Optical coherence tomography in the evaluation of retinitis pigmentosa

Hyperreflective ganglion cell layer band in a large cohort of non-syndromic retinitis pigmentosa: Frequency and clinical correlations

PURPOSE

Recently, an 'hyperreflective ganglion cell layer band' (HGB) has been described on spectral-domain optical coherence tomography (SD-OCT) in a subset of patients with retinitis pigmentosa (RP). This study aims to validate and describe the frequency of HGB in a large cohort of Portuguese patients with RP.

METHODS

This single-centre, cross-sectional cohort study included consecutive patients with a genetic diagnosis of RP. SD-OCT images were reviewed to identify the presence of the HGB and other retinal comorbidities. The HGB was defined as a continuous hyperreflective band within the thickness of the ganglion cell layer (GCL). We built mixed-effects regression models, accounting for inter-eye correlations, to investigate features predictive of visual acuity. Subsequently, a reduced model was fitted.

RESULTS

A total of 398 eyes from 201 patients were included. HGB was identified in 69 (17.3%) eyes from 39 (19.4%) patients. Patients presenting with the HGB were significantly younger at diagnosis and at symptom onset. Median BCVA [ETDRS (IQR)] was 65 (29) letters in eyes with the HGB and 70 (21) letters in eyes without HGB (p < 0.001). In both the full and reduced mixed-effects models, the presence of HGB and macular hole (MH) was significantly associated with worse BCVA.

CONCLUSIONS

This study validates the recent description of HGB within the GCL in a subset of patients with RP. Eyes with HGB demonstrated significantly worse BCVA compared to those without HGB, suggesting that the presence of HGB may serve as an SD-OCT biomarker of worse visual prognosis in these patients.

Optical coherence tomography biomarkers in MYO7A-inherited retinal dystrophy: longitudinal study in pediatric patients

PURPOSE

This study aims to answer a key question: is MYO7A-inherited retinal dystrophy (MYO7A-IRD) a photoreceptor-first or retinal pigment epithelium-first disease? A second aim was to determine the most useful biomarkers to monitor disease progression in pediatric patients with Usher syndrome type 1B (USH1) secondary to MYO7A mutation.

METHODS

Fifty-two eyes from 26 patients with genetically-confirmed MYO7A-IRD underwent swept-source optical coherence tomography (SS-OCT). Structural abnormalities were evaluated and correlated with follow-up time and best corrected visual acuity (BCVA). All patients were evaluated at baseline and after ≥ 40 months of follow-up.

RESULTS

The mean (SD) patient age was 9.92 (± 4.1) years. Mean follow-up time was 43 (± 3.2) months. At the final evaluation, the most common qualitative abnormalities in the subfoveal area were alterations in the photoreceptor outer segments (76.9% of eyes) and in the interdigitation zone (IZ) (80.8%). The presence of cystoid macular edema at baseline was independently associated with worse BCVA at the final assessment (increase in LogMAR estimate = 0.142; t(45.00) = 2.78, p = 0.009). The mean width of the ellipsoid and interdigitation zones decreased significantly (by 668 μm and 278 μm, respectively; both p < 0.001).

CONCLUSION

This study shows that disruption of the photoreceptor outer segments and the IZ are the first alterations detected by SS-OCT in the early phases of MYO7A-IRD. These data highlight the potential value of measuring the width of the ellipsoid and IZ to evaluate disease progression. These findings also demonstrate the utility of monitoring for the emergence of cystic lesions as biomarkers of worse visual prognosis in patients with MYO7A-IRD.

Long-term natural history of ellipsoid zone width in USH2A-retinopathy

AIMS

To investigate the long-term natural history of ellipsoid zone (EZ) width in USH2A-retinopathy.

METHODS

EZ width measurements from optical coherence tomography were retrospectively obtained from 110 eyes of 55 participants with molecularly confirmed biallelic USH2A-retinopathy. We used a hierarchical Bayesian method to construct and compare different mathematical models describing the long-term decline of EZ width.

RESULTS

Compared with linear and quadratic models, exponential decline best represented the long-term loss of EZ width based on the deviance information criterion score. Log-transformed EZ width declined linearly over 30 years of inferred disease duration (median: 0.063 (IQR: 0.040-0.086) log (µm)/year). Compared with the raw EZ width decline rate, the log-transformed EZ width decline rate required 48% fewer patients to achieve an identically powered 1-year trial (38 vs 73 participants). Log EZ width decline rate was uncoupled from baseline EZ width (Spearman ρ=-0.18, p=0.06) and age (ρ=-0.10, p=0.31). Eyes with Usher syndrome exhibited earlier median onset ages of macular EZ width loss (18.8 (IQR: 13.1-24.7) vs 28.1 (IQR: 18.5-35.8) years, p<0.001) but comparable log EZ width decline rates (0.060 (IQR: 0.035-0.100) vs 0.065 (IQR: 0.050-0.079) log (µm)/year; p=0.42).

CONCLUSIONS

EZ width follows an exponential decline in USH2A-retinopathy. Compared with raw EZ width decline rate, log-transformed EZ width decline rate may be a superior endpoint for clinical trials. Syndromic eyes exhibit an earlier onset of macular EZ width loss but progress at comparable rates to non-syndromic eyes.

Navigating the Genetic Landscape: A Comprehensive Review of Novel Therapeutic Strategies for Retinitis Pigmentosa Management

Retinitis pigmentosa (RP) is a collection of retinal disorders characterized by the progressive degeneration of photoreceptor cells, leading to significant visual impairment and, in severe cases, blindness. RP affects individuals worldwide and can be inherited through various genetic patterns, making it a genetically diverse condition. Despite considerable advancements in diagnostic methods and supportive therapies, there is currently no cure for RP. The focus of existing management strategies is on slowing the progression of the disease and improving the quality of life for those affected. This comprehensive review explores the latest therapeutic approaches in the management of RP, highlighting advancements in genetic therapies, such as gene augmentation and editing, as well as cell-based treatments including stem cell transplantation and induced pluripotent stem cell (iPSC) technologies. Emerging methods like optogenetics and pharmacological interventions designed to preserve retinal function are also discussed. Additionally, the review examines technological innovations, including retinal prosthetics and the use of artificial intelligence, which hold the potential to revolutionize RP treatment. The challenges and limitations associated with these novel therapies, such as safety concerns, accessibility issues, and regulatory hurdles, are critically evaluated. By providing an overview of current research and future directions, this review aims to inform clinicians and researchers about the state of the art in RP treatment and the prospects for achieving significant therapeutic advancements.

Using Multimodal Imaging to Refine the Phenotype of PRPH2-associated Retinal Degeneration

OBJECTIVE

To refine retinal peripherin-2 (PRPH2)-associated retinal degeneration (PARD) phenotypes using multimodal imaging.

DESIGN

Retrospective review of clinical records and multimodal imaging.

SUBJECTS

Patients who visited the inherited retinal degeneration (IRD) clinic at 2 tertiary referral eye centers with molecularly confirmed IRD due to PRPH2 variants.

METHODS

Retinal imaging was reviewed using ultrawidefield (UWF) pseudocolor, UWF fundus autofluorescence, and spectral-domain OCT. Phenotypes were identified in the macular or peripheral region. A combined phenotype was considered if any phenotypes were present in both macular and peripheral regions. Mixed phenotypes in the macula or peripheral retina were considered if there were 2 distinct phenotypes identified in the same eye. The presence or absence of atrophy in the macular or peripheral area was also noted.

MAIN OUTCOME MEASURE

Grading of multimodal imaging by phenotype and atrophy.

RESULTS

A total of 144 eyes of 72 patients were included in this study. The majority of the eyes had combined macular and peripheral phenotypes (89/144, 61.8%), whereas 44 (30.6%) eyes had isolated macular findings, and 11 (7.6%) had isolated peripheral findings. Twenty-five eyes were classified with mixed macular phenotypes, whereas fundus flavimaculatus dystrophy type was the most common combined macular and peripheral phenotype (54/144, 37.5%): n = 10 with macular dystrophy and macular flavimaculatus dystrophy (MFD), and n = 15 with butterfly pattern dystrophy and MFD. Nearly half of the eyes (71/144, 49.3%) were identified to have concomitant outer retinal atrophy. Fundus flavimaculatus type dystrophy was also associated with the highest proportion of concomitant atrophy (57/71, 80.3%).

CONCLUSIONS

Peripherin-2-associated retinal degeneration demonstrates a wide array of phenotypes using multimodal imaging. We report that combinations of classically described phenotypes were often seen. Additionally, macular and peripheral atrophy were often associated with PARD phenotypes. Refinement of PARD phenotypes using newer multimodal imaging techniques will likely assist diagnosis and future clinical trials.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Current Status of Clinical Trials Design and Outcomes in Retinal Gene Therapy

With the rapid expansion of methods encompassed by the term gene therapy, new trials exploring the safety and efficacy of these methods are initiated more frequently. As a result, important questions arise pertaining the design of these trials and patient participation. One of the most important aspects of any clinical trial is the ability to measure the trial's outcome in a manner that will reflect the effect of the treatment and allow its quantification, whether the trial is aimed at preservation or restoration of retinal cells (photoreceptors and others), vision, or both. Here we will review the existing methods for quantification of trial outcomes, stressing the importance of assessing the participant's visual function and not just visual acuity. We will also describe the key considerations in trial design. Finally, as patient safety remains the primary concern in any trial participation, we will outline the key principles in that regard.

Segmentation and quantitative analysis of optical coherence tomography (OCT) images of laser burned skin based on deep learning

Evaluation of skin recovery is an important step in the treatment of burns. However, conventional methods only observe the surface of the skin and cannot quantify the injury volume. Optical coherence tomography (OCT) is a non-invasive, non-contact, real-time technique. Swept source OCT uses near infrared light and analyzes the intensity of light echo at different depths to generate images from optical interference signals. To quantify the dynamic recovery of skin burns over time, laser induced skin burns in mice were evaluated using deep learning of Swept source OCT images. A laser-induced mouse skin thermal injury model was established in thirty Kunming mice, and OCT images of normal and burned areas of mouse skin were acquired at day 0, day 1, day 3, day 7, and day 14 after laser irradiation. This resulted in 7000 normal and 1400 burn B-scan images which were divided into training, validation, and test sets at 8:1.5:0.5 ratio for the normal data and 8:1:1 for the burn data. Normal images were manually annotated, and the deep learning U-Net model (verified with PSPNe and HRNet models) was used to segment the skin into three layers: the dermal epidermal layer, subcutaneous fat layer, and muscle layer. For the burn images, the models were trained to segment just the damaged area. Three-dimensional reconstruction technology was then used to reconstruct the damaged tissue and calculate the damaged tissue volume. The average IoU value and f-score of the normal tissue layer U-Net segmentation model were 0.876 and 0.934 respectively. The IoU value of the burn area segmentation model reached 0.907 and f-score value reached 0.951. Compared with manual labeling, the U-Net model was faster with higher accuracy for skin stratification. OCT and U-Net segmentation can provide rapid and accurate analysis of tissue changes and clinical guidance in the treatment of burns.

Compensation of inner retina to early-stage photoreceptor degeneration in a RhoP23H/+ mouse model of retinitis pigmentosa

Retinitis pigmentosa (RP) is an inherited retinal disorder characterized by the degeneration of photoreceptors. RhoP23H/+ mice, which carry a Pro23His mutation in the RHODOPSIN (Rho) gene, are one of the most studied animal models for RP. However, except for the photoreceptors, other retinal neural cells have not been fully investigated in this model. Here, we record the temporal changes of the retina by optical coherence tomography (OCT) imaging of the RhoP23H/+ mice, from early to mid-phase of retinal degeneration. Based on thickness analysis, we identified a natural retinal thickness adaption in wild-type mice during early adulthood and observed morphological compensation of the inner retina layer to photoreceptor degeneration in the RhoP23H/+ mice, primarily on the inner nuclear layer (INL). RhoP23H/+ mice findings were further validated via: histology showing the negative correlation of INL and ONL thicknesses; as well as electroretinogram (ERG) showing an increased b-wave to a-wave ratio. These results unravel the sequential morphologic events in this model and suggest a better understanding of retinal degeneration of RP for future studies.

Recent advances in the use of optical coherence tomography in neuro-ophthalmology: A review

Optical coherence tomography (OCT) is an in vivo imaging modality that provides non-invasive, high resolution and fast cross-sectional images of the optic nerve head, retina and choroid. OCT angiography (OCTA) is an emerging tool. It is a non-invasive, dye-free imaging approach of visualising the microvasculature of the retina and choroid by employing motion contrast imaging for blood flow detection and is gradually receiving attention for its potential roles in various neuro-ophthalmic and retinal conditions. We will review the clinical utility of the OCT in the management of various common neuro-ophthalmic and neurological disorders. We also review some of the OCTA research findings in these conditions. Finally, we will discuss the limitations of OCT as well as introduce other emerging technologies.

New insights in the multimodal imaging of retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of inherited rod-cone dystrophies, noted for a high genotypical and phenotypical heterogeneity.Traditionally, VA, visual field, and electroretinography have been used to assess RP progression. However, visual acuity and visual field tests are essentially subjective and, especially in the late stages of the disease, are unable to confidently reveal minor progression. Therefore, there is a need for novel examination modalities that rely on quantitative, structural measurements. In this regard, several non-invasive imaging techniques have been studied, including spectral-domain optical coherence tomography, optical coherence tomography angiography, and fundus autofluorescence. By correlating surrogate biomarkers with functional measurements of the disease, these techniques may be able to develop reliable outcome meters that can be used to gain a deeper understanding of the underlying causes of the disease and to assess the effectiveness of therapy even before an actual loss of vision occurs.In this review, we will summarize the recent imaging findings and biomarkers that have been identified in RP patients. Our goal is to provide information that can promptly aid in selecting patients for clinical trials and new gene therapies, monitoring the disease progression, and evaluating treatment outcomes.

Clinical presentation and macular morphology in retinitis pigmentosa patients

Background

Optical coherence tomography (OCT) is a noninvasive, frequently used imaging technology that enables detailed viewing of retina anatomy. It is used to monitor disease progression in retinitis pigmentosa (RP) eyes, including detecting changes in retinal thickness.

Purpose

The purpose of the study is to determine the clinical presentation and macular morphology in RP eyes using OCT imaging.

Methods

A retrospective review of case records and OCT scans in eyes diagnosed with RP in two ophthalmic clinics in Nigeria. Biodata, Snellen best-corrected visual acuity (BCVA), intraocular pressure (IOP), vertical cup-to-disc ratio (VCDR), and presence of maculopathy were determined. Data were analyzed using IBM SPSS version 22.0 (IBM Corp. Armonk, NY, USA).

Results

Fifty-five eyes of 28 patients (18 males and 10 females), with a mean age of 47.16 ± 15.56 years (22-77 years), were studied. 40-49 years was the most frequent age group, 28.6%. Severe visual impairment occurred in 22% of eyes and myopia in 32%. Twenty-nine percent had undergone cataract surgery or had a significant cataract. The mean IOP was 11 mmHg, and the mean VCDR was 0.46. On OCT examination, macular atrophy was the most common finding in 74.5% of eyes, epiretinal membrane in 16.3%, cystoid macular edema in 7.3%, vitreomacular adhesion in 5.4%, and vitreomacular traction in 1.8%. There was no association between macular morphology, macular thickness, and BCVA (P = 0.155, P = 0.424).

Conclusion

OCT provides information on macula structure in RP eyes. About 14.5% of eyes had a normal macula, while 85.5% had a maculopathy, confirming that RP eyes have a higher rate of maculopathy than non RP eyes. OCT evaluation of an RP eye should be a standard workup for the early detection of such maculopathy and monitoring for disease progression.

Gene Therapy in Hereditary Retinal Dystrophies: The Usefulness of Diagnostic Tools in Candidate Patient Selections

PURPOSE

Gene therapy actually seems to have promising results in the treatment of Leber Congenital Amaurosis and some different inherited retinal diseases (IRDs); the primary goal of this strategy is to change gene defects with a wild-type gene without defects in a DNA sequence to achieve partial recovery of the photoreceptor function and, consequently, partially restore lost retinal functions. This approach led to the introduction of a new drug (voretigene neparvovec-rzyl) for replacement of the RPE65 gene in patients affected by Leber Congenital Amaurosis (LCA); however, the treatment results are inconstant and with variable long-lasting effects due to a lack of correctly evaluating the anatomical and functional conditions of residual photoreceptors. These variabilities may also be related to host immunoreactive reactions towards the Adenovirus-associated vector. A broad spectrum of retinal dystrophies frequently generates doubt as to whether the disease or the patient is a good candidate for a successful gene treatment, because, very often, different diseases share similar genetic characteristics, causing an inconstant genotype/phenotype correlation between clinical characteristics also within the same family. For example, mutations on the RPE65 gene cause Leber Congenital Amaurosis (LCA) but also some forms of Retinitis Pigmentosa (RP), Bardet Biedl Syndrome (BBS), Congenital Stationary Night Blindness (CSNB) and Usher syndrome (USH), with a very wide spectrum of clinical manifestations. These confusing elements are due to the different pathways in which the product protein (retinoid isomer-hydrolase) is involved and, consequently, the overlapping metabolism in retinal function. Considering this point and the cost of the drug (over USD one hundred thousand), it would be mandatory to follow guidelines or algorithms to assess the best-fitting disease and candidate patients to maximize the output. Unfortunately, at the moment, there are no suggestions regarding who to treat with gene therapy. Moreover, gene therapy might be helpful in other forms of inherited retinal dystrophies, with more frequent incidence of the disease and better functional conditions (actually, gene therapy is proposed only for patients with poor vision, considering possible side effects due to the treatment procedures), in which this approach leads to better function and, hopefully, visual restoration. But, in this view, who might be a disease candidate or patient to undergo gene therapy, in relationship to the onset of clinical trials for several different forms of IRD? Further, what is the gold standard for tests able to correctly select the patient? Our work aims to evaluate clinical considerations on instrumental morphofunctional tests to assess candidate subjects for treatment and correlate them with clinical and genetic defect analysis that, often, is not correspondent. We try to define which parameters are an essential and indispensable part of the clinical rationale to select patients with IRDs for gene therapy. This review will describe a series of models used to characterize retinal morphology and function from tests, such as optical coherence tomography (OCT) and electrophysiological evaluation (ERG), and its evaluation as a primary outcome in clinical trials. A secondary aim is to propose an ancillary clinical classification of IRDs and their accessibility based on gene therapy's current state of the art.

MATERIAL AND METHODS

OCT, ERG, and visual field examinations were performed in different forms of IRDs, classified based on clinical and retinal conditions; compared to the gene defect classification, we utilized a diagnostic algorithm for the clinical classification based on morphofunctional information of the retina of patients, which could significantly improve diagnostic accuracy and, consequently, help the ophthalmologist to make a correct diagnosis to achieve optimal clinical results. These considerations are very helpful in selecting IRD patients who might respond to gene therapy with possible therapeutic success and filter out those in which treatment has a lower chance or no chance of positive results due to bad retinal conditions, avoiding time-consuming patient management with unsatisfactory results.

Thicknesses of the retina and choroid in children with retinitis pigmentosa

PURPOSE

To compare the retinal thicknesses (RT) and choroidal thicknesses (CT) in retinitis pigmentosa (RP) children with those of healthy children using enhanced depth imaging (EDI) optical coherence tomography (OCT). The RT and CT in different genetic subgroups of autosomal dominant RP (ADRP) and X-linked inheritance RP (XLRP) were further studied to investigate the characteristics of retinal and choroidal changes in the early stages of RP.

METHOD

A retrospective analysis was performed on a group of patients with RP who underwent EDI-OCT. Thirty-two children (64 eyes) with RP and 28 age- and refraction-matched healthy children (56 eyes) were included in the study. Seven of the 32 RP children (14 eyes) had X-linked inheritance RP, and 10 (20 eyes) had autosomal dominant inheritance RP. RT and CT were measured by optical coherence tomography and compared between the 32 children with RP and 28 controls and between 7 XLRP and 10 ADRP children.

RESULT

Among the 32 children with RP, there were 18 males and 14 females with an average age of 6.6 ± 2.4 years. The mean RT was smaller in the RP group than in the control group at all of the locations. The mean temporal CT was smaller in the RP group (243.76 ± 60.82 μm) than in the control group (275.23 ± 40.92 μm) (P = 0.001), while there was no significant thinning on the foveal or nasal side. The best-corrected visual acuity of the XLRP group (0.40 ± 0.19) was worse than that of the ADRP group (0.68 ± 0.21) (P = 0.001), but the disease duration was the same (P = 0.685). The mean foveal RT was smaller in the XLRP group (173.85 ± 22.87 μm) than in the ADRP group (192.20 ± 9.70 μm) (P = 0.003), while there was no significant thinning at the other locations we studied. The mean temporal CT was smaller in the XLRP group (211.21 ± 69.41 μm) than in the ADRP group (274.45 ± 57.91 μm) (P = 0.007); CT measurements in XLRP children showed a more severe reduction on the temporal side.

CONCLUSION

The choroid in RP children was preferentially smaller on the temporal side of the macula, and retinal thinning was relatively extensive. Children with RP have strong clinical and genetic heterogeneity. The XLRP children demonstrated greater RT reduction at the fovea and greater CT reduction at the temporal side of the macula than the ADRP children. Our findings also provide evidence that the changes in thicknesses may be indicative of the greater severity of XLRP versus ADRP in the early stage.

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.