Comparison of Full-Field Stimulus Threshold Measurements in Patients With Retinitis Pigmentosa and Healthy Subjects With Dilated and Nondilated Pupil.

Purpose: The common protocol of full-field stimulus threshold (FST) testing recommends pupil dilation. The aim of this study is to investigate the difference between FST measurements with dilated and nondilated pupils in healthy subjects and patients with retinitis pigmentosa (RP). Methods: Twenty healthy subjects and 20 RP patients were selected. One pupil of each subject was dilated; the other eye was measured in physiological width of the pupil. The FST was conducted using Diagnosys Espion E2/E3 with white, blue, and red stimuli. Statistical analysis was conducted with a mixed-model analysis of variance and a paired t-test. Results: The statistical analysis revealed a significant difference between measurements of dilated and nondilated pupils with the following: blue stimuli for all subjects and groups except those with highly progressed RP; white stimuli for all tested subjects in total, for RP patients with better-preserved visual field (VF), and rod-mediated FST response; and red stimuli for RP patients with better-preserved VF and rod-mediated FST response. On average, the difference between the FST values for RP patients were -3.2 ± 3 dB for blue, -2.3 ± 2.9 dB for white, and -0.83 ± 3 dB for red stimuli. The correlation between the FST values of dilated and nondilated pupils with all three stimuli was linear. Conclusions: Current recommendations are to perform FST with dilated pupils. However, based on this study's findings, pupil dilation can be omitted for clinical diagnostics or rough follow-ups. Translational Relevance: Our data provide useful information for the clinical use of FST.

RPE65-Associated Retinal Dystrophies: Phenotypes and Treatment Effects with Voretigene Neparvovec.

Retinal dystrophies linked to the RPE65 gene are mostly fast-progressing retinal diseases, with childhood onset of night blindness and progressive visual loss up to the middle adult age. Rare phenotypes linked to this gene are known with congenital stationary night blindness or slowly progressing retinitis pigmentosa, as well as an autosomal dominant c.1430A>G (p.Asp477Gly) variant. This review gives an overview of the current knowledge of the clinical phenotypes, as well as experience with the efficacy and safety of the approved gene augmentation therapy voretigene neparvovec.

Simultaneous Pigmented Paravenous Retinochoroidal Atrophy and Retinitis Pigmentosa in the Contralateral Eye.

This case report describes a simultaneous diagnosis of paravenous retinochoroidal atrophy and retinitis pigmentosa in the same patient.

Evaluation of Full-Field Stimulus Threshold Test Results in Retinitis Pigmentosa: Relationship with Full-Field Electroretinography, Multifocal Electroretinography, Optical Coherence Tomography, and Visual Field.

Objectives: The full-field stimulus threshold (FST) test was developed to evaluate the efficacy and safety of treatments of hereditary retinal diseases. In this study we performed the FST test in patients with retinitis pigmentosa (RP) and compared the results with findings from other ophthalmological tests. Materials and Methods: The study included 51 intermediate and advanced RP patients and 21 normal subjects. All patients and controls underwent routine examination and ophthalmological tests including visual field, optical coherence tomography, full-field and multifocal electroretinography (mfERG), and FST tests. During FST testing, the perception thresholds of retina to the white, blue, and red FST were determined in decibels. Results: The mean age of the patients and the controls were 35.2 and 33.5 years, respectively. For all RP patients, no response was obtained on full-field ERG. All subjects were able to perform reliable FST tests. The mean values of visual acuity and central macular thickness were significantly lower and visual field mean deviation values were significantly higher in the RP group than the controls. When we evaluated the mfERG findings, the mean P1 wave amplitudes in all rings were significantly lower and the mean peak times were significantly longer in RP patients than controls. In comparisons of FST test results, the mean values for white, blue, red and the difference between blue-red thresholds were significantly lower in the RP group than the control group. Conclusion: The FST test is a fast and a reliable exam which can be done in subjects with poor visual acuity and reduced visual field. The results of this study confirm that the FST test can measure retinal sensitivity in severely affected RP subjects with flat flash ERG.

PHYH c.678+5G>T Leads to In-Frame Exon Skipping and Is Associated With Attenuated Refsum Disease.

Purpose: To investigate the molecular effect of the variant PHYH:c.678+5G>T. This variant has conflicting interpretations in the ClinVar database and a maximum allele frequency of 0.0045 in the South Asian population in gnomAD. Methods: We recruited patients from Moorfields Eye Hospital (London, UK) and Buenos Aires, Argentina, who were diagnosed with retinitis pigmentosa and found to have biallelic variants in PHYH, with at least one being c.678+5G>T. Total RNA was purified from PaxGene RNA-stabilized whole-blood samples, followed by reverse transcription to cDNA, PCR amplification of the canonical PHYH transcript, Oxford Nanopore Technologies library preparation, and single-molecule amplicon sequencing. Results: Four patients provided a blood sample. One patient had isolated retinitis pigmentosa and three had mild extraocular findings. Blood phytanic acid levels were normal in two patients, mildly elevated in one, and markedly high in the fourth. Retinal evaluation showed an intact ellipsoid zone as well as preserved autofluorescence in the macular region in three of the four patients. In all patients, we observed in-frame skipping of exons 5 and 6 in 31.1% to 88.4% of the amplicons and a smaller proportion (0% to 11.3% of amplicons) skipping exon 6 only. Conclusions: We demonstrate a significant effect of PHYH:c.678+5G>T on splicing of the canonical transcript. The in-frame nature of this may be in keeping with a mild presentation and higher prevalence in the general population. These data support the classification of the variant as pathogenic, and patients harboring a biallelic genotype should undergo phytanic acid testing.

Transcriptome alterations in sf3b4-depleted zebrafish: Insights into cataract formation in retinitis pigmentosa model.

Posterior subcapsular cataract (PSC) frequently develops as a complication in patients with retinitis pigmentosa (RP). Despite numerous scientific investigations, the intricate pathomechanisms underlying cataract formation in individuals affected by RP remain elusive. Therefore, our study aims to elucidate the potential pathogenesis of cataracts in an RP model using splicing factor subunit 3b (sf3b4) mutant zebrafish. By analyzing our previously published transcriptome dataset, we identified that, in addition to RP, cataract was listed as the second condition in our transcriptomic analysis. Furthermore, we confirmed the presence of nucleus retention in the lens fiber cells, along with abnormal cytoskeleton expression in both the lens fiber cells and lens epithelial cells in sf3b4-depleted fish. Upon closer examination, we identified 20 differentially expressed genes (DEGs) that played a role in cataract formation, with 95 % of them related to the downregulation of structural lens proteins. Additionally, we also identified that among all the DEGs, 13 % were associated with fibrotic processes. It seems that the significant upregulation of inflammatory mediators, in conjunction with TGF-ß signaling, plays a central role in the cellular biology of PSC and posterior capsular opacification (PCO) in sf3b4 mutant fish. In summary, our study provides valuable insights into cataract formation in the RP model of sf3b4 mutants, highlighting its complexity driven by changes in structural lens proteins and increased cytokines/growth factors.

RP1 Dominant p.Ser740* Pathogenic Variant in 20 Knowingly Unrelated Families Affected by Rod-Cone Dystrophy: Potential Founder Effect in Western Sicily.

Background and Objectives. Retinitis pigmentosa (RP) is the most common inherited rod-cone dystrophy (RCD), resulting in nyctalopia, progressive visual field, and visual acuity decay in the late stages. The autosomal dominant form (ADRP) accounts for about 20% of RPs. Among the over 30 genes found to date related to ADRP, RP1 pathogenic variants have been identified in 5-10% of cases. In a cohort of RCD patients from the Palermo province on the island of Sicily, we identified a prevalent nonsense variant in RP1, which was associated with ADRP. The objective of our study was to analyse the clinical and molecular data of this patient cohort and to evaluate the potential presence of a founder effect. Materials and Methods. From 2005 to January 2023, 84 probands originating from Western Sicily (Italy) with a diagnosis of RCD or RP and their relatives underwent deep phenotyping, which was performed in various Italian clinical institutions. Molecular characterisation of patients and familial segregation of pathogenic variants were carried out in different laboratories using Sanger and/or next-generation sequencing (NGS). Results. Among 84 probands with RCD/RP, we found 28 heterozygotes for the RP1 variant c.2219C>G, p.Ser740* ((NM_006269.2)*, which was therefore significantly prevalent in this patient cohort. After a careful interview process, we ascertained that some of these patients shared the same pedigree. Therefore, we were ultimately able to define 20 independent family groups with no traceable consanguinity. Lastly, analysis of clinical data showed, in our patients, that the p.Ser740* nonsense variant was often associated with a late-onset and relatively mild phenotype. Conclusions. The high prevalence of the p.Ser740* variant in ADRP patients from Western Sicily suggests the presence of a founder effect, which has useful implications for the molecular diagnosis of RCD in patients coming from this Italian region. This variant can be primarily searched for in RP-affected subjects displaying compatible modes of transmission and phenotypes, with an advantage in terms of the required costs and time for analysis. Moreover, given its high prevalence, the RP1 p.Ser740* variant could represent a potential candidate for the development of therapeutic strategies based on gene editing or translational read-through therapy for suppression of nonsense variants.

Novel hemizygous single-nucleotide duplication in RPGR in a patient with retinal dystrophy and sensorineural hearing loss.

BACKGROUND: The RPGR gene has been associated with X-linked cone-rod dystrophy. This report describes a variant in RPGR detected with exome sequencing (ES). Genes like RPGR have not always been included in panel-based testing and thus genome-wide tests such as ES may be required for accurate diagnosis. METHODS: The Texome Project is studying the impact of ES in medically underserved patients who are in need of genomic testing to guide diagnosis and medical management. The hypothesis is that ES could uncover diagnoses not made by standard medical care. RESULTS: A 58-year-old male presented with retinitis pigmentosa, sensorineural hearing loss, and a family history of retinal diseases. A previous targeted gene panel for retinal disorders had not identified a molecular cause. ES through the Texome Project identified a novel, hemizygous variant in RPGR (NM_000328.3: c.1302dup, p.L435Sfs*18) that explained the ocular phenotype. CONCLUSIONS: Continued genetics evaluation can help to end diagnostic odysseys of patients. Careful consideration of genes represented when utilizing gene panels is crucial to ensure an accurate diagnosis. Medically underserved populations are less likely to receive comprehensive genetic testing in their diagnostic workup. Our report is an example of the medical impact of genomic medicine implementation.

Mechanisms of cone sensitivity loss in retinitis pigmentosa.

PURPOSE: To explore the mechanisms of cone sensitivity loss in retinitis pigmentosa by combining two-colour perimetry with threshold versus intensity (tvi) testing. METHODS: Seven subjects with autosomal recessive retinitis pigmentosa and 10 normal subjects were recruited and underwent perimetric testing of one eye using 480- and 640-nm Goldman size V targets presented under scotopic conditions (no background illumination) and against a white background ranging in luminance from -1.5 to 2 log cd m-2 in 0.5 log cd m-2 steps. Data were fitted with tvi functions of the form logT = logT0 + log ((A + A0)/A0)n, where T is the threshold, T0 is the absolute threshold, A is the background intensity, A0 is the 'dark-light' constant and n is a gain constant. RESULTS: Reliable tvi functions could not be obtained within the region of the visual field corresponding to loss of the ellipsoid zone on optical coherence tomography. At fixation, changes in both T0 and A0 were observed, consistent with a d1 mechanism loss, which resulted in an upwards and rightwards shift of the tvi function. Losses at [±3°, ±3°] demonstrated changes in T0, consistent with a d3 mechanism loss, resulting in an upwards translation of the tvi curve. CONCLUSIONS: Although the absolute cone threshold was elevated at each location, shifts in the tvi function (so-called d1 mechanism loss) at fixation minimise threshold elevation in the presence of white adapting backgrounds, such as those typically employed in standard two-colour perimetry. At more peripheral testing locations, changes in threshold occurred independent of background luminance (so-called d3 mechanism loss). These findings suggest that backgrounds which selectively adapt rods while maintaining cones at, or near, absolute threshold may be preferable to conventional two-colour perimetry for assessing loss of cone sensitivity, especially at the point of fixation.

Transpalpebral electrical stimulation for the treatment of retinitis pigmentosa: study protocol for a series of N-of-1 single-blind, randomized controlled trial.

BACKGROUND: Retinitis pigmentosa (RP) is an inherited disease characterized by a progressive loss of rod photoreceptors of the eye, leading to irreversible blindness. To date, to our knowledge, no clinical prospective studies have been undertaken that could document the effect of interventions that could reverse or reduce the progression of this disease. The application of microcurrent stimulation (ES) of the eye in the treatment of chronic eye diseases such as glaucoma and age-related macular degeneration has been used over several decades and has been reported to have beneficial effects to reduce the progression of these blinding diseases and has been supported by animal studies and smaller clinical studies, but to date, no large randomized clinical trials on the use of microcurrent therapy have been published. More recent clinical reports have also shown beneficial effects of ES on slowing the progression of RP but also lacks data from robust prospective clinical outcome studies. To our knowledge, this is the first prospective randomized study to evaluate the safety and clinical effectiveness of transpalpebral electrical stimulation (TpES) on the progression of RP. METHODS: Randomized prospective study using N-of-1 trial 3 single-blind, crossover comparisons. The intervention period of each comparison is divided into treatment period and control period which are randomized arranged. Twelve participants will be strictly recruited in N-of-1 trial by the researcher in accordance with the inclusion and exclusion criteria. The main outcome of interest examined after each cycle of the 8-week intervention period is the assessment of the visual field (VF). Other variables of interest are best corrected visual acuity (BCVA), retinal function using electroretinogram (ERG), and visual function using NEI VFQ-25 questionnaire. Objective assessments of retinal changes will be undertaken using optical coherence tomography (OCT) and fundus autofluorescence (FAF). DISCUSSION: The trial will evaluate the efficacy and safety of microcurrent stimulation on RP and provide high-quality evidence for clinical application through N-of-1 trial. TRIAL REGISTRATION: Chinese Clinical Trial Registry; ChiCTR2300067357; https://www.chictr.org.cn/showproj.html?proj=174635 . Registered on 5 January 2023.

PHARC syndrome which an ultra-rare syndrome with retinitis pigmentosa and cataracts: case report and review of the literature.

BACKGROUND: PHARC syndrome (MIM:612674) is a rare neurodegenerative disorder characterized by demyelinating polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataracts (PHARC). The syndrome is caused by mutations in the ABHD12 gene, which encodes αß-hydrolase domain-containing protein 12 related to endocannabinoid metabolism. PHARC syndrome is one of the rare diseases; so far, only 51 patients have been reported in the literature. METHODS: We evaluated the 25-year-old male patient referred to us due to vision loss, cataracts, and hearing loss. Ophthalmological examinations and genetic analyses were performed using targeted next-generation sequencing. RESULTS: In the genetic analysis, the patient was diagnosed with PHARC syndrome by detecting homozygous (NM_001042472.3): c.871del (p.Tyr291IlefsTer28) novel pathogenic variation in the ABHD12 gene. Following the molecular diagnosis, he was referred to the neurology department for reverse phenotyping and sensorimotor demyelinating polyneuropathy was detected in the neurological evaluation. CONCLUSIONS: In this study, we report a novel variation in ABHD12 gene in the first Turkish-origin PHARC patient. We present this study to contribute genotype-phenotype correlation of PHARC syndrome and emphasize the importance of molecular genetic diagnosis in order to determine the appropriate clinical approach. This report is essential for expanding the phenotypic spectrum in different populations and understanding the genotype-phenotype correlation of PHARC syndrome via novel pathogenic variation in the ABHD12 gene.

Mutation analysis of RHO in patients with non-syndromic retinitis pigmentosa.

PURPOSE: To identify RHO mutations in patients with non-syndromic retinitis pigmentosa (NS-RP). METHODS: A total of 143 probands (46 family history and 97 sporadic cases) with NS-RP were recruited from Southeast China. The coding exons and adjacent intronic regions of RHO were PCR-amplified and sequenced by Sanger sequencing. The candidate variant was evaluated by the guidelines of American College of Medical Genetics and further validated through co-segregation analysis within the family. RESULTS: Five heterozygous mutations in RHO were detected in 5 out of 143 probands, where the frequency of RHO mutations in our cohort was approximately 3.5% (5/143) and 10.8% (5/46) for probands and families with NS-RP, respectively. Three known disease-causing mutations including c.C1030T (p.Q344X), c.C173G (p.T58R), and c.G266A (p.G89D) were identified in three unrelated families. The other two previously unreported mutations c.557C>A (p.S186X) and c.944delA (p.N315TfsX43) were confirmed in Family RP-087 and Family RP-139, respectively. These mutations co-segregated with available affected individuals in each family were not observed in the unaffected family members or in the 112 unrelated controls. CONCLUSIONS: This report expands the mutational spectrum of RHO gene associated with NS-RP and demonstrates the frequency of RP RHO mutations in Southeast Chinese populations.

Syndromic retinitis pigmentosa caused by biallelic SCAPER frameshift variant.

PURPOSE: Mutations in the SCAPER gene have previously been reported to be a rare cause of syndromic and non-syndromic autosomal recessive retinitis pigmentosa (RP). We report a case of syndromic RP caused by a frameshift heterozygous mutation in SCAPER. Our case has a relatively mild ocular phenotype with the presence of cone involvement noted on full field electroretinogram (ffERG) without impacting central or color vision. MATERIALS AND METHODS: A 17-year-old male presented with progressive nyctalopia in both eyes. He underwent ophthalmic examination and multimodal imaging. A complete retinal degeneration panel consisting of 322 genes was used to screen for molecular causes of retinal dystrophy in this patient along with family segregation analysis. RESULTS: Fundus examination of the proband revealed mild RP phenotype with waxy pallor of optic discs, attenuated retinal arterioles, and single bone spicule like pigmentary change in the mid-periphery bilaterally. Multimodal imaging and ffERG demonstrated a picture of RP with cone dysfunction without impacting central or color vision bilaterally. Examined family members were found to be normal. The proband was found to be heterozygous for two novel frameshift pathogenic variants in SCAPER c.3781del, p. (Val1261Serfs*26), c.868_869del, p. (Glu290Serfs*7) both leading to predicted premature termination. The family members tested were found to be heterozygous for SCAPER c.868_869del, p. (Glu290Serfs*7) pathogenic variant confirming their carrier status. CONCLUSION: We report a case of a syndromic RP of previously unreported ocular phenotype associated with SCAPER pathogenic variant, which will add to the phenotypic spectrum of retinopathy and systemic features associated with pathogenic variants in SCAPER.

Pseudoxanthoma elasticum and retinitis pigmentosa in a patient with a novel mutation in the ABCC6 gene.

BACKGROUND: Pseudoxanthoma elasticum (PXE) is an autosomal recessive condition caused by mutations in the ABCC6 gene. Ocular features include angioid streaks, peau d'orange fundus, and drusen. We report a novel ABCC6 mutation causing PXE in a patient with a mixed phenotype of PXE and retinitis pigmentosa (RP). CASE: A 37-year-old female presented with decreased peripheral vision and nyctalopia. Ocular imaging revealed angioid streaks emanating from the optic nerve as well as peripheral pigmentary changes and bone spicules. Genetic testing revealed two mutations in ABCC6 in trans. No other mutation was identified. CONCLUSION: We present a rare case with ocular findings of PXE and RP in a patient with a novel ABCC6 mutation. The patient presented both with peripheral pigmentary changes and angioid streaks. Further investigation into this novel mutation would be beneficial to determine if the mutation is involved in the RP phenotype.

A SYSTEMATIC LITERATURE REVIEW OF DISEASE PROGRESSION REPORTED IN RPGR -ASSOCIATED X-LINKED RETINITIS PIGMENTOSA.

PURPOSE: Retinitis pigmentosa GTPase regulator-associated X-linked retinitis pigmentosa ( RPGR -associated XLRP) is a rare and severe form of retinitis pigmentosa, resulting in progressive visual impairment; however, disease progression data are limited. A systematic literature review was conducted to assess available data on disease progression in RPGR -associated XLRP. METHODS: PubMed, Embase, and select congress abstracts were evaluated through June 2022. Eligible studies included results specific to RPGR -associated XLRP or populations with ≥80% of patients with retinitis pigmentosa carrying disease-causing RPGR variants. End points of interest included visual acuity, visual field, ellipsoid zone width, progression to blindness, and patient-reported outcomes. RESULTS: Fourteen studies met ≥1 end point of interest. Progressive declines in visual acuity, visual field, and ellipsoid zone width were reported across studies. Nearly all publications reported annual declines in visual acuity (3.5%-8.2%). Annual visual field declines ranged from 4.2% to 13.3%. Changes in retinal structure were also observed (ellipsoid zone width changes: -177 to -830 µ m/year). Most studies measured blindness using visual acuity; visual field-based definitions resulted in blindness by age ∼25 years. Patient-reported outcome data were limited. CONCLUSION: Published evidence shows that patients with RPGR -associated XLRP experience progressive decline in visual acuity, visual field, and ellipsoid zone width, eventually resulting in blindness. Additional longitudinal data with standardized end points and expanded collection of patient-reported outcomes are needed to assess visual decline in RPGR -associated XLRP.

PREVALENCE AND CLINICAL FEATURES OF RADIAL FUNDUS AUTOFLUORESCENCE IN HIGH MYOPIC WOMEN.

PURPOSE: To determine the prevalence and characteristics of radial fundus autofluorescence (FAF) in highly myopic women. METHODS: This was a retrospective, observational case study to determine the prevalence of radial FAF in the ultra-widefield FAF images in women. The clinical characteristics of these patients were evaluated. RESULTS: Fifteen of 1,935 (0.78%) highly myopic women were found to have radial FAF. Their mean age was 36.6 ± 25.6 years, and their mean best-corrected visual acuity was 0.3 ± 0.42 logMAR units. The mean axial length (AL) was 28.8 ± 2.8 mm. Among the 15 cases, eight did not have pigmentary changes and seven had pigmentary changes in the ultra-widefield FAF images. The women with the pigmentary changes were significantly older ( P = 0.021), had poorer BCVA ( P = 0.001), and had longer ALs ( P = 0.002). The visual fields and electroretinograms were worse in the eyes with pigmentary changes. CONCLUSION: The prevalence of radial FAF was 0.78% in women with high myopia. These patients might have mutations in the RPGR or RP2 genes and can develop high myopia and retinitis pigmentosa. Ultra-widefield FAF images should be examined in all highly myopic patients for early detection of radial FAF, and myopia prevention and genetic counseling for possible genetic therapy are recommended.

Outcomes of vitreoretinal surgery in eyes with retinitis pigmentosa without retinal detachment.

PURPOSE: Outcomes of retinal detachment (RD) have been discussed in detail in many reports of patients with retinitis pigmentosa (RP). This study tries to understand the outcomes of vitreoretinal (VR) surgery for indications other than RD in the eyes with RP. METHODS: This is a retrospective study that includes clinical data from January 2013 to December 2021. Patients with RP who were treated with a VR surgical intervention were included in the study. The primary outcome of the study was to assess the changes in best-corrected visual acuity. RESULTS: Forty-four eyes of 40 patients with RP were included in the study. Nearly half of the eyes (43%, 19/44) presented from 1 month to 1 year after the onset of diminished vision, with or without floaters. The mean ± standard deviation (SD) best-corrected visual acuity (BCVA) at presentation was 1.30 ± 0.79 logMAR (20/400 ± 20/125). The major surgical indications were vitreous opacities (43.2%, 19/44) and subluxated/dislocated cataractous lenses (25%, 11/44). The median follow-up duration was 8 months (interquartile range (IQR): 1.5-27). Approximately 77% (34/44) of the eyes had improvement in vision. The mean postoperative BCVA at the last follow-up was 0.95 ± 0.73 logMAR (p-value: 0.03). CONCLUSIONS: Most eyes with RP recovered well after VR surgical interventions, with short-term improvements in visual acuity. It may be crucial to address the vitreous opacities and membranes as they hinder the residual central island of vision in RP. However, appropriate counselling is required regarding the progressive nature of retinal neuronal degeneration.