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

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.

The Clinical Findings, Pathogenic Variants, and Gene Therapy Qualifications Found in a Leber Congenital Amaurosis Phenotypic Spectrum Patient Cohort

This retrospective study examines the clinical characteristics and underlying genetic variants that exist in a Leber congenital amaurosis (LCA) patient cohort evaluated at the inherited retinal disease (IRD) clinic at the University of Minnesota (UMN)/M Health System. Our LCA cohort consisted of 33 non-syndromic patients and one patient with Joubert syndrome. We report their relevant history, clinical findings, and genetic testing results. We monitored disease presentation utilizing ocular coherence tomography (OCT) and fundus autofluorescence (FAF). Electroretinogram testing (ERG) was performed in patients when clinically indicated. Next-generation sequencing (NGS) and genetic counseling was offered to all evaluated patients. Advanced photoreceptor loss was noted in 85.7% of the subjects. All patients who underwent FAF had findings of either a ring of macular hypo/hyper AF or peripheral hypo-AF. All patients had abnormal ERG findings. A diagnostic genetic test result was identified in 74.2% of the patients via NGS single-gene testing or panel testing. Two patients in our cohort qualified for Luxturna® and both received treatment at the time of this study. These data will help IRD specialists to understand the genetic variants and clinical presentations that characterize our patient population in the Midwest region of the United States.

Uveitis masquerade syndromes: An approach to diagnosis

Uveitis masquerade syndromes are a diverse group of clinical entities which mimic conventional immune-mediated uveitis due to the presence of inflammatory signs but are resistant to anti-inflammatory therapy. Misdiagnosis hinders appropriate management in these conditions and may result in poor outcomes. This review discusses commonly encountered neoplastic and non-neoplastic disease processes that masquerade as intraocular inflammation with a focus on relevant clinical features and adjunctive investigations that are helpful in reaching a correct diagnosis.

Fundus autofluorescence in uveitis: from pathogenesis to imaging interpretation

PURPOSE

This review aims to summarize the current fundus autofluorescence (FAF) ailment for diagnosis and follow-up of uveitis.

METHODS

A thorough literature search was performed in the PubMed database.

RESULTS

FAF maps the retinal pigment epithelium's (RPE) health. Therefore, several posterior infectious and non. This fast, easy-to-perform, noninvasive technique can detect and manage infectious uveitis.

CONCLUSIONS

FAF serves to understand pathophysiologic mechanisms of uveitis and is a valuable prognostic indicator of themselves.

Time-domain full-field optical coherence tomography (TD-FF-OCT) in ophthalmic imaging

Ocular imaging plays an irreplaceable role in the evaluation of eye diseases. Developing cellular-resolution ophthalmic imaging technique for more accurate and effective diagnosis and pathogenesis analysis of ocular diseases is a hot topic in the cross-cutting areas of ophthalmology and imaging. Currently, ocular imaging with traditional optical coherence tomography (OCT) is limited in lateral resolution and thus can hardly resolve cellular structures. Conventional OCT technology obtains ultra-high resolution at the expense of a certain imaging range and cannot achieve full field of view imaging. In the early years, Time-domain full-field OCT (TD-FF-OCT) has been mainly used for ex vivo ophthalmic tissue studies, limited by the low speed and low full-well capacity of existing two-dimensional (2D) cameras. The recent improvements in system design opened new imaging possibilities for in vivo applications thanks to its distinctive optical properties of TD-FF-OCT such as a spatial resolution almost insensitive to aberrations, and the possibility to control the curvature of the optical slice. This review also attempts to look at the future directions of TD-FF-OCT evolution, for example, the potential transfer of the functional-imaging dynamic TD-FF-OCT from the ex vivo into in vivo use and its expected benefit in basic and clinical ophthalmic research. Through non-invasive, wide-field, and cellular-resolution imaging, TD-FF-OCT has great potential to be the next-generation imaging modality to improve our understanding of human eye physiology and pathology.

New technology using crystalline lens autofluorescence for presbyopia and cataract grading

PURPOSE

To investigate  whether fundus autofluorescence (FAF) obtained using an ultra-wide field (UWF) fundus camera with an artificial opacity pattern can grade the degree of presbyopia and nuclear cataract.

METHODS

Sixty eyes of 30 patients were enrolled in this prospective diagnostic study. The nuclear cataract (nuclear color/opalescence (NC/NO)) was graded according to the Lens Opacity Classification System III. The monocular near point of accommodation (NPA) was measured in eyes with NC3/NO3 or less. The mean gray value difference between the central 8 artificial opacity lesions and peripheral 8 artificial opacity lesions in the retinal AF was measured. The correlation between the mean gray value difference, NPA, and nuclear cataract grade was analyzed.

RESULTS

The mean nuclear cataract grade of 60 eyes was 3.2 ± 1.6 and mean NPA of 37 eyes was 45.3 ± 16.1 cm. The mean gray value differences increased with increasing nuclear cataract grade (eyes with NC/NO grade 1, 53.3 ± 11.4; 2, 78.3 ± 13.6; 3, 95.2 ± 12.2; 4, 101.6 ± 11.9; 5, 109.0 ± 22.9; and 6, 121.1 ± 12.0; p < 0.001). The mean gray value difference was positively correlated with both the monocular NPA (R² = 0.637; β coefficient = 1.009; 95% CI, 0.748 to 1.271; p < 0.001) and nuclear cataract grade (R² = 0.661; β coefficient = 12.437; 95% CI, 10.097 to 14.778; p < 0.001).

CONCLUSIONS

The FAF camera with an artificial opacity pattern attached can be used to effectively diagnose the degree of presbyopia and nuclear cataract.

Ultra-Widefield Fluorescein Angiography Image Brightness Compensation Based on Geometrical Features

Ultra-widefield fluorescein angiography (UWFA) is an emerging imaging modality used to characterise pathologies in the retinal vasculature, such as microaneurysms (MAs) and vascular leakages. Despite its potential value for diagnosis and disease screening, objective quantitative assessment of retinal pathologies by UWFA is currently limited because laborious manual processing is required. In this report, we describe a geometrical method for uneven brightness compensation inherent to UWFA imaging technique. The correction function is based on the geometrical eyeball shape, therefore it is fully automated and depends only on pixel distance from the center of the imaged retina. The method's performance was assessed on a database containing 256 UWFA images with the use of several image quality measures that show the correction method improves image quality. The method is also compared to the commonly used CLAHE approach and was also employed in a pilot study for vascular segmentation, giving a noticeable improvement in segmentation results. Therefore, the method can be used as an image preprocessing step in retinal UWFA image analysis.

An In Silica Model for RPE Loss Patterns in Choroideremia

Purpose

To use empirical data to develop a model of cell loss in choroideremia that predicts the known exponential rate of RPE loss and central, scalloped preservation pattern seen in this disease.

Methods

A computational model of RPE loss was created in Python 3.7, which constructed an array of RPE cells clusters, binarized as either live or atrophic. Two rules were applied to this model: the background effect gave each cell a chance of dying defined by a background function, and the neighbor effect increased the chance of RPE cell death if a neighbor were dead. The known anatomic distribution of rods, RPE, choriocapillaris density, amacrine, ganglion, and cone cells were derived from the literature and applied to this model. Atrophy growth rates were measured over arbitrary time units and fit to the known exponential decay model. The main outcome measures: included topography of atrophy over time and fit of simulated residual RPE area to exponential decay.

Results

A background effect alone can simulate exponential decay, but does not simulate the central island preservation seen in choroideremia. An additive neighbor effect alone does not simulate exponential decay. When the neighbor effect multiplies the background effect using the rod density function, our model follows an exponential decay, similar to previous observations. Also, our model predicts a residual island of RPE that resembles the topographic distribution of residual RPE seen in choroideremia.

Conclusions

The pattern of RPE loss in choroideremia can be predicted by applying simple rules. The RPE preservation pattern typically seen in choroideremia may be related to the underlying pattern of rod density. Further studies are needed to validate these findings.

Stargardt disease masquerades

PURPOSE OF REVIEW

Stargardt disease is the most common inherited macular dystrophy but has a wide clinical spectrum, and several inherited macular dystrophies have phenotypic similarities that can make clinical diagnosis challenging. This review seeks to highlight key clinical and multimodal imaging features to aid clinicians in accurate diagnosis.

RECENT FINDINGS

Multimodal imaging has provided additional information to aid in the diagnosis of Stargardt disease and its masquerades. These data from multimodal imaging are important to correlate with findings from clinical examination to help support the clinical diagnosis or guide molecular investigations.

SUMMARY

This review highlights the key similarities and differences, in history, clinical examination and multimodal imaging, to help distinguish between Stargardt disease and other macular dystrophies. These findings can help direct a focused molecular analysis for accurate diagnosis, which is critical in the era of gene and stem cell therapies.

Clinical Characteristics, Differential Diagnosis and Genetic Analysis of Concentric Retinitis Pigmentosa

Concentric retinitis pigmentosa (RP), in which retinal degeneration is limited in the periphery, is rare and little information exists to date on the subject. Herein, we describe the clinical and genetic characteristics of this atypical form of RP. We retrospectively reviewed our database and identified 14 patients with concentric RP. Additionally, 14 patients with age-matched typical RP were also included. Patients with concentric RP had better visual acuity (logarithm of minimum angle of resolution −0.04 vs. 0.32, p = 0.047) and preserved ellipsoid zones (7630 µm vs. 2646 µm, p < 0.001) compared to typical RP. The electroretinogram showed subnormal but recordable responses in patients with concentric RP. Genetic testing was done in nine patients with concentric RP and revealed causative mutations in the EYS gene in one patient and the RP9 gene in one patient. Two patients had myotonic dystrophy and the diagnosis was revised as myotonic dystrophy-associated retinopathy. Concentric RP is a rare, atypical form of RP with better visual function. There is some overlap in the causative genes in concentric and typical RP. Myotonic dystrophy-associated retinopathy is an important differential diagnosis.

Correlation between fundus autofluorescence and visual function in patients with cone-rod dystrophy

This study aimed to investigate the relationship between autofluorescence (AF) signal measured with ultra-wide field imaging and visual functions in patients with cone-rod dystrophy (CORD). A retrospective chart review was performed for CORD patients. We performed the visual field test and fundus autofluorescence (FAF) measurement and visualized retinal structures with optical coherence tomography (OCT) on the same day. Using binarised FAF images, we identified a low FAF area ratio (LFAR: low FAF/30°). Relationships between age and logMAR visual acuity (VA), central retinal thickness (CRT), central choroidal thickness (CCT), mean deviation (MD) value, and LFAR were investigated. Thirty-seven eyes of 21 CORD patients (8 men and 13 women) were enrolled. The mean patient age was 49.8 years. LogMAR VA and MD were 0.52 ± 0.47 and − 17.91 ± 10.59 dB, respectively. There was a significant relationship between logMAR VA and MD (p = 0.001). LogMAR VA significantly correlated with CRT (p = 0.006) but not with other parameters. Conversely, univariate analysis suggested a significant relationship between MD and LFAR (p = 0.001). In the multivariate analysis, LFAR was significantly associated with MD (p = 0.002). In conclusion, it is useful to measure the low FAF area in patients with CORD. The AF measurement reflects the visual field deterioration but not VA in CORD.

The role of multimodal imaging and vision function testing in ABCA4-related retinopathies and their relevance to future therapeutic interventions

The aim of this review article is to describe the specific features of Stargardt disease and ABCA4 retinopathies (ABCA4R) using multimodal imaging and functional testing and to highlight their relevance to potential therapeutic interventions. Standardised measures of tissue loss, tissue function and rate of change over time using formal structured deep phenotyping in Stargardt disease and ABCA4R are key in diagnosis, and prognosis as well as when selecting cohorts for therapeutic intervention. In addition, a meticulous documentation of natural history will be invaluable in the future to compare treated with untreated retinas. Despite the familiarity with the term Stargardt disease, this eponymous classification alone is unhelpful when evaluating ABCA4R, as the ABCA4 gene is associated with a number of phenotypes, and a range of severity. Multimodal imaging, psychophysical and electrophysiologic measurements are necessary in diagnosing and characterising these differing retinopathies. A wide range of retinal dystrophy phenotypes are seen in association with ABCA4 mutations. In this article, these will be referred to as ABCA4R. These different phenotypes and the existence of phenocopies present a significant challenge to the clinician. Careful phenotypic characterisation coupled with the genotype enables the clinician to provide an accurate diagnosis, associated inheritance pattern and information regarding prognosis and management. This is particularly relevant now for recruiting to therapeutic trials, and in the future when therapies become available. The importance of accurate genotype-phenotype correlation studies cannot be overemphasised. This approach together with segregation studies can be vital in the identification of causal mutations when variants in more than one gene are being considered as possible. In this article, we give an overview of the current imaging, psychophysical and electrophysiological investigations, as well as current therapeutic research trials for retinopathies associated with the ABCA4 gene.

Comparison of two ultra-widefield imaging for detecting peripheral retinal breaks requiring treatment

AIM

To compare the sensitivity of Optomap Panoramic 200 and Clarus 500 in detecting peripheral retinal breaks that required treatment.

METHODS

This prospective study enrolled consecutive patients undergoing laser for treatment-requiring peripheral retinal breaks from May 2019 to July 2019. The patients first underwent indirect ophthalmoscopy examination with scleral indentation by a retinal consultant and then ultra-widefield imaging by a single trained technician on Optomap 200 and Clarus 500 in all nine ocular gazes. The images were analysed by two independent investigators to look for the number and location of the breaks. The sensitivity of each platform was calculated as the number of treatment-requiring breaks identified by the system divided by the number of breaks identified on clinical examination.

RESULTS

Clinical examination of 49 eyes (41 patients) showed 116 treatment-requiring breaks. Overall sensitivity for identifying such breaks for Optomap and Clarus was 80.2% (n = 93) and 74.1% (n = 86) respectively (p = 0.274). The sensitivities in superior (p = 0.665), temporal (p = 0.146) and inferior (p = 0.889) quadrants were statistically similar for both the platforms. The sensitivity of Optomap was slightly higher than Clarus in emmetropic (p = 0.046) and phakic (p = 0.061) eyes, but similar in myopic (p = 0.448) and pseudophakic (p = 0.191) eyes.

CONCLUSION

The ability to detect treatment-requiring retinal breaks is similar for both Optomap and Clarus systems.