Optic Nerve Head, Retinal Nerve Fiber Layer, and Macular Thickness Measurements in Young Patients with Retinitis Pigmentosa

Spatial Transcriptomic Analysis Reveals Regional Transcript Changes in Early and Late Stages of rd1 Model Mice with Retinitis Pigmentosa

Retinitis pigmentosa (RP) is the leading cause of inherited blindness with a genetically heterogeneous disorder. Currently, there is no effective treatment that can protect vision for those with RP. In recent decades, the rd1 mouse has been used to study the pathological mechanisms of RP. Molecular biological studies using rd1 mice have clarified the mechanism of the apoptosis of photoreceptor cells in the early stage of RP. However, the pathological changes in RP over time remain unclear. The unknown pathology mechanism of RP over time and the difficulty of clinical treatment make it urgent to perform more refined and spatially informed molecular biology studies of RP. In this study, spatial transcriptomic analysis is used to study the changes in different retinal layers of rd1 mice at different ages. The results demonstrate the pattern of photoreceptor apoptosis between rd1 mice and the control group. Not only was oxidative stress enhanced in the late stage of RP, but it was accompanied by an up-regulation of the VEGF pathway. Analysis of temporal kinetic trends has further identified patterns of changes in the key pathways of the early and late stages, to help understand the important pathogenesis of RP. Overall, the application of spatial transcriptomics to rd1 mice can help to elucidate the important pathogenesis of RP involving photoreceptor apoptosis and retinal remodeling.

Searching for Effective Methods of Diagnosing Nervous System Lesions in Patients with Alström and Bardet-Biedl Syndromes

Bardet-Biedl syndrome (BBS) and Alström syndrome (ALMS) are rare multisystem diseases with an autosomal recessive mode of inheritance and genetic heterogeneity, characterized by visual impairment, hearing impairment, cardiomyopathy, childhood obesity, and insulin resistance. The purpose of our study was to evaluate the indicators of nervous system changes occurring in patients with ALMS and BBS using optical coherence tomography (OCT) and magnetic resonance spectroscopy (MRS) methods compared to a group of healthy subjects. The OCT results showed significantly lower macular thickness in the patient group compared to the control group (p = 0.002). The MRS study observed differences in metabolite levels between the study and control groups in brain areas such as the cerebellum, thalamus, and white matter. After summing the concentrations from all areas, statistically significant results were obtained for N-acetylaspartate, total N-acetylaspartate, and total creatine. Concentrations of these metabolites were reduced in ALMS/BBS patients by 38% (p = 0.0004), 35% (p = 0.0008), and 28% (p = 0.0005), respectively. Our results may help to understand the pathophysiology of these rare diseases and identify strategies for new therapies.

Retinitis Pigmentosa: Progress in Molecular Pathology and Biotherapeutical Strategies

Retinitis pigmentosa (RP) is genetically heterogeneous retinopathy caused by photoreceptor cell death and retinal pigment epithelial atrophy that eventually results in blindness in bilateral eyes. Various photoreceptor cell death types and pathological phenotypic changes that have been disclosed in RP demand in-depth research of its pathogenic mechanism that may account for inter-patient heterogeneous responses to mainstream drug treatment. As the primary method for studying the genetic characteristics of RP, molecular biology has been widely used in disease diagnosis and clinical trials. Current technology iterations, such as gene therapy, stem cell therapy, and optogenetics, are advancing towards precise diagnosis and clinical applications. Specifically, technologies, such as effective delivery vectors, CRISPR/Cas9 technology, and iPSC-based cell transplantation, hasten the pace of personalized precision medicine in RP. The combination of conventional therapy and state-of-the-art medication is promising in revolutionizing RP treatment strategies. This article provides an overview of the latest research on the pathogenesis, diagnosis, and treatment of retinitis pigmentosa, aiming for a convenient reference of what has been achieved so far.

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

Purpose

To investigate multimodal retinal imaging characteristics including the retinal nerve fiber layer (RNFL) thickness in patients with RPGR-associated retinitis pigmentosa (RP).

Methods

This cross-sectional case–control study included 17 consecutive patients (median age, 21 years) with RPGR-associated RP who underwent retinal imaging including optical coherence tomography (OCT), short-wavelength fundus autofluorescence (AF) imaging, and RNFL scans centered on the optic disc. RNFL thickness was manually segmented and compared to clinical and imaging parameters including the transfoveal ellipsoid zone (EZ) width, the horizontal diameter of the macular hyperautofluorescent ring. RNFL thickness was compared to 17 age- and sex-matched controls.

Results

In patients with RPGR-associated RP, the EZ width (R² = 0.65), the central hyperautofluorescent ring on AF images (R² = 0.72), and visual acuity (R² = 0.68) were negatively correlated with age. In comparison to controls, a significantly (p < 0.0001) increased global RNFL thickness was identified in RPGR-associated RP, which was, however, less pronounced in progressed disease as indicated by the EZ width or the diameter of the central hyperautofluorescent ring.

Conclusions

This study describes retinal characteristics in patients with RPGR-associated RP including a pronounced peripapillary RNFL thickness compared to healthy controls. These results contribute to the knowledge about imaging biomarkers in RP, which might be of interest for therapeutic approaches such as gene replacement therapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-021-05233-w.

Glial proliferation and atrophy: Two poles of optic disc in patients with retinitis pigmentosa

Purpose

To clarify the difference of retinal nerve fiber layer (RNFL) thicknesses between patients with retinitis pigmentosa (RP) and normal subjects.

Methods

The study included right eyes of 30 patients with non-late-stage RP, which had a waxy pallor in OD, attenuation in retinal arterioles, and midperipheral bone spicule pigmentary changes. To compare the RNFL analysis with normal subjects, the right eyes of 30 age- and gender-matched healthy subjects were included as a control group.

Results

There were no differences between the RP and control groups in terms of demographic and baseline characteristics (P > 0.05, for all). The mean temporal quadrant RNFL thickness was 102.9 ± 31.7 μm (43–222) in the RP group and 72.4 ± 11.8 μm (51–90) in the control group (P < 0.001). The mean nasal quadrant RNFL thickness was 57.6 ± 33.7 μm (21–140) in the RP and 75.0 ± 14.1 μm (56–132) in the control group (P < 0.001). There were no significant RNFL thickness differences between the groups in other sectors and globally (P > 0.05, for all). There was no significant correlation between temporal RNFL thickening and ageing (r = −0.136, P = 0.196) while there was a significant correlation between nasal RNFL thinning and ageing (r = −0.274, P = 0.047).

Conclusions

RNFL is thicker in temporal quadrants and thinner in nasal quadrants in non-late stage RP. Age-related decreases in RNFL thickness occurred earlier in the nasal quadrant and RNFL thickening in the temporal quadrant occurred earlier than this global thinning.

Correlation between Visual Function and Structural Characteristics of the Macula in Advanced Retinitis Pigmentosa

We aimed to correlate the visual function and structural characteristics of the retina and choroid in advanced retinitis pigmentosa (RP) patients. A cross-sectional, retrospective review was conducted of medical records of 149 RP patients who reported visual field constriction on a central 30-2 Humphrey visual field chart. Using spectral domain-optical coherence tomography, central foveal thickness (CFT), ellipsoid zone (EZ) length, macular volume (MV), and submacular choroidal thickness (SMChT) were measured. A control cohort (68 eyes of 68 patients) was included for comparing the macular structure. Quantitative correlations between visual function indices [visual field index (VFI) and best-corrected visual acuity (BCVA)] and structural indices (CFT, EZ length, and SMChT) were evaluated. Mean age was 46.3 ± 15.5 years; mean illness duration was 60.7 ± 60.0 months. SMChT was thinner than that in normal controls. Per Pearson's correlation, BCVA and VFI exhibited a progressive worsening related to age and disease duration. In multivariate linear regression, BCVA and VFI were significantly correlated with CFT, EZ length, and MV at the central 1-mm area. Among RP patients with visual field constriction within 30°, VFI and BCVA closely correlate with the degree of retinal structural change, including the CFT, EZ length, and MV. SMChT uniformly decreased in this study population and exhibited no significant correlation with BCVA or VFI degree.

Peripapillary Retinal Nerve Fiber Layer Thicknesses Did Not Change in Long-term Hydroxychloroquine Users

Purpose

To evaluate changes in the peripapillary retinal nerve fiber layer (RNFL) thicknesses using spectral-domain optical coherence tomography (SD-OCT) in hydroxychloroquine (HCQ) users.

Methods

The medical records of HCQ users were retrospectively reviewed. In these HCQ users, an automated perimetry, fundus autofluorescence photography, and SD-OCT with peripapillary RNFL thickness measurements were performed. The peripapillary RNFL thicknesses were compared between the HCQ users and the control groups. The relationships between the RNFL thicknesses and the duration or cumulative dosage of HCQ use were analyzed.

Results

This study included 77 HCQ users and 20 normal controls. The mean duration of HCQ usage was 63.6 ± 38.4 months, and the cumulative dose of HCQ was 528.1 ± 3.44 g. Six patients developed HCQ retinopathy. Global and six sectoral RNFL thicknesses of the HCQ users did not significantly decrease compared to those of the normal controls. No significant correlation was found between the RNFL thickness and the duration of use or cumulative dose. The eyes of those with HCQ retinopathy had temporal peripapillary RNFL thicknesses significantly greater than that of normal controls.

Conclusions

The peripapillary RNFL thicknesses did not change in the HCQ users and did not correlate with the duration of HCQ use or cumulative doses of HCQ. RNFL thickness is not a useful biomarker for the early detection of HCQ retinal toxicity.

Non-syndromic retinitis pigmentosa

Retinitis pigmentosa (RP) encompasses a group of inherited retinal dystrophies characterized by the primary degeneration of rod and cone photoreceptors. RP is a leading cause of visual disability, with a worldwide prevalence of 1:4000. Although the majority of RP cases are non-syndromic, 20-30% of patients with RP also have an associated non-ocular condition. RP typically manifests with night blindness in adolescence, followed by concentric visual field loss, reflecting the principal dysfunction of rod photoreceptors; central vision loss occurs later in life due to cone dysfunction. Photoreceptor function measured with an electroretinogram is markedly reduced or even absent. Optical coherence tomography (OCT) and fundus autofluorescence (FAF) imaging show a progressive loss of outer retinal layers and altered lipofuscin distribution in a characteristic pattern. Over the past three decades, a vast number of disease-causing variants in more than 80 genes have been associated with non-syndromic RP. The wide heterogeneity of RP makes it challenging to describe the clinical findings and pathogenesis. In this review, we provide a comprehensive overview of the clinical characteristics of RP specific to genetically defined patient subsets. We supply a unique atlas with color fundus photographs of most RP subtypes, and we discuss the relevant considerations with respect to differential diagnoses. In addition, we discuss the genes involved in the pathogenesis of RP, as well as the retinal processes that are affected by pathogenic mutations in these genes. Finally, we review management strategies for patients with RP, including counseling, visual rehabilitation, and current and emerging therapeutic options.

Ganglion cell-inner plexiform layer and retinal nerve fibre layer changes within the macula in retinitis pigmentosa: a spectral domain optical coherence tomography study

PURPOSE

To investigate how macular ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) thicknesses within the macula change with retinitis pigmentosa (RP) severity.

METHODS

Spectral domain optical coherence tomography (SD-OCT) was used to examine 177 patients with RP and 177 normal controls. An optical coherence tomography (OCT) line scan was used to grade RP severity. Retinitis pigmentosa (RP) was categorized as more advanced if there was no identifiable inner segment ellipsoid (ISe) band (NISE) and as less advanced if an ISe band could be identified and peripheral loss of ISe was apparent (IISE). Ganglion cell-inner plexiform layer (GCIPL) and RNFL thicknesses were manually measured on OCT images and analysed. Pearson's correlation analyses were used to examine correlations between GCIPL thickness, RNFL thickness, visual acuity (VA) and visual field extent in patients and controls.

RESULTS

Ganglion cell-inner plexiform layer (GCIPL) was significantly thicker in IISE than in control eyes (p < 0.001), but significantly thinner in NISE than in IISE eyes (p < 0.001) in both horizontal and vertical OCT scans. Retinal nerve fibre layer (RNFL) was significantly thicker in eyes with IISE and NISE than in control eyes in both horizontal and vertical meridians (all p < 0.001). Ganglion cell-inner plexiform layer (GCIPL) thickness showed a weak positive correlation with vision, and RNFL thickness showed a weak negative correlation with vision and visual field extent.

CONCLUSION

Based on these results, the inner retina, including the GCIPL and RNFL, maintains its gross integrity longer than the photoreceptor layer in RP. Additionally, thickening of the inner retina may have some functional implications in patients with RP.

Spectral-domain optical coherence tomography reveals prelaminar membranes in optic nerve head pallor in eyes with retinitis pigmentosa

PURPOSE

To determine the relationship between prelaminar structural changes of the optic nerve head (ONH) and optic nerve waxy pallor in retinitis pigmentosa (RP) using spectral-domain optical coherence tomography (SD-OCT) and fundus photography.

METHODS

An observational cross-sectional case control study of patients with RP with and without ONH waxy pallor and controls. Subjects underwent clinical examination, fundus photography, and SD-OCT raster imaging of the ONH. Four independent specialists reviewed the images in a masked fashion.

RESULTS

Fifty-five eyes of 31 subjects with RP and 28 eyes of 14 controls were included. Optic nerve head waxy pallor was seen in 29 RP eyes (52.7 %) and none in controls. SD-OCT showed a hyper-reflective structure suggestive of a glial membrane-like structure on the surface of ONH in 16 of RP eyes (55.1 %). In the RP group, there was a significant positive correlation between the ONH pallor and the presence of a prelaminar structure (p = 0.006).

CONCLUSIONS

There is a presence of glial membrane-like structures on the optic nerve head surface in eyes with RP compared to healthy eyes. As the presence of glial membranes correlated with the presence of ONH waxy pallor, in such cases these membranes might be responsible for ONH waxy pallor.

The Structure-Function Relationship between Macular Morphology and Visual Function Analyzed by Optical Coherence Tomography in Retinitis Pigmentosa

Purpose. To evaluate the relationship between macular microstructures and visual function in retinitis pigmentosa (RP). Method. Fourier domain optical coherence tomography (FD-OCT) and Goldmann perimetry were used to examine 100 eyes of 100 RP patients. The preserved photoreceptor outer segment (PROS) length was measured at the horizontal and vertical high definition line scans. The PROS area was calculated from slab image and line scans simultaneously. The visual field area (VFA) was quantified. Each retinal thickness was measured: inner retina (IRT), outer retina (ORT), subfoveal choroidal thickness (SFCT), and central retinal thickness (CRT). Results. The PROS area values acquired differently were consistent. The VFA was related significantly to the CRT, ORT, PROS length (vertical and horizontal), and PROS area (line scan and slab image). Visual acuity was correlated with the CRT, ORT, IRT, PROS length (horizontal and vertical), and PROS area (line scan and slab image) significantly. Multiple linear regression analysis revealed that the PROS horizontal length and ORT were related to the VFA and visual acuity, respectively. Conclusion. Among the macular microstructures, the PROS horizontal length and the ORT were most correlated with VFA and visual acuity, respectively. However, SFCT is not related to visual function.

Longitudinal analysis of the peripapillary retinal nerve fiber layer thinning in patients with retinitis pigmentosa

PURPOSE

To investigate longitudinal changes in peripapillary retinal nerve fiber layer (RNFL) thickness in patients with retinitis pigmentosa (RP).

METHODS

We re-examined 103 RP patients whose RNFL thickness was previously examined and reported. RNFL thickness was measured using Stratus optical coherence tomography and was compared with the previous measurements. The results were also compared with that of previously reported normal subjects. Association between the decrease rate and visual acuity, and visual field was also investigated.

RESULTS

The mean follow-up period was 56.9 months. After excluding the patients in whom RNFL images were of poor quality, 88 patients were eventually analyzed. The average RNFL thickness decreased from 105.8 to 98.2 μm during the period, with the average rate of decrease being 1.6 μm/year. The decrease in RNFL was more evident in superior and inferior sectors. Cross-sectional linear regression analysis also revealed an age-dependent decrease in RNFL, with the slower rate of decrease being 0.94 μm/year. The decrease in RNFL thickness was significantly faster than that reported in normal subjects. The decrease rate was not associated with visual functions.

CONCLUSION

Age-dependent RNFL thinning occurs at a faster rate in RP patients as compared with that in normal subjects. The result supports the notion that pathologic changes involve inner retina as well as outer retina in eyes with RP. Considering the discrepancy in the rate of RNFL thinning estimated from trend analysis and longitudinal measurement, care should be taken when interpreting the result of cross-sectional analysis.