Radial fundus autofluorescence in the periphery in patients with X-linked retinitis pigmentosa

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.

Genetic spectrum, retinal phenotype, and peripapillary RNFL thickness in RPGR heterozygotes

PURPOSE

Phenotypic heterogeneity with variable severity has been reported in female carriers of retinitis pigmentosa GTPase regulator (RPGR) mutations, including a male-type phenotype. A phenomenon not fully understood is peripapillary retinal nerve fiber layer (pRNFL) thickening in male patients with RPGR-associated X-linked retinitis pigmentosa, especially in the temporal sector. We aim to describe the genetic spectrum, retinal phenotypes, and pRNFL thickness in a cohort of Caucasian RPGR-mutation heterozygotes.

METHODS

A cross-sectional study was conducted at an inherited retinal degeneration (IRD) reference center in Portugal. Female patients heterozygous for clinically significant RPGR variants were identified using the IRD-PT registry. A complete ophthalmologic examination was performed, complemented by macular and peripapillary spectral domain optical coherence tomography (SD-OCT), ultra-widefield color fundus photography (UW-CFP), and ultra-widefield fundus autofluorescence (UW-FAF). The retinal phenotypes were graded according to previously described classifications. The pRNFL thickness across the superior, inferior, nasal, and temporal quadrants was compared to the Spectralis® RNFL age-adjusted reference database.

RESULTS

Forty-eight eyes from 24 females (10 families) were included in the study. Genetic analysis yielded 8 distinct clinically significant frameshift variants in RPGR gene, 3 of which herein reported for the first time. No association was found between mutation location and best-corrected visual acuity (BCVA) or retinal phenotype. Age was associated with worse BCVA and more advanced phenotypes on SD-OCT, UW-CFP, and UW-FAF. Seven women (29.17%) presented a male-type phenotype on UW-FAF in at least one eye. An association was found between UW-FAF and pRNFL thickness in the temporal sector (p = 0.003), with the most advanced fundus autofluorescence phenotypes showing increased pRNFL thickness in this sector.

CONCLUSION

This study expands the genetic landscape of RPGR-associated disease by reporting 3 novel clinically significant variants. We have shown that clinically severe phenotypes are not uncommon among female carriers. Furthermore, we provide novel insights into pRNFL changes observed in RPGR heterozygotes that mimic what has been reported in male patients.

Microperimetry and Adaptive Optics Imaging Reveal Localized Functional and Structural Changes in Asymptomatic RPGR Mutation Carriers

Purpose

Female carriers of RPGR mutations demonstrate no significant retinal dysfunction or structural change despite a characteristic tapetal-like reflex. In this study, we examined localized changes of pointwise sensitivity (PWS) and cone density (CD) using microperimetry (MP) and adaptive optics (AO) imaging in female carriers of RPGR mutations.

Methods

In this cross-sectional case-control study, MP (MAIA, 10-2 test grid) and AO imaging (rtx1) were performed in female carriers of RPGR mutations and unrelated age-matched healthy controls. PWS at 68 loci located 1 degree to 9 degrees away from the preferred retinal locus and CD at 12 loci located 1 degree to 3 degrees away from the foveal center were measured. Severity of defect was defined by standard deviation (SD) from age-matched healthy control means: normal (<1 SD from normal average), moderate defect (1-2 SD from normal average), and severe defect (>2 SD from normal average).

Results

Twelve patients from seven unrelated families were enrolled. Seven patients were asymptomatic, 5 of whom had visual acuity 20/20 or better in both eyes. PWS and CD were available in 12 and 8 patients, respectively. Severe PWS and CD defect in at least 1 test location was observed in 10 of 12 patients and 7 of 8 patients, respectively. Among the five asymptomatic patients who had normal visual acuity, severe PWS and CD defects were observed in three of five and four of five patients, respectively.

Conclusions

MP and AO imaging revealed early functional and structural changes in asymptomatic RPGR mutation carriers and should be considered in clinical assessment of these patients.

Multimodal imaging of retinal findings in syndactyly, telecanthus, anogenital, and renal malformations (STAR) syndrome

Purpose

To report multimodal imaging of novel retinal findings in a case of syndactyly, telecanthus, anogenital, and renal malformations (STAR) syndrome.

Observations

A 5-year old patient with STAR syndrome, an ultra-rare developmental disorder composed of syndactyly, telecanthus, anogenital, and renal malformations, was found to have bilateral macular yellow pigmentary changes and peripheral retinal pigment epithelial changes in a radial pattern highlighted by fundus autofluorescence (FAF) imaging. Optical coherence tomography (OCT) of the macula revealed foveal hypoplasia, ellipsoid zone disruption, and outer retinal atrophy suggestive of a retinal degeneration. OCT angiography found no significant abnormalities, and oral fluorescein angiography revealed staining in areas of atrophy in both eyes.

Conclusions and Importance

This case displays the first report of multimodal imaging of retinal manifestations in STAR syndrome, revealing bilateral foveal hypoplasia, outer retinal macular atrophy, and peripheral retinal pigment epithelial changes. Further studies and long-term follow-up are warranted to determine if patients with STAR syndrome have an underlying progressive retinal degeneration.

Genotype-Phenotype Analysis of RPGR Variations: Reporting of 62 Chinese Families and a Literature Review

Purpose

RPGR is the most common cause of X-linked retinitis pigmentosa (RP), of which female carriers are also frequently affected. The aim of the current study was to explore the RPGR variation spectrum and associated phenotype based on the data from our lab and previous studies.

Methods

Variants in RPGR were selected from exome sequencing data of 7,092 probands with different eye conditions. The probands and their available family members underwent comprehensive ocular examinations. Similar data were collected from previous reports through searches in PubMed, Web of Science, and Google Scholar. Systematic analyses of genotypes, phenotypes and their correlations were performed.

Results

A total of 46 likely pathogenic variants, including nine missense and one in-frame variants in RCC1-like domain and 36 truncation variants, in RPGR were detected in 62 unrelated families in our in-house cohort. In addition, a total of 585 variants, including 491 (83.9%) truncation variants, were identified from the literature. Systematic analysis of variants from our in-house dataset, literature, and gnomAD suggested that most of the pathogenic variants of RPGR were truncation variants while pathogenic missense and in-frame variants were enriched in the RCC1-like domain. Phenotypic variations were present between males and female carriers, including more severe refractive error but better best corrected visual acuity (BCVA) in female carriers than those in males. The male patients showed a significant reduction of BCVA with increase of age and males with exon1-14 variants presented a better BCVA than those with ORF15 variants. For female carriers, the BCVA also showed significant reduction with increase of age, but BCVA in females with exon1-14 variants was not significant difference compared with those with ORF15 variants.

Conclusion

Most pathogenic variants of RPGR are truncations. Missense and in-frame variants located outside of the RCC1-like domain might be benign and the pathogenicity criteria for these variants should be considered with greater caution. The BCVA and refractive error are different between males and female carriers. Increase of age and location of variants in ORF15 contribute to the reduction of BCVA in males. These results are valuable for understanding genotypes and phenotypes of RPGR.

Gene Therapy in Inherited Retinal Diseases: An Update on Current State of the Art

Background: Gene therapy cannot be yet considered a far perspective, but a tangible therapeutic option in the field of retinal diseases. Although still confined in experimental settings, the preliminary results are promising and provide an overall scenario suggesting that we are not so far from the application of gene therapy in clinical settings. The main aim of this review is to provide a complete and updated overview of the current state of the art and of the future perspectives of gene therapy applied on retinal diseases.

Methods: We carefully revised the entire literature to report all the relevant findings related to the experimental procedures and the future scenarios of gene therapy applied in retinal diseases. A clinical background and a detailed description of the genetic features of each retinal disease included are also reported.

Results: The current literature strongly support the hope of gene therapy options developed for retinal diseases. Although being considered in advanced stages of investigation for some retinal diseases, such as choroideremia (CHM), retinitis pigmentosa (RP), and Leber's congenital amaurosis (LCA), gene therapy is still quite far from a tangible application in clinical practice for other retinal diseases.

Conclusions: Gene therapy is an extremely promising therapeutic tool for retinal diseases. The experimental data reported in this review offer a strong hope that gene therapy will be effectively available in clinical practice in the next years.

Fundus Autofluorescence and Clinical Applications

Fundus autofluorescence (FAF) has allowed in vivo mapping of retinal metabolic derangements and structural changes not possible with conventional color imaging. Incident light is absorbed by molecules in the fundus, which are excited and in turn emit photons of specific wavelengths that are captured and processed by a sensor to create a metabolic map of the fundus. Studies on the growing number of FAF platforms has shown each may be suited to certain clinical scenarios. Scanning laser ophthalmoscopes, fundus cameras, and modifications of these each have benefits and drawbacks that must be considered before and after imaging to properly interpret the images. Emerging clinical evidence has demonstrated the usefulness of FAF in diagnosis and management of an increasing number of chorioretinal conditions, such as age-related macular degeneration, central serous chorioretinopathy, retinal drug toxicities, and inherited retinal degenerations such as retinitis pigmentosa and Stargardt disease. This article reviews commercial imaging platforms, imaging techniques, and clinical applications of FAF.

Autofluorescence in female carriers with choroideremia: A familial case with a novel mutation in the CHM gene

BACKGROUND

Choroideremia is an X-linked chorioretinal dystrophy caused by mutations in the CHM gene. The main differential diagnosis is X-linked retinitis pigmentosa. Clinically, male patients that are affected by these two diseases have similar symptoms. This work aims to report a familial case of choroideremia initially diagnosed as X-linked retinitis pigmentosa with a novel mutation in the CHM gene, and the relevance of fundus autofluorescence (FAF) in female carriers.

MATERIALS AND METHODS

A complete ophthalmological evaluation was done in a 37-year-old woman and her 53-year-old maternal uncle; the uncle had been diagnosed previously with X-linked retinitis pigmentosa. A visual field test, FAF imaging, full-field electroretinography, and a genetic test were performed.

RESULTS

In the proband, the fundoscopy revealed diffuse changes in the retinal pigment epithelium in both eyes, and the FAF showed a speckled pattern of low- and high-density. The maternal uncle's ophthalmological evaluation showed choroidal and retinal atrophy consistent with choroideremia. The molecular analysis revealed a pathogenic variant in the CHM gene, c.190-1 G > T.

CONCLUSIONS

In female carriers of choroideremia and X-linked retinitis pigmentosa, differential diagnosis may be challenging. A speckled pattern of low- and high-density in autofluorescence is commonly found in female carriers of choroideremia. FAF is a powerful tool for making a correct clinical diagnosis because the pattern in FAF is much more apparent than the visible retinal changes obtained by fundoscopy. Although it is crucial to perform molecular analysis to confirm the diagnosis, FAF is useful when genetic testing may not be readily available.

CELLULAR IMAGING OF THE TAPETAL-LIKE REFLEX IN CARRIERS OF RPGR-ASSOCIATED RETINOPATHY

PURPOSE

To examine the features of the tapetal-like reflex (TLR) in female carriers of RPGR-associated retinopathy by means of adaptive optics scanning light ophthalmoscopy (AOSLO) and spectral domain optical coherence tomography.

METHODS

Nine molecularly confirmed RPGR carriers and three healthy controls underwent ocular examination and the following retinal imaging modalities: color photography, near-infrared reflectance, fundus autofluorescence, spectral domain optical coherence tomography, and AOSLO. After identifying TLR areas across all imaging modalities, normalized local contrast of outer retinal bands on spectral domain optical coherence tomography was calculated and AOSLO-acquired photoreceptor mosaic analysis was performed.

RESULTS

Seven carriers had TLR areas, which colocalized with increased rod photoreceptor reflectivity on confocal AOSLO and reduced cone photoreceptor densities. Parafoveal TLR areas also exhibited reduced local contrast (i.e., increased reflectivity) of the outer retinal bands on spectral domain optical coherence tomography (inner segment ellipsoid zone and outer segment interdigitation zone). Healthy controls did not show TLR.

CONCLUSION

The cellular resolution provided by AOSLO affords the characterization of the photoreceptor mosaic in RPGR carriers with a TLR. Features revealed include reduced cone density, increased cone inner segment diameter, and increased rod outer segment reflectivity.

Reviewing the Role of Ultra-Widefield Imaging in Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRD) are a heterogeneous group of rare chronic disorders caused by genetically determined degeneration of photoreceptors and retinal pigment epithelium cells. Ultra-widefield (UWF) imaging is a useful diagnostic tool for evaluating retinal integrity in IRD, including Stargardt disease, retinitis pigmentosa, cone dystrophies, and Best vitelliform dystrophy. Color or pseudocolor and fundus autofluorescence images obtained with UWF provide previously unavailable information on the retinal periphery, which correlates well with visual field measurement or electroretinogram. Despite unavoidable artifacts of the UWF device, the feasibility of investigations in infants and in patients with poor fixation makes UWF imaging a precious resource in the diagnostic armamentarium for IRD.

Wide-field fundus autofluorescence imaging in patients with hereditary retinal degeneration: a literature review

Background

Inherited retinal degeneration (IRD) refers to a heterogenous group of progressive diseases that cause death of photoreceptor cells and subsequent vision loss. These diseases often affect the peripheral retina, objective evaluation of which has been difficult until recently. Fundus autofluorescence (FAF) is a non-invasive retinal imaging technique that depicts the distribution of intrinsic fluorophores in the retina. The primary source of retinal autofluorescence is lipofuscin, which is contained in the retinal pigment epithelium (RPE). Excessive accumulation of lipofuscin and a window defect attributable to loss of photoreceptor pigment result in increased FAF whereas loss of the RPE results in decreased FAF. These changes can be seen during the course of IRD.

Mainbody

While conventional modalities are limited in their angle of view, recent technologic advances, known as wide-field and ultra-widefield FAF imaging, have enabled visualization of the far peripheral retina. Although clinical application of this technique in patients with IRD is still in its infancy, some studies have already indicated its usefulness. For example, an area with decreased FAF correlates well with a visual field defect in an eye with retinitis pigmentosa (RP) or cone-rod dystrophy. An abnormal FAF pattern may help in the diagnosis of IRD and associated diseases. In addition, female carriers of X-linked RP and female choroideremia show characteristic appearance. Conversely, absence of abnormal FAF despite severe retinal degeneration helps differentiation of cancer-associated retinopathy.

Conclusion

This paper reviews the principles of FAF, wide-field imaging, and findings in specific diseases. Wide-field imaging, particularly wide-field FAF, will provide further information for the characteristics, prognosis, and pathogenesis of IRD.

X-linked Retinitis Pigmentosa in Japan: Clinical and Genetic Findings in Male Patients and Female Carriers

X-linked retinitis pigmentosa (XLRP) is a type of severe retinal dystrophy, and female carriers of XLRP demonstrate markedly variable clinical severity. In this study, we aimed to elucidate the clinical findings of male patients with and female carriers of XLRP in a Japanese cohort and demonstrate the genetic contribution. Twelve unrelated families (13 male patients, 15 female carriers) harboring pathogenic mutations in RPGR or RP2 were included, and comprehensive ophthalmic examinations were performed. To identify potential pathogenic mutations, targeted next-generation sequencing was employed. Consequently, we identified 11 pathogenic mutations, of which five were novel. Six and five mutations were detected in RPGR and RP2, respectively. Only one mutation was detected in ORF15. Affected male patients with RP2 mutations tended to have lower visual function than those with RPGR mutations. Female carriers demonstrated varying visual acuities and visual fields. Among the female carriers, 92% had electroretinographical abnormalities and 63% had a radial autofluorescent pattern, and the carriers who had higher myopia showed worse visual acuity and more severe retinal degeneration. Our results expand the knowledge of the clinical phenotypes of male patients with and female carriers of XLRP and suggest the possibility that RP2 mutations are relatively highly prevalent in Japan.

Next-generation sequencing identifies unexpected genotype-phenotype correlations in patients with retinitis pigmentosa

Retinitis pigmentosa (RP) is an inherited degenerative disease causing severe retinal dystrophy and visual impairment mainly with onset in infancy or adolescence. Targeted next-generation sequencing (NGS) has become an efficient tool to encounter the enormous genetic heterogeneity of diverse retinal dystrophies, including RP. To identify disease-causing mutations in unselected, consecutive RP patients, we conducted Sanger sequencing of genes commonly involved in the suspected genetic RP subtype, followed by targeted large-panel NGS if no mutation was identified, or NGS as primary analysis. A high (70%) detection rate of disease-causing mutations was achieved in a large cohort of 116 unrelated patients. About half (48%) of the solved RP cases were explained by mutations in four genes: RPGR, EYS, PRPF31 and USH2A. Overall, 110 different mutations distributed across 30 different genes were detected, and 46 of these mutations were novel. A molecular diagnosis was achieved in the majority (82–100%) of patients if the family history was suggestive for a particular mode of inheritance, but only in 60% in cases of sporadic RP. The diagnostic potential of extensive molecular analysis in a routine setting is also illustrated by the identification of unexpected genotype-phenotype correlations for RP patients with mutations in CRX, CEP290, RPGRIP1, MFSD8. Furthermore, we identified numerous mutations in autosomal dominant (PRPF31, PRPH2, CRX) and X-linked (RPGR) RP genes in patients with sporadic RP. Variants in RP2 and RPGR were also found in female RP patients with apparently sporadic or dominant disease. In summary, this study demonstrates that massively parallel sequencing of all known retinal dystrophy genes is a valuable diagnostic approach for RP patients.

Ultra-Widefield Fundus Autofluorescence Imaging of Patients with Retinitis Pigmentosa: A Standardized Grading System in Different Genotypes

PURPOSE

To report a genotype-phenotype correlation study of patients with retinitis pigmentosa (RP) based on ultra-widefield (UWF) fundus autofluorescence (FAF) imaging.

DESIGN

Case series.

PARTICIPANTS

Thirty-four patients with RP.

METHODS

This retrospective study included RP patients with confirmed causative genetic variants and UWF FAF imaging data. Qualitative grading criteria including the pattern of macular abnormal autofluorescence, decreased autofluorescence (DAF), and its extent and distribution were applied to evaluate the genotype-phenotype correlation.

MAIN OUTCOME MEASURES

The main parameters measured were increased or decreased patterns and extent of autofluorescence.

RESULTS

Thirty-four unrelated patients 38±19 years of age (range, 9-82 years) were enrolled. Mutations in 17 different genes were detected in patients, including 7 patients having mutations in USH2A, 4 in DHDDS, 4 in RPGR, 3 in PRPF31, and 3 in RP1. Patients with nummular DAF and widespread DAF were significantly older (59±14 years and 56±19 years, respectively). All 3 patients with PRPF31 mutations showed an abnormal macular ring hyperautofluorescence and a circular pattern of coarse DAF distributed in Early Treatment Diabetic Retinopathy Study fields 1, 2, and 3 with sparing of the far periphery. In other genotypes, no specific DAF or macular abnormal autofluorescence pattern could be discerned.

CONCLUSIONS

Specific UWF FAF characteristics in RP patients were correlated strongly with patient age and stage of the disease. Particular UWF FAF characteristics were found to be more prominent in a unique genotype.