report optical coherence tomography (OCT) abnormalities in 4 patients with Cohen syndrome, 2 of whom have longitudinal follow-up. All subjects had schisis-like changes, with cystoid spaces in the inner retina as well as diffuse outer retinal atrophy sparing the subfoveal region. Ophthalmologic findings in 1 patient led to the work-up that resulted in a diagnosis of Cohen syndrome, suggesting that characteristic retinal abnormalities visualized by fundus examination and OCT may represent distinguishing features of this syndrome.

Intraretinal Cystoid Spaces in Regression of Punctate Inner Choroidopathy Lesions

PURPOSE

To describe and evaluate the intraretinal cystoid spaces (ICSs) in the eyes of punctate inner choroidopathy (PIC) patients.

METHODS

In this observational study, patients diagnosed with PIC were included and reviewed between December 2016 and November 2018. All patients underwent multimodal retinal imaging examinations.

RESULTS

Forty-one eyes of 26 patients diagnosed with PIC were included. ICSs were found in 13 eyes (31.7%) of 11 subjects. Statistical analysis revealed that except for spherical equivalent (P= .020), there were no significant difference between patients with ICSs and those with no ICSs at baseline. There were two types of ICSs according to the multimodal imaging findings. These two types of ICSs appeared with regressive PIC lesion and were stable during the follow-up period.

CONCLUSION

ICSs are commonly observed in PIC and they may be a sign of the restoration stage of the disease rather than a need for further clinical intervention.

A case of X-linked retinoschisis with atypical fundus appearance

PURPOSE

Mutations in the RS1 gene are known to cause retinoschisis, an X-linked hereditary retinal degeneration. Here, we present a case of atypical retinoschisis with clinical findings of retinoschisis and retinitis pigmentosa.

METHODS

This report is an observational case report. The detailed ophthalmological examinations included visual field determination, multimodal imaging and electrophysiological recordings. Targeted next-generation sequencing of a retinal disease gene panel was performed.

RESULTS

The 55-year-old male, highly hyperopic patient, presented with a best-corrected Snellen visual acuity of 20/100 in the right eye and 20/400 in the left eye. In the kinetic visual field, there was a superior scotoma, as well as a ring scotoma in the inferior hemisphere in the right eye and a concentric visual field constriction to 10° in the left eye. Funduscopy revealed marked pigmentary changes (i.e. bone spicules) in the mid-periphery bilaterally and symmetrically, as well as two small intra-retinal haemorrhages in the left eye. Full-field electroretinography recordings showed extinguished rod and cone responses. Diagnostic-genetic testing revealed a hemizygous missense mutation in the RS1 gene (c.305G > A; p.Arg102Gln) was identified.

CONCLUSION

We present a case of atypical retinoschisis with clinical findings of retinitis pigmentosa.

Ophthalmic manifestations of Heimler syndrome due to PEX6 mutations

BACKGROUND/AIMS

Pigmentary retinal dystrophy and macular dystrophy have been previously reported in Heimler syndrome due to mutations in PEX1. Here we reported the ocular manifestations in Heimler syndrome due to mutations in PEX6.

MATERIALS AND METHODS

Medical records were reviewed to identify patient demographics, ophthalmic and systemic findings, and results of diagnostic testing including whole genome sequencing.

RESULTS

Patient 1 is 12-year-old boy with a novel mutation c.275T>G (p.Val92Gly) and known mutation c.1802G>A (p.Arg601Gln) in PEX6. Patient 2 is a 7-year-old girl with the same known c.1802G>A (p.Arg601Gln) mutation and another novel missense mutation c.296G>T (p.Arg99Leu). Both patients exhibited a pigmentary retinopathy. Visual acuity in patient 1 was 20/80 and 20/25 following treatment of intraretinal cystoid spaces with carbonic anhydrase inhibitors, while patient 2 had visual acuity of 20/20 in both eyes without intraretinal cysts. Fundus autofluorescence showed a multitude of hyperfluorescent deposits in the paramacular area of both eyes. OCTs revealed significant depletion of photoreceptors in both patients and macular intraretinal cystoid spaces in one patient. Full field electroretinograms showed normal or abnormal photopic but normal scotopic responses. Multifocal electroretinograms were abnormal.

CONCLUSIONS

Heimler syndrome due to biallelic PEX6 mutations demonstrates a macular dystrophy with characteristic fundus autofluorescence and may be complicated by intraretinal cystoid spaces.

Nonleaking cystoid macular edema in Cohen syndrome

An 11-year-old girl with a history of neutropenia, developmental delay, hypotonia, and intellectual disability was diagnosed with Cohen syndrome after genetic testing discovered homozygous mutation in the VPS13B gene. She was referred to a retinal specialist with a chief complaint of decreased peripheral vision. On examination, decreased visual acuity, pigmentary changes, and nonleaking cystoid macular edema were present in both eyes.

Novel clinical findings in autosomal recessive NR2E3-related retinal dystrophy

PURPOSE

To evaluate the clinical phenotype of autosomal recessive NR2E3-related retinal dystrophy.

METHODS

We retrospectively studied 11 patients carrying out at least 2 NR2E3 mutations; they had undergone comprehensive ophthalmological examination, fundus photography, optical coherence tomography, electrophysiological testing, and visual field at the Regional Reference Center for Hereditary Retinal Degenerations of the Eye Clinic in Florence.

RESULTS

Five females and six males with a diagnosis of NR2E3-related retinal dystrophy were included in the study. All patients complained of nyctalopia. Visual acuity ranged from 0.00 logMAR to hand motion. Two patients presented bull's eye maculopathy, and one of these was characterized by a triple hyper-autofluorescent ring at the fundus autofluorescence examination. Three patients showed small yellowish dots and spots at the mid-periphery. One patient was characterized by widespread subretinal drusenoid deposits (SDD) at the posterior pole. Four patients showed vitreous abnormalities. Optical coherence tomography (OCT) examinations detected variable degrees of abnormal retinal lamination and schitic changes. Seven patients were compound heterozygous and four were homozygous for mutations in NR2E3.

CONCLUSIONS

Our study confirmed high variable phenotype in autosomal recessive NR2E3-related retinal dystrophy. Bull's eye maculopathy, subretinal drusenoid deposits, and foveal hypoplasia represent novel clinical findings in NR2E3-related retinal dystrophy. Macular involvement was detectable in all the patients, and the abnormal foveal avascular zone (FAZ) supports the role of NR2E3 in retinal development.

Quantitative and Qualitative Features of Spectral-Domain Optical Coherence Tomography Provide Prognostic Indicators for Visual Acuity in Patients With Choroideremia

BACKGROUND AND OBJECTIVE

To identify qualitative and quantitative features of spectral-domain optical coherence tomography (SD-OCT) as prognostic indicators of visual acuity (VA) loss in patients with choroideremia (CHM).

PATIENTS AND METHODS

Retrospective study of 57 male patients with CHM. Central foveal thickness (CFT), subfoveal choroidal thickness (SCT), fundus autofluorescence area, and evidence of outer retinal and choroidal degeneration were analyzed by SD-OCT.

RESULTS

Best-corrected VA logMAR at baseline was associated with CFT at baseline (r = -0.47; P < .01), CFT at most recent follow-up (r = -0.27; P < .01), and SCT at baseline (r = -0.31; P < .01). Ellipsoid zone (EZ) rupture was associated with a higher CFT loss (r = 0.33; P < .01) and macular cystic spaces (MCS) with a reduction in VA over time (hazard risk = 0.48; P = .05).

CONCLUSION

Reduced CFT at baseline, EZ rupture, and MCS are poor prognostic indicators for VA outcome. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:711-716.].

Molecular genetics and emerging therapies for retinitis pigmentosa: Basic research and clinical perspectives

Retinitis Pigmentosa (RP) is a hereditary retinopathy that affects about 2.5 million people worldwide. It is characterized with progressive loss of rods and cones and causes severe visual dysfunction and eventual blindness in bilateral eyes. In addition to more than 3000 genetic mutations from about 70 genes, a wide genetic overlap with other types of retinal dystrophies has been reported with RP. This diversity of genetic pathophysiology makes treatment extremely challenging. Although therapeutic attempts have been made using various pharmacologic agents (neurotrophic factors, antioxidants, and anti-apoptotic agents), most are not targeted to the fundamental cause of RP, and their clinical efficacy has not been clearly proven. Current therapies for RP in ongoing or completed clinical trials include gene therapy, cell therapy, and retinal prostheses. Gene therapy, a strategy to correct the genetic defects using viral or non-viral vectors, has the potential to achieve definitive treatment by replacing or silencing a causative gene. Among many clinical trials of gene therapy for hereditary retinal diseases, a phase 3 clinical trial of voretigene neparvovec (AAV2-hRPE65v2, Luxturna) recently showed significant efficacy for RPE65-mediated inherited retinal dystrophy including Leber congenital amaurosis and RP. It is about to be approved as the first ocular gene therapy biologic product. Despite current limitations such as limited target genes and indicated patients, modest efficacy, and the invasive administration method, development in gene editing technology and novel gene delivery carriers make gene therapy a promising therapeutic modality for RP and other hereditary retinal dystrophies in the future.