CLINICAL CHARACTERISTICS OF OCCULT MACULAR DYSTROPHY IN FAMILY WITH MUTATION OF RP1L1 GENE

Research progress of RP1L1 gene in disease

Retinitis pigmentosa 1-like 1 (RP1L1) is a component of photoreceptor cilia. Pathogenic variants in RP1L1 cause photoreceptor diseases, suggesting that RP1L1 plays an important role in photoreceptor biology, although its exact function is unknown. To date, RP1L1 variants have been associated with occult macular dystrophy (cone degeneration) and retinitis pigmentosa (rod degeneration). Here, we summarize the reported RP1L1-associated photoreceptor pathogenic mutations. The association between RP1L1 and other diseases (mainly several tumors) is also summarized and RP1L1 is included in a wider range of diseases. Finally, it is necessary to further explore the influence mechanism of RP1L1 gene on the health of photoreceptors and how it participates in the occurrence and development of tumors.

Nationwide epidemiologic survey on incidence of macular dystrophy in Japan

PURPOSE

The aim of this study was to estimate the number of patients in Japan who had visited an ophthalmologist for macular dystrophy of various types, including Best vitelliform macular dystrophy (BVMD), Stargardt disease, occult macular dystrophy (OMD), cone (-rod) dystrophy, X-linked retinoschisis (XLRS), and central areolar choroid dystrophy (CACD).

STUDY DESIGN

Nationwide epidemiologic survey METHODS: Questionnaires were distributed to 965 major facilities, including all the university hospitals in Japan. The aim of the questionnaire was to determine the number of patients with each type of macular dystrophy who had visited an outpatient clinic during the past 5 years (January 2015 to December 2019).

RESULTS

Over 70% of the patients were diagnosed and followed up at university hospitals. The estimated annual number of newly diagnosed cases was as follows: 55.3 for BVMD, 36.7 for Stargardt disease, 35.8 for OMD, 160.6 for cone (-rod) dystrophy, 31.0 for XLRS, 29.8 for CACD, and 174.1 for other types of macular dystrophy. The total number of patients with macular dystrophy diagnosed and followed at major institutions was estimated to be 6651.

CONCLUSION

This was the first nationwide survey of macular dystrophy in Japan and provided an approximate number of affected patients. The diagnosis of macular dystrophy is primarily carried out at facilities with affiliated specialists, such as university hospitals. By examining the incidence of multiple diseases simultaneously, we were able to compare the incidence of each type of macular dystrophy.

Distinct Clinical Effects of Two RP1L1 Hotspots in East Asian Patients With Occult Macular Dystrophy (Miyake Disease): EAOMD Report 4

Purpose

To characterize the clinical effects of two RP1L1 hotspots in patients with East Asian occult macular dystrophy (OMD).

Methods

Fifty-one patients diagnosed with OMD harboring monoallelic pathogenic RP1L1 variants (Miyake disease) from Japan, South Korea, and China were enrolled. Patients were classified into two genotype groups: group A, p.R45W, and group B, missense variants located between amino acids (aa) 1196 and 1201. The clinical parameters of the two genotypes were compared, and deep learning based on spectral-domain optical coherence tomographic (SD-OCT) images was used to distinguish the morphologic differences.

Results

Groups A and B included 29 and 22 patients, respectively. The median age of onset in groups A and B was 14.0 and 40.0 years, respectively. The median logMAR visual acuity of groups A and B was 0.70 and 0.51, respectively, and the survival curve analysis revealed a 15-year difference in vision loss (logMAR 0.22). A statistically significant difference was observed in the visual field classification, but no significant difference was found in the multifocal electroretinographic classification. High accuracy (75.4%) was achieved in classifying genotype groups based on SD-OCT images using machine learning.

Conclusions

Distinct clinical severities and morphologic phenotypes supported by artificial intelligence-based classification were derived from the two investigated RP1L1 hotspots: a more severe phenotype (p.R45W) and a milder phenotype (1196-1201 aa). This newly identified genotype-phenotype association will be valuable for medical care and the design of therapeutic trials.

Occult Macular Dysfunction Syndrome: Identification of Multiple Pathologies in a Clinical Spectrum of Macular Dysfunction with Normal Fundus in East Asian Patients: EAOMD Report No. 5

Occult macular dystrophy (OMD) is the most prevalent form of macular dystrophy in East Asia. Beyond RP1L1, causative genes and mechanisms remain largely uncharacterised. This study aimed to delineate the clinical and genetic characteristics of OMD syndrome (OMDS). Patients clinically diagnosed with OMDS in Japan, South Korea, and China were enrolled. The inclusion criteria were as follows: (1) macular dysfunction and (2) normal fundus appearance. Comprehensive clinical evaluation and genetic assessment were performed to identify the disease-causing variants. Clinical parameters were compared among the genotype groups. Seventy-two patients with OMDS from fifty families were included. The causative genes were RP1L1 in forty-seven patients from thirty families (30/50, 60.0%), CRX in two patients from one family (1/50, 2.0%), GUCY2D in two patients from two families (2/50, 4.0%), and no genes were identified in twenty-one patients from seventeen families (17/50, 34.0%). Different severities were observed in terms of disease onset and the prognosis of visual acuity reduction. This multicentre large cohort study furthers our understanding of the phenotypic and genotypic spectra of patients with macular dystrophy and normal fundus. Evidently, OMDS encompasses multiple Mendelian retinal disorders, each representing unique pathologies that dictate their respective severity and prognostic patterns.

Electrophysiological Evaluation of Macular Dystrophies

Macular dystrophies are a heterogeneous group of genetic disorders that often severely threatens the bilateral central vision of the affected patient. While advances in molecular genetics have been instrumental in the understanding and diagnosis of these disorders, there remains significant phenotypical variation among patients within any particular subset of macular dystrophies. Electrophysiological testing remains a vital tool not only to characterize vision loss for differential diagnosis but also to understand the pathophysiology of these disorders and to monitor the treatment effect, potentially leading to therapeutic advances. This review summarizes the application of electrophysiological testing in macular dystrophies, including Stargardt disease, bestrophinopathies, X-linked retinoschisis, Sorsby fundus dystrophy, Doyne honeycomb retina dystrophy, autosomal dominant drusen, occult macular dystrophy, North Carolina macular dystrophy, pattern dystrophy, and central areolar choroidal dystrophy.

Occult Macular Dystrophy: a case report and major review

BACKGROUND

Occult Macular Dystrophy (OMD), a rare autosomal dominant disorder caused by mutations in the retinitis pigmentosa 1-like protein 1 gene (RP1L1), is characterized by loss of central visual acuity in the absence of fundoscopic abnormalities. In patients suspected of having OMD based on unexplained central vision loss and/or photophobia, changes may be detected with spectral-domain optical coherence tomography. Subsequently, the diagnosis can be confirmed with genetic analysis.We report a case of an 18-year-old White male whose suspected diagnosis of OMD was confirmed by molecular testing. We conducted an extensive review of the literature of previously reported patients with OMD to date.

METHODS

A PubMed search of "RP1L1 and Occult Macular Dystrophy" revealed 34 papers. There were 225 individuals with genetically confirmed, symptomatic OMD; an additional 15 had a confirmed mutation but were asymptomatic and discovered incidentally.

RESULTS

Our patient presented with a 10-year history of unexplained loss of central visual acuity and photophobia. Genetic analysis confirmed the presence of a p.R45W substitution on the RP1L1 gene, the most common pathologic mutation in OMD.

CONCLUSIONS

Due to the lack of appreciable fundoscopic changes, correct identification of the disease can be difficult. Incomplete penetrance has been associated with the condition, and the age of onset is highly variable. Much of the research discussing OMD has come from Eastern Asia, but whether this is due to a heightened awareness and screening protocols, or increased incidence is unclear. Additional research and increased awareness globally will help with more timely and accurate diagnoses.

Multimodal imaging evaluation of occult macular dystrophy associated with a novel RP1L1 variant

Purpose

Occult Macular Dystrophy (OMD) is an autosomal dominant inherited retinal dystrophy caused by mutations in the retinitis pigmentosa 1-like 1 (RP1L1) gene. The present study describes a novel RP1L1 variant, identified for the first time in two Italian sisters diagnosed with OMD, along with multimodal imaging features, including Optical Coherence Tomography (OCT) Angiography.

Methods

We performed multimodal imaging including spectral-domain OCT, blue light autofluorescence (BAF), infrared autofluorescence (IRAF), swept-source OCT Angiography (OCTA), full-field and multifocal electroretinography. Genetic analysis was performed using Next-Generation Sequencing. Pathogenic potential of nonsynonymous novel variants was scored with two in silico algorithms.

Results

Proband 1 (P1) and proband 2 (P2) were two Italian sisters of 61 and 56 years old. Both reported a history of progressive visual loss without fundoscopic alterations. P1 reported a 4-year history of rapid visual function worsening, and her best-corrected visual acuity (BCVA) was counting fingers in both eyes. P2 reported a 20-year history of mild but progressive visual acuity loss, and her BCVA was 1/10 and 2/10 respectively in her right and left eye. Structural OCT displayed disorganization of outer retinal bands at the macula and foveal cavitation; loss of foveal photoreceptors was remarkably evident on en-face OCT slabs. OCTA quantitative analysis found that vessel density was reduced both at SCP and DCP while choriocapillaris blood flow was relatively spared. Genetic analysis found the same rare dominant c.2873G > C, p.Arg958Pro variant in the RP1L1 gene. The substitution was regarded as moderately radical according to Grantham score while PolyPhen2 classified the amino acidic substitution as probably damaging.

Conclusions and importance

Our study expands the mutational spectrum of RP1L1 gene: the rare c.2873G > C, p.Arg958Pro missense variant may be considered a new pathogenic variant for OMD, the first to be identified exclusively in an Italian family. Moreover, our quantitative OCTA data suggest that OMD is characterized by a rarefaction of superficial and deep capillary plexus.

Visual Field Characteristics in East Asian Patients With Occult Macular Dystrophy (Miyake Disease): EAOMD Report No. 3

Purpose

The purpose of this study was to investigate the perimetric features and their associations with structural and functional features in patients with RP1L1-associated occult macular dystrophy (OMD; i.e. Miyake disease).

Methods

In this international, multicenter, retrospective cohort study, 76 eyes of 38 patients from an East Asian cohort of patients with RP1L1-associated OMD were recruited. Visual field tests were performed using standard automated perimetry, and the patients were classified into three perimetric groups based on the visual field findings: central scotoma, other scotoma (e.g. paracentral scotoma), and no scotoma. The association of the structural and functional findings with the perimetric findings was evaluated.

Results

Fifty-four eyes (71.1%) showed central scotoma, 14 (18.4%) had other scotomata, and 8 (10.5%) had no scotoma. Central scotoma was mostly noted in both eyes (96.3%) and within the central 10 degrees (90.7%). Among the three perimetric groups, there were significant differences in visual symptoms, best-corrected visual acuity (BCVA), and structural phenotypes (i.e. severity of photoreceptor changes). The central scotoma group showed worse BCVA often with severe structural abnormalities (96.3%) and a pathogenic variant of p.R45W (72.2%). The multifocal electroretinogram (mfERG) groups largely corresponded with the perimetric groups; however, 8 (10.5%) of 76 eyes showed mfERG abnormalities preceding typical central scotoma.

Conclusions

The patterns of scotoma with different clinical severity were first identified in occult macular dystrophy, and central scotoma, a severe pattern, was most frequently observed. These perimetric patterns were associated with the severity of BCVA, structural phenotypes, genotype, and objective functional characteristics which may precede in some cases.

An extended phenotype of RP1L1 maculopathy - case report

BACKGROUND

To report the ophthalmological findings of a new phenotypical variant of RP1L1 maculopathy in an Indian patient with a homozygous variant in the RP1L1 gene.

MATERIALS AND METHODS

A 39-year-old male presented with complaints of disturbance in the central field of vision in both eyes (BE) for a duration of 6 months. He underwent ophthalmic examinations and diagnostic imaging. A complete retinal degeneration panel consisting of 228 genes was evaluated for pathologic variations using next-generation sequencing (NGS), which showed a variant in the RP1L1 gene.

RESULTS

On fundus examination, he was found to have ill-defined foveal mottling in BE. Spectral domain optical coherence tomography (SD-OCT) showed sub-foveal hyper-reflective deposits and outer retinal layer disruption. A provisional diagnosis of the atypical variant of adult-onset foveomacular vitelliform dystrophy (AOFVD) was made on the basis of clinical, OCT, Fundus autofluorescence (FAF) and electrophysiological features. Genetic assessment of the proband revealed the presence of a homozygous base pair deletion in exon 4 of RP1L1 gene (chr8:g.10468194_10468195del), which results in frameshift and premature truncation of the protein 24 amino acids downstream to codon 1138 (p.Lys1138SerfsTer24). This variant was confirmed in the proband's parents by Sanger sequencing. The diagnosis was revised to RP1L1 maculopathy, as the RP1L1 gene variant is most commonly associated with this entity.

CONCLUSION

This report presents the multimodal imaging of a previously unreported phenotype of RP1L1 maculopathy associated with a genetic variant of RP1L1 gene, thereby expanding the spectrum associated with RP1L1 maculopathy.

RP1L1 rs3924612 gene polymorphism and RP1L1 protein associations among patients with early age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is one of the most common causes of blindness in developed world countries. It mainly affects the elderly. The incidence of the disease is only slightly below that of cancer and cardiovascular diseases. This study aimed to determine the association of RP1L1 single nucleotide polymorphism and serum RP1L1 levels with the onset of the early AMD.

AIM

The aim of this study was to determine the association of RP1L1 single nucleotide polymorphism with the onset of the early age-related macular degeneration (AMD).

METHODS

The study examined 615 subjects: 309 with a diagnosis of the early AMD and 306 healthy controls. Samples of DNA from peripheral blood leukocytes were extracted by the DNA salting-out method. Genotyping was carried out by the real-time polymerase chain reaction. Serum levels of RP1L1 protein were evaluated using an ELISA kit. The results were assessed using the statistical analysis method of "IBM SPSS Statistics 23.0".

RESULTS

We have found that the RP1L1 rs3924612 C/G genotype increases the odds of the early AMD development in females (p <.05/2). Also, we found that RP1L1 rs3924612 C/G and G/G genotypes increase the odds of the early AMD in the age group of 56-68 years (p < .05/2). Serum RP1L1 levels were evaluated in study groups but no statistically significant associations were found.

CONCLUSION

Based on these results we concluded that RP1L1 rs3924612 polymorphism was associated with the early AMD development, but not with the RP1L1 level changes.

Spatial Functional Characteristics of East Asian Patients With Occult Macular Dystrophy (Miyake Disease); EAOMD Report No. 2

PURPOSE

To describe the functional phenotypic features of East Asian patients with RP1L1-associated occult macular dystrophy (ie, Miyake disease).

DESIGN

An international multicenter retrospective cohort study.

METHODS

Twenty-eight participants (53 eyes) with Miyake disease were enrolled at 3 centers (in Japan, China, and South Korea). Ophthalmologic examinations including spectral-domain optical coherence tomography (SDOCT) and multifocal electroretinogram (mfERG) were performed. Patients were classified into 3 functional groups based on mfERG: Group 1, paracentral dysfunction with relatively preserved central/peripheral function; Group 2, homogeneous central dysfunction with preserved peripheral function; and Group 3, widespread dysfunction over the recorded area. Three functional phenotypes were compared in clinical parameters and SDOCT morphologic classification (severe phenotype, blurred/flat ellipsoid zone and absence of the interdigitation zone; mild phenotype, preserved ellipsoid zone).

RESULTS

There were 8 eyes in Group 1, 40 eyes in Group 2, and 5 eyes in Group 3. The patients in Group 1 showed significantly later onset (P = .005) and shorter disease duration (P = .002), compared with those in Group 2. All 8 eyes in Group 1 showed the mild morphologic phenotype, while 43 of 45 eyes in Groups 2 and 3 presented the severe phenotype, which identified a significant association between the functional grouping and the morphologic classification (P < .001).

CONCLUSIONS

A spectrum of functional phenotypes of Miyake disease was first documented with identification of 3 functional subtypes. Patients with paracentral dysfunction had the mildest phenotype, and those with homogeneous central or widespread dysfunction showed overlapping clinical findings with severe photoreceptor changes, suggesting various extents of visual impairment.

A variant in the RP1L1 gene in a family with occult macular dystrophy in a predicted intrinsically disordered region

SIGNIFICANCE

The responsible genetic variants for occult macular dystrophy (OMD) were found at the predicted intrinsically disordered region (IDR) of the RP1L1 gene.

PURPOSE

We examined the phenotypes and genotypes of family members from OMD. In addition, the genetic characteristics of the RP1L1 gene in OMD were investigated.

METHODS

Whole-exome sequencing was applied on two affected family members, and Sanger sequencing was performed on three members. The structural property of RP1L1 and pathogenic variants was analyzed using predictor of natural disordered regions (PONDR).

RESULTS

Two affected members showed moderate visual impairment and relative central scotoma. The spectral domain optical coherence tomography (SD-OCT) images showed an absence of the interdigitation zone (IZ) and ellipsoid zone (EZ) in one case, and an obscure EZ line in the other case. A RP1L1 variant (c.3593 C > T, p.Ser1198Phe) was identified in two affected members but not in the unaffected member. The PONDR analysis showed that the region from p.1189 to p.1248 could be predicted to be an IDR in the RP1L1 molecule. And the p. Ser1198Phe variant showed significant reduction of PONDR score.

CONCLUSIONS

Although, the major pathogenic variant of OMD is p.Arg45Trp, multiple reports indicate that the region between p.1194 and p.1201 is another hot spot of OMD. The PONDR analysis predicted that the RP1L1 molecule is one of the intrinsically disordered proteins. It is speculated that the region around p.1200 is essential for the normal function of the RP1L1 molecule, and the missense variants of that area cause the development of OMD.

Progress of macular atrophy during 30 months' follow-up in a patient with spinocerebellar ataxia type1 (SCA1)

PURPOSE

To report the 30-months' course of macular dystrophy in a patient with genetically confirmed spinocerebellar ataxia type1 (SCA1).

METHODS

Detailed ophthalmological examinations including best-corrected visual acuity (BCVA), perimetry, multimodal fundus imaging, and electrophysiological recordings were performed on a 52-year-old woman with SCA1. The number of CAG sequence repeats of the candidate gene was verified.

RESULTS

The baseline decimal BCVA was 0.2 OD and 0.3 OS. Goldman perimetry showed relative central scotomas and slight enlargements of Mariotte blind spot bilaterally. Ophthalmoscopy revealed no abnormalities in the macula and optic disk. Fundus autofluorescence (FAF) showed a circular hyperautofluorescence and round-shaped hypoautofluorescence in the macula. Optical coherence tomography (OCT) showed a loss of the interdigitation zone and ellipsoid zone (EZ) in the macula. Full-field scotopic and photopic Full-field electroretinograms (ERGs) were normal, and multifocal ERGs were decreased in the central area. After 30 months, the BCVA had not changed, but the FAF showed a spark-like hypoautofluorescence in the macula. The abnormal area of the EZ had expanded toward the periphery, and the rate of EZ loss was 199.7%/year OD and 206.8%/year OS. Genetic examinations revealed an increase in the number of heterozygous CAG repeats in the ATXN1 gene, and the CAG repeat number of the mutant allele ranged from 43 to 48.

CONCLUSIONS

The full-field scotopic and photopic ERGs were normal. The mfERGs were significantly smaller in the central region. OCT demonstrated bilateral photoreceptor atrophy in the macula, and the rate of EZ loss was more rapid than in other macular dystrophies. Spark-like hypoautofluorescence appeared during the course of the disease process which might be a specific feature of SCA1-related retinopathy.

RP1L1 and inherited photoreceptor disease: A review

Retinitis pigmentosa 1-like 1 (RP1L1) is a component of the photoreceptor cilium. Pathogenic variants in RP1L1 lead to photoreceptor disease, suggesting an important role for RP1L1 in photoreceptor biology, though its exact function is unknown. To date, RP1L1 variants have been associated with occult macular dystrophy (a cone degeneration) and retinitis pigmentosa (a rod disease). Here, we summarize reported RP1L1-associated photoreceptor conditions and disease-causing RP1L1 variants. We also discuss novel associations between RP1L1 and additional photoreceptor conditions-besides occult macular dystrophy and retinitis pigmentosa-and fit RP1L1 into the broader scope of photoreceptor disease. RP1L1 appears to have a complex relationship with other photoreceptor proteins and may modify disease phenotype. Ultimately, further exploration of the relationship between RP1L1, other cilium components, and their impact on photoreceptor health is needed.

Clinical Stages of Occult Macular Dystrophy Based on Optical Coherence Tomographic Findings

Purpose

To determine the course of occult macular dystrophy (OMD, Miyake's disease) and to propose stages of OMD based on the optical coherence tomographic (OCT) findings.

Methods

Sixty-one patients from 33 families with OMD who carried one of the proven variants of the RP1L1 gene were studied at seven centers in Japan. Ophthalmological examinations including the best-corrected visual acuity (BVCA) and OCT were performed.

Results

The median age at the last visit was 50 years with a range of 10 to 88 years, and the median age at the symptom onset was 30 years with a range of 3 to 60 years. There were significant negative correlations between the duration of OMD and BCVA, the central retinal thickness (CRT) and the thickness between external limiting membrane and retinal pigment epithelium (ERT). The BCVA gradually decreased for 10 years after symptom onset and was stable thereafter. Kaplan-Meier survival curves of the BCVA and retinal thickness showed that all of the patients had retained a vision of 1.0 logMAR, and over 80% of the patients had retained 50% thickness of the normal CRT and ERT for at least 60 years after symptom onset. The stages of OMD based on the visual symptoms and OCT findings are proposed.

Conclusions

The photoreceptors do not become completely atrophic even at the late stage, which may account for the good retinal pigment epithelium (RPE) structure and normal-appearing fundus. The proposed stages facilitate the investigation of the pathogenicity of OMD and provide information to determine the effectiveness of therapeutic procedures.

Phenotypical Characteristics of POC1B-Associated Retinopathy in Japanese Cohort: Cone Dystrophy With Normal Funduscopic Appearance

Purpose

Cone/cone-rod dystrophy is a large group of retinal disorders with both phonotypic and genetic heterogeneity. The purpose of this study was to characterize the phenotype of eight patients from seven families harboring POC1B mutations in a cohort of the Japan Eye Genetics Consortium (JEGC).

Methods

Whole-exome sequencing with targeted analyses identified homozygous or compound heterozygous mutations of the POC1B gene in 7 of 548 families in the JEGC database. Ophthalmologic examinations including the best-corrected visual acuity, perimetry, fundus photography, fundus autofluorescence imaging, optical coherence tomography, and full-field and multifocal electroretinography (ERGs) were performed.

Results

There were four men and four women whose median age at the onset of symptoms was 15.6 years (range, 6-23 years) and that at the time of examination was 40.3 years (range, 22-67 years). The best-corrected visual acuity ranged from -0.08 to 1.52 logMAR units. The funduscopic appearance was normal in all the cases except in one case with faint mottling in the fovea. Optical coherence tomography revealed an absence of the interdigitation zone and blurred ellipsoid zone in the posterior pole, but the foveal structures were preserved in three cases. The full-field photopic ERGs were reduced or extinguished with normal scotopic responses. The central responses of the multifocal ERGs were preserved in two cases. The diagnosis was either generalized cone dystrophy in five cases or cone dystrophy with foveal sparing in three cases.

Conclusions

Generalized or peripheral cone dystrophy with normal funduscopic appearance is the representative phenotype of POC1B-associated retinopathy in our cohort.

Novel homozygous loss-of-function mutations in RP1 and RP1L1 genes in retinitis pigmentosa patients

Background: Retinitis pigmentosa (RP) is a heterogeneous group of ocular dystrophy. It is challenging to identify the underlying genetic defect in individuals with RP due to huge genetic heterogeneity. This study was designed to delineate the genetic defect(s) underlying RP in extended Saudi families and to describe the possible disease mechanism.Materials and Methods: Fundus photography and a high definition optical coherence tomography (HD-OCT) were performed in order to detect the earlier stages of macular degeneration. Genomic DNA was extracted followed by genome-wide SNP genotyping and whole exome sequencing (WES). Exome data was filtered to identify the genetic variant(s) of interest.Results: Clinical examination showed that affected individuals manifest key features of RP. The fundus exam shows pale optic disc and bone spicules at the periphery. OCT shows macular degeneration as early as at the age of 4 years. Whole genome scan by SNPs identified multiple homozygous regions. WES identified a 10 bps novel insertion mutation (c.3544_3545insAGAAAAGCTG; p.Ala1182fs) in the RP1 gene in both affected individuals of family A. Affected individual from family B showed a large insertion of 48 nucleotides in the coding part of the RP1L1 gene (c.3955_3956insGGACTAAAGTAATAGAAGGGCTGCAAGAAGAGAGGGTGCAGTTAGAGG; p.Ala1319fs). Sanger sequencing validates the autosomal recessive inheritance of the mutations.Conclusion: The results strongly suggest that the insertion mutations in the RP1 and RP1L1 genes are responsible for the retinal phenotype in affected individuals from two families. Heterozygous individuals are asymptomatic carriers. We propose that the protective allele in other homozygous regions in heterozygous carriers contribute to the phenotypic variability in asymptomatic individuals.

Whole-exome sequencing identifies novel mutations in genes responsible for retinitis pigmentosa in 2 nonconsanguineous Chinese families

AIM

To detect the pathogenetic mutations responsible for nonsyndromic autosomal recessive retinitis pigmentosa (RP) in 2 nonconsanguineous Chinese families.

METHODS

The clinical data, including detailed medical history, best corrected visual acuity (BCVA), slit-lamp biomicroscope examination, fundus photography, optical coherence tomography, static perimetry, and full field electroretinogram, were collected from the members of 2 nonconsanguineous Chinese families preliminarily diagnosed with RP. Genomic DNA was extracted from the probands and other available family members; whole-exome sequencing was conducted with the DNA samples provided by the probands, and all mutations detected by whole-exome sequencing were verified using Sanger sequencing in the probands and the other available family members. The verified novel mutations were further sequenced in 192 ethnicity matched healthy controls.

RESULTS

The patients from the 2 families exhibited the typical symptoms of RP, including night blindness and progressive constriction of the visual field, and the fundus examinations showed attenuated retinal arterioles, peripheral bone spicule pigment deposits, and waxy optic discs. Whole-exome sequencing revealed a novel nonsense mutation in FAM161A (c.943A>T, p.Lys315*) and compound heterozygous mutations in RP1L1 (c.56C>A, p.Pro19His; c.5470C>T, p.Gln1824*). The nonsense c.5470C>T, p.Gln1824* mutation was novel. All mutations were verified by Sanger sequencing. The mutation p.Lys315* in FAM161A co-segregated with the phenotype, and all the nonsense mutations were absent from the ethnicity matched healthy controls and all available databases.

CONCLUSION

We identify 2 novel mutations in genes responsible for autosomal recessive RP, and the mutation in FAM161A is reported for the first time in a Chinese population. Our result not only enriches the knowledge of the mutation frequency and spectrum in the genes responsible for nonsyndromic RP but also provides a new target for future gene therapy.

Clinical and Genetic Characteristics of East Asian Patients with Occult Macular Dystrophy (Miyake Disease): East Asia Occult Macular Dystrophy Studies Report Number 1

PURPOSE

To describe the clinical and genetic characteristics of the cohort enrolled in the East Asian studies of occult macular dystrophy (OMD).

DESIGN

International, multicenter, retrospective cohort studies.

PARTICIPANTS

A total of 36 participants from 21 families with a clinical diagnosis of OMD and harboring pathogenic RP1L1 variants (i.e., Miyake disease) were enrolled from 3 centers in Japan, China, and South Korea.

METHODS

A detailed history was obtained, and comprehensive ophthalmological examinations including spectral-domain OCT were performed. All detected sequence variants in the RP1L1 gene were reviewed, and in silico analysis was performed, including allele frequency analyses and pathogenicity predictions.

MAIN OUTCOME MEASURES

Onset of disease, visual acuity (VA) converted to the logarithm of the minimum angle of resolution (logMAR), OCT findings, and effect of detected variants.

RESULTS

Eleven families from Japan, 6 from South Korea, and 4 from China were recruited. There were 12 female and 24 male participants. The median age of onset was 25.5 years (range, 2-73), and the median age at the latest examination was 46.0 years (range, 11-86). The median VA (logMAR) was 0.65 (range, -0.08-1.22) in the right eye and 0.65 (-0.08-1.10) in the left eye. A significant correlation between onset of disease and VA was revealed. The Classical morphologic phenotype showing both blurred ellipsoid zone and absence of interdigitation zone of the photoreceptors was demonstrated in 30 patients (83.3%), and subtle photoreceptor architectural changes were demonstrated in 6 patients (16.6%). Eight pathogenic RP1L1 variants were identified, including 6 reported variants and 1 novel variant: p.R45W, p.T1194M/p.T1196I (complex), p.S1199C, p.G1200A, p.G1200D, p.V1201G, and p.S1198F, respectively. Two variants were recurrent: p.R45W (11 families, 52.4%) and p.S1199C (5 families, 23.8%). The pathogenic missense variants in 10 families (47.6%) were located within the previously reported unique motif, including 6 amino acids (1196-1201).

CONCLUSIONS

There is a large spectrum of clinical findings in Miyake disease, including various onset of disease and VA, whereas the characteristic photoreceptor microstructures were shared in most cases. Two hot spots including amino acid numbers 45 and 1196-1201 in the RP1L1 gene were confirmed in the East Asian population.

New clinical ultrahigh-resolution SD-OCT using A-scan matching algorithm

PURPOSE

A new clinical ultrahigh-resolution spectral domain optical coherence tomography (UHR-SD-OCT) system using an original averaging technique named "A-scan matching algorithm" was developed. The aim of this study was to determine whether our new UHR-SD-OCT system can obtain clearer sectional images of the retina than conventional standard resolution SD-OCT systems (SR-SD-OCT).

METHODS

We recorded horizontal B-scan images of 42 normal eyes using our new UHR-SD-OCT device (Bi-μ, Kowa) and a conventional SR-SD-OCT (Spectralis, Heidelberg). To evaluate the clarity of the interdigitation zone (IZ) subjectively, the integrity of IZ was divided into three types by two raters. To evaluate the clarity of the IZ objectively, a peak height score (PHS) was calculated at five different points of the macula using the longitudinal reflectivity profile.

RESULTS

The mean (± SD) of the subjective visibility score of the IZ in the UHR-SD-OCT images was 2.64 ± 0.54 which was significantly higher than the 2.46 ± 0.46 in the SR-SD-OCT images (P = 0.02). The PHS was also significantly higher for the UHR-SD-OCT than for the SR-SD-OCT images at all five locations (all P < 0.01).

CONCLUSION

The results indicate that the newly developed clinical UHR-SD-OCT instrument using the A-scan matching algorithm can obtain clearer images of the IZ, and they suggest that this device should be clinically useful in detecting finer structural abnormalities of the outer retina.

Next-Generation Sequencing-Aided Rapid Molecular Diagnosis of Occult Macular Dystrophy in a Chinese Family

Purpose: To show early, rapid and accurate molecular diagnosis of occult macular dystrophy (OMD) in a four-generation Chinese family with inherited macular dystrophy.

Methods: In the current study, we comprehensively screened 130 genes involved in common inherited non-syndromic eye diseases with next-generation sequencing-based target capture sequencing of the proband of a four-generation Chinese family that has suffered from maculopathy without a definitive diagnosis for over 10 years. Variants were filtered and analyzed to identify possible disease-causing variants before validation by Sanger sequencing.

Results: Two heterozygous mutations—RP1L1 c.133 C > T (p.Arg45Trp), which is a hot spot for OMD, and ABCA4 c.6119 G > A (p.Arg2040Gln), which was identified in Stargardt’s disease were found in three patients, but neither of the mutations was found in the unaffected individuals in the same family, who are phenotypically normal or in the normal control volunteers.

Conclusion: These results cannot only confirm the diagnosis of OMD in the proband, but also provide presymptomatic diagnosis of the proband’s children before the onset of visual acuity impairment and guidance regarding the prognosis and management of these patients. Heterozygous mutations of RP1L1 c.133 C > T (p.Arg45Trp) and ABCA4 c.6119 G > A (p.Arg2040Gln) are likely responsible for OMD. Our results further extend our current understanding of the genetic basis of OMD, and emphasize the importance of molecular diagnosis and genetic counseling for OMD.

ERG and OCT findings of a patient with a clinical diagnosis of occult macular dystrophy in a patient of Ashkenazi Jewish descent associated with a novel mutation in the gene encoding RP1L1

A 57-year-old man with a past medical history of diabetes presented for consultation with a several year history of slowly progressive vision loss in both eyes, which continued to deteriorate over 7 years of follow-up. Multimodal imaging was performed and was significant for the following: on spectral domain optical coherence tomography, a gap lesion was present in the ellipsoid layer, beneath the umbo, as well as subtle macular changes on auto fluorescence imaging. Multifocal electroretinography was performed and was abnormal, and a clinical diagnosis of occult macular dystrophy was made. The patient was subsequently evaluated with genetic testing that revealed a novel p.P73S:c 217C>T nonsense mutation within the retinitis pigmentosa 1-like-1 (RP1L1) gene. The clinical significance of the identified variation will require further investigation.

Successful scleral buckling of late-onset visual decrease in eye with retinal folds

PURPOSE

To describe the outcome of scleral buckling to treat radial retinal folds (RFs) that caused a late-onset and sudden visual decrease with impairment of the fovea.

METHODS

This is an observational case report. Ophthalmic examinations were performed preoperatively and postoperatively and included measurement of the best-corrected visual acuity (BCVA), fundus examination, fluorescein angiography, focal macular electroretinography (FM-ERG), and spectral-domain optical coherence tomography (OCT).

RESULTS

A patient, whose case was reported previously, had a superonasal retinal detachment with a dislocated fovea and good BCVA in her right eye and a sustained BCVA of 40/50 by age 17 years and 3 months. The BCVA decreased suddenly to 20/200 at age 17 years and 11 months. Fundus examinations showed micro-dislocation of the fovea to the RFs and narrowing of the RFs compared with the previous report. FM-ERG showed an almost extinguished response, and OCT images showed abnormalities of the outer nuclear and photoreceptor layers. Encircling and radial scleral buckling was performed. Four months postoperatively, the BCVA improved to 30/50, which corresponded to the recovery of the FM-ERG response and findings on the OCT images. One year and 3 months postoperatively, the BCVA recovered to 35/50 with repositioning of the fovea.

CONCLUSIONS

Simultaneous encircling and radial scleral buckling resulted in the recovery of both retinal function and structure in the current case and is a useful surgical option to treat late-onset progressive RFs due to intensification of traction.

Multimodal Approach to Monitoring and Investigating Cone Structure and Function in an Inherited Macular Dystrophy

PURPOSE

To examine a female subject, her father, and a brother harboring a missense mutation of the retinitis pigmentosa 1-like 1 (RP1L1) gene, over 2 years of follow-up.

DESIGN

Observational case series.

METHODS

setting: Fondazione G.B. Bietti IRCCS, Rome, Italy.

STUDY POPULATION

RP1L1 family members and controls.

MAIN OUTCOME MEASURES

Images of the cone mosaic acquired with an adaptive optics retinal camera, spectral-domain optical coherence tomography (SD OCT), and full-field and multifocal electroretinography (mfERG).

RESULTS

In the proband, best-corrected visual acuity (≤0.7 logMAR) was stable in both eyes during follow-up, though analysis of adaptive optics images showed decreased cone density in the central 9 degrees from the fovea with respect to controls (P < .05) and cone density loss in the parafoveal area (2 degrees; <12%-16%) during follow-up. Texture analysis of SD OCT images identified abnormalities of the ellipsoid zone in the central 7 degrees, while mfERG response amplitudes were reduced only in the central 5 degrees relative to controls. In the proband's father, who had 0.0 logMAR visual acuity, significant cone loss was found in the central 7 degrees from the fovea (P < .05); abnormal SD OCT and mfERG values with respect to controls were found in corresponding retinal areas. No defects in the cone structure and function were found in the proband's brother, who had 0.0 logMAR visual acuity.

CONCLUSIONS

Occult macular dystrophy was diagnosed based on genetic and multimodal ophthalmic findings. The quantitative assessment of photoreceptor survival or loss, based on analysis of adaptive optics retinal images, was valuable to monitor disease progression at a cellular level.

Occult macular dystrophy

Occult macular dystrophy (OMD) was first reported in 1989 as a hereditary macular disease without visible fundus abnormalities. Patients with OMD are characterized by a progressive decrease of visual acuity but have normal fundus and fluorescein angiograms with both the rod and cone components of the full-field electroretinograms (ERGs) essentially normal. However, the focal macular ERGs and multifocal ERGs are severely attenuated. These findings indicate that the retinal dysfunction is confined to the macula. Optical coherence tomography (OCT) has shown structural changes in the outer nuclear and/or photoreceptor layers. Genetic analyses of OMD pedigrees have identified dominant mutations in the RP1L1 gene. However, the same mutations were not detected in sporadic cases, suggesting that several independent mutations can lead to the OMD phenotype. The purpose of this paper is to review the history of OMD, the visual functions determined psychophysically, ERG findings, OCT characteristics and genetic findings in patients with OMD.

Cone dystrophy in patient with homozygous RP1L1 mutation

The purpose of this study was to determine whether an autosomal recessive cone dystrophy was caused by a homozygous RP1L1 mutation. A family including one subject affected with cone dystrophy and four unaffected members without evidence of consanguinity underwent detailed ophthalmic evaluations. The ellipsoid and interdigitation zones on the spectral-domain optical coherence tomography images were disorganized in the proband. The proband had a reduced amplitude of cone and flicker full-field electroretinograms (ERGs). Focal macular ERGs and multifocal ERGs were severely reduced in the proband. A homozygous RP1L1 mutation (c.3628T>C, p.S1210P) was identified in the proband. Family members who were heterozygous for the p.S1210P mutation had normal visual acuity and normal results of clinical evaluations. To investigate other putative pathogenic variant(s), a next-generation sequencing (NGS) approach was applied to the proband. NGS identified missense changes in the heterozygous state of the PCDH15, RPGRIP1, and GPR98 genes. None of these variants cosegregated with the phenotype and were predicted to be benign reinforcing the putative pathogenicity of the RP1L1 homozygous mutation. The AO images showed a severe reduction of the cone density in the proband. Our findings indicate that a homozygous p.S1210P exchange in the RP1L1 gene can cause cone dystrophy.

Changes in outer retinal microstructures during six month period in eyes with acute zonal occult outer retinopathy-complex

Purpose

To study the changes in the outer retinal microstructures during a six month period after the onset of acute zonal occult outer retinopathy (AZOOR)-complex by spectral-domain optical coherence tomography (SD-OCT).

Methods

Seventeen eyes of 17 patients with the AZOOR-complex were studied. The integrity of the external limiting membrane (ELM), ellipsoid zone (EZ; also called the inner/outer segment junction), and interdigitation zone (IDZ; also called the cone outer segment tips) were evaluated in the SD-OCT images obtained at the initial visit and at six months. The three highly reflective bands were divided into three types; continuous, discontinuous, and absent. The integrity of the outer nuclear layer (ONL) was also assessed.

Results

Among the three highly reflective bands, the IDZ was most altered at the initial visit and least recovered at six months. Fifteen of 17 eyes (88%) had a recovery of at least one of the three bands at six months in the retinal area where the ONL was intact, and these areas showed an improvement of visual field. Three eyes (18%) had retinal areas where the ONL was absent at the initial visit, and there was no recovery in both the retinal structures and visual fields in these areas.

Conclusions

Our results indicate that more than 85% eyes with AZOOR-complex show some recovery in the microstructures of the outer retina during a six month period if the ONL is intact. We conclude that SD-OCT is a useful method to monitor the changes of the outer retinal microstructure in eyes with the AZOOR-complex.

Two siblings with late-onset cone-rod dystrophy and no visible macular degeneration

Background

We report our findings in two siblings with late-onset cone–rod dystrophy (CRD) with no visible macular degeneration.

Cases and methods

Case 1 was an 82-year-old man who first noticed a decrease in vision and color blindness in his early seventies. His mother and younger sister also had visual disturbances. His decimal visual acuity was 0.3 in the right eye and 0.2 in the left eye. Ophthalmoscopy showed normal fundi, and fluorescein angiography was also normal in both eyes. The photopic single flash and flicker eletroretinograms (ERGs) were severely attenuated and the scotopic ERGs were slightly reduced in both eyes. Case 2 was the 80-year-old younger sister of Case 1. She first noticed a decline in vision and photophobia in both eyes in her early seventies. Her decimal visual acuity was 0.4 in the right eye and 0.2 in the left eye. Ophthalmoscopy showed mottling of the retinal pigment epithelium in the midperiphery with no visible macular degeneration. The photopic single flash and flicker ERGs were severely attenuated, and the scotopic ERGs were slightly reduced in both eyes.

Conclusion

These siblings are the oldest reported cases of CRD with no visible macular degeneration. Thus, CRD should be considered in patients with reduced visual acuity, color blindness, and photophobia even if they are older than 70 years.