Analysis of imaging biomarkers and retinal nerve fiber layer thickness in RPGR-associated retinitis pigmentosa

The Exponential Constriction Model of the Ellipsoid Zone in Taiwanese Individuals With RPGR-Related X-Linked Retinitis Pigmentosa

Purpose

This study documents the natural disease progression and genotype-phenotype correlation in RPGR-related retinitis pigmentosa (RP) in the Taiwanese population.

Methods

A retrospective analysis was conducted on individuals with molecularly confirmed RPGR-related disease-causing variant(s). Demographics, best-corrected visual acuity (BCVA), spherical equivalent (SE), fundus autofluorescence, and optical coherence tomography were assessed.

Results

Fifty-two individuals from 31 families were diagnosed with RPGR-related disease-causing variant(s). Mean follow-up time was 4.2 years. Among 21 genetic variants, 67% involved the open reading frame 15 region (ORF15) variant, and 33% were Exon 1-14 variants. Male patients (69%) had a mean BCVA of 0.9 logMAR and SE of -3.8 D in the right eye and -3.0 D in the left eye, with high myopia in 19% to 20%. BCVA progression was 0.031 logMAR/year in the ORF15 group (P < 0.001) and 0.011 logMAR/year (P = 0.457) in the Exon 1-14 group. An exponential decay model revealed rapid ellipsoid zone (EZ) constriction during childhood in the ORF15 group. Female patients/carriers (31%) had a mean BCVA of 0.3 logMAR and SE of -4.3D, with high myopia of 31% in the right eye and 46% in the left eye. Among symptomatic females, 73% exhibited clinically significant disease. The most common mutation was the c.2592dup variant (15%).

Conclusions

This first longitudinal analysis of RPGR-related RP in Taiwan presents a predictive model of EZ constriction. Findings suggest earlier onset in Exon 1-14 variants and a tendency for faster progression in the ORF15 group, informing insights for genetic therapy development and disease management.

Retinal Thickness Analysis Using Optical Coherence Tomography: Diagnostic and Monitoring Applications in Retinal Diseases

Retinal thickness analysis using optical coherence tomography (OCT) has become an indispensable tool in retinal disease management, providing high-resolution quantitative data for diagnosis, monitoring, and treatment planning. This analysis has been found to be particularly useful for both diagnostic and monitoring purposes across a wide range of retinal diseases, enabling precise disease characterization and treatment evaluation. This paper explores its applications across major retinal conditions, including age-related macular degeneration, diabetic retinopathy, retinal vein occlusion, and inherited retinal diseases. Emerging roles in other diseases such as neurodegenerative diseases and retinal drug toxicity are also highlighted. Despite challenges such as variability in measurements, segmentation errors, and interpretation difficulties, advancements in artificial intelligence and machine learning have significantly improved accuracy and efficiency. The integration of retinal thickness analysis with telemedicine platforms and standardized protocols further underscores its potential in delivering personalized care and enabling the early detection of ocular and systemic diseases. Retinal thickness analysis continues to play a pivotal and growing role in both clinical practice and research, bridging the gap between ophthalmology and broader medical fields.

[Opticopathies in the differential diagnosis of retinal diseases - part 2]

Due to the close anatomical, functional and trophic relationships between the optic nerve and retina, a wide variety of diseases affecting both structures have reciprocal effects on each other, which must be considered in the differential diagnosis to avoid misdiagnosis. Therefore, it is essential to assess pathological changes in both structures in context to differentiate the type and location of the primary lesion from its consequences, as well as to correctly classify coincidences and disease-specific lesion patterns in both organ components.This article highlights the typical symptom constellations and lesion patterns of optic neuropathies and retinopathies. An attempt is made to identify the reciprocal characteristic relationships of the respective lesions in both structures in various disease groups, as well as to present their respective roles in the differential diagnosis.In this second part, acquired optic neuropathies in the context of vascular and systemic diseases and possible accompanying retinal findings, as well as symptom constellations and courses, are differentiated, discussing arteritic and non-arteritic (anterior) optic neuropathies, their causes and differential diagnosis. The combined involvement of the optic nerve and retina in the context of posterior infectious and non-infectious uveitis is also shown. Finally, various dysgenetic optic neuropathies, their differentiation and possible retinal sequelae are presented.It is demonstrated and exemplified how important it is in general, but also specifically in regard to the disease groups discussed in this article, to have a careful and targeted diagnostic approach in each case, considering both the retinal and optic nerve findings, in order to avoid misdiagnosis.

[Opticopathies in the differential diagnosis of retinal diseases - part 1]

Due to the close anatomical, functional and trophic relationships between the optic nerve and retina, a wide variety of diseases affecting both structures have reciprocal effects on each other, which must be considered in the differential diagnosis to avoid misdiagnosis. Therefore, it is essential to assess pathological changes in both structures in context to differentiate the type and location of the primary lesion from its consequences, as well as to correctly classify coincidences and disease-specific lesion patterns in both organ components.This article highlights the typical symptom constellations and lesion patterns of optic neuropathies and retinopathies. An attempt is made to identify the reciprocal characteristic relationships of the respective lesions in both structures in various disease groups, as well as to present their respective roles in the differential diagnosis.In the first part of the article, typical optic neuropathies in the context of various syndromic and non-syndromic retinal dystrophies are initially examined. Subsequently, the relationships between different hereditary and acquired mitochondriopathic optic neuropathies and possible accompanying retinal changes are analysed, and their pathogenesis and relevant differential diagnoses are discussed.It is demonstrated and exemplified how important it is in general, but also specifically in regard to the disease groups discussed in this article, to have a careful and targeted diagnostic approach in each case, considering both the retinal and optic nerve findings, in order to avoid misdiagnosis.

Retinitis pigmentosa GTPase regulator-related retinopathy and gene therapy

Retinitis pigmentosa GTPase regulator (RPGR)-related retinopathy is a retinal dystrophy inherited in a X-linked recessive manner that typically causes progressive visual loss starting in childhood with severe visual impairment by the fourth decade of life. It manifests as an early onset and severe form of retinitis pigmentosa. There are currently no effective treatments for RPGR-related retinopathy; however, there are multiple clinical trials in progress exploring gene augmentation therapy aimed at slowing down or halting the progression of disease and possibly restoring visual function. This review focuses on the molecular biology, clinical manifestations, and the recent progress of gene therapy clinical trials.

A multidisciplinary approach to inherited retinal dystrophies from diagnosis to initial care: a narrative review with inputs from clinical practice

BACKGROUND

Non-syndromic inherited retinal dystrophies (IRDs) such as retinitis pigmentosa or Leber congenital amaurosis generally manifest between early childhood and late adolescence, imposing profound long-term impacts as a result of vision impairment or blindness. IRDs are highly heterogeneous, with often overlapping symptoms among different IRDs, and achieving a definite diagnosis is challenging. This narrative review provides a clinical overview of the non-syndromic generalized photoreceptor dystrophies, particularly retinitis pigmentosa and Leber congenital amaurosis. The clinical investigations and genetic testing needed to establish a diagnosis are outlined, and current management approaches are discussed, focusing on the importance of the involvement of an interdisciplinary team from diagnosis and initial care to long-term follow-up and support.

RESULTS

The effective management of IRDs requires a multidisciplinary, and ideally interdisciplinary, team of experts knowledgeable about IRDs, with experienced professionals from fields as diverse as ophthalmology, neuropsychiatry, psychology, neurology, genetics, orthoptics, developmental therapy, typhlology, occupational therapy, otolaryngology, and orientation and mobility specialties. Accurate clinical diagnosis encompasses a range of objective and subjective assessments as a prerequisite for the genetic testing essential in establishing an accurate diagnosis necessary for the effective management of IRDs, particularly in the era of gene therapies. Improvements in genome sequencing techniques, such as next-generation sequencing, have greatly facilitated the complex process of determining IRD-causing gene variants and establishing a molecular diagnosis. Genetic counseling is essential to help the individual and their family understand the condition, the potential risk for offspring, and the implications of a diagnosis on visual prognosis and treatment options. Psychological support for patients and caregivers is important at all stages of diagnosis, care, and rehabilitation and is an essential part of the multidisciplinary approach to managing IRDs. Effective communication throughout is essential, and the patient and caregivers' needs and expectations must be acknowledged and discussed.

CONCLUSION

As IRDs can present at an early age, clinicians need to be aware of the clinical signs suggesting visual impairment and follow up with multidisciplinary support for timely diagnoses to facilitate appropriate therapeutic or rehabilitation intervention to minimize vision loss.

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.

Morphological and Morphometric Analysis of Canine Choroidal Layers Using Spectral Domain Optical Coherence Tomography

The choroid, a multifunctional tissue, has been the focus of research interest for many scientists. Its morphology and morphometry facilitate an understanding of pathological processes within both the choroid and retina. This study aimed to determine the choroidal layer thicknesses in healthy, mixed-breed mesocephalic dogs, both male (M) and female (F), using spectral domain optical coherence tomography (SD-OCT) with radial, cross-sectional, and linear scans. The dogs were divided into two groups based on age: middle-aged (MA) and senior (SN). Thicknesses of choroidal layers, namely RPE-Bruch's membrane-choriocapillaris complex (RPE-BmCc) with tapetum lucidum in the tapetal fundus, the medium-sized vessel layer (MSVL), and the large vessel layer with lamina suprachoroidea (LVLS), as well as whole choroidal thickness (WCT), were measured manually using the caliper function integrated into the OCT software. Measurement was performed dorsally and ventrally at a distance of 5000-6000 μm temporally and nasally at a distance of 4000-7000 μm to the optic disc on enhanced depth scans. The measurements were conducted temporally and nasally in both the tapetal (temporal tapetal: TempT, nasal tapetal: NasT) and nontapetal (temporal nontapetal: TempNT, nasal nontapetal: NasNT) fundus. The ratio of the MSVL thickness to the LVLS thickness for each region was calculated. In all examined dogs, the RPE-BmCc in the dorsal (D) region and MSVL in the Tt region were significantly thicker than those in the other regions. The MSVL was thinner in the ventral (V) region than in the D, TempT, TempNT and NasT regions. The MSVL was significantly thinner in the NasNT region than in the D region. LVLS thickness and WCT were significantly greater in the D and TempT regions than those in the other regions and significantly lesser in the V region than those in the other regions. The MSVL-to-LVLS thickness ratio did not differ between the age groups. Our results reveal that the choroidal thickness profile does not depend on age. Our findings can be used to document the emergence and development of various choroidal diseases in dogs in the future.

Investigation of Structural Alterations in Inherited Retinal Diseases: A Quantitative SD-OCT-Analysis of Retinal Layer Thicknesses in Light of Underlying Genetic Mutations

Inherited retinal diseases can result from various genetic defects and are one of the leading causes for blindness in the working-age population. The present study aims to provide a comprehensive description of changes in retinal structure associated with phenotypic disease entities and underlying genetic mutations. Full macular spectral domain optical coherence tomography scans were obtained and manually segmented in 16 patients with retinitis pigmentosa, 7 patients with cone−rod dystrophy, and 7 patients with Stargardt disease, as well as 23 age- and sex-matched controls without retinal disease, to assess retinal layer thicknesses. As indicated by generalized least squares models, all IRDs were associated with retinal thinning (p < 0.001), especially of the outer nuclear layer (ONL, p < 0.001). Except for the retinal nerve fiber layer, such thinning was associated with a reduced visual acuity (p < 0.001). These advances in our understanding of ultrastructural retinal changes are important for the development of gene-, cell-, and optogenetic therapy. Longitudinal studies are warranted to describe the temporal component of those changes.