Quantifying the Separation Between the Retinal Pigment Epithelium and Bruch's Membrane using Optical Coherence Tomography in Patients with Inherited Macular Degeneration

Extensive macular atrophy with pseudodrusen-like appearance (EMAP) clinical characteristics, diagnostic criteria, and insights from allied inherited retinal diseases and age-related macular degeneration

Extensive macular atrophy with pseudodrusen-like appearance (EMAP) was first described in France in 2009 as a symmetric and rapidly progressive form of macular atrophy primarily affecting middle-aged individuals. Despite the recent identification of a significant number of cases in Italy and worldwide, EMAP remains an underrecognized condition. The clinical triad typical of EMAP consists of vertically oriented macular atrophy with multilobular borders, pseudodrusen-like deposits across the posterior pole and mid-periphery, and peripheral pavingstone degeneration. Nonetheless, recent research has portrayed EMAP as a highly stage-dependent condition, allowing the identification of novel disease hallmarks, including a diffuse separation between the Bruch's membrane and the retinal pigment epithelium, along with consistent sparing of a region temporal to the macula. Additionally, retinal electrophysiology is particularly useful in distinguishing EMAP from age-related macular degeneration (AMD). Supported by unpublished data from the largest EMAP cohorts worldwide, this review aims to provide a comprehensive and updated description of EMAP, now recognized as a severely blinding disease characterized by diffuse chorioretinal atrophy and photoreceptor dysfunction. Furthermore, we propose a set of diagnostic criteria that incorporate clinical, imaging, and functional tests, to facilitate the recognition of this clinical entity. Lastly, we aim to shed light on its pathogenesis by comparing it with AMD and monogenic retinal disorders exhibiting similar phenotypes.

Polarization-resolved analysis of outer retinal bands: investigating ballistic and multiply scattered photons using full-field swept-source optical coherence tomography

Precise interpretation of the anatomical origins of outer retinal optical coherence tomography (OCT) presents technical challenges owing to the delicate nature of the retina. To address this challenge, our study introduces a novel polarization-sensitive full-field swept-source OCT (FF-SS-OCT) that provides parallel-polarization and cross-polarization OCT measurements, predominantly capturing ballistically reflected photons and multiply scattered photons, respectively. Notably, parallel-polarization OCT unveils layer-like structures more effectively, including the inner plexiform layer (IPL) sub-layers, outer plexiform layer (OPL) sub-layers (in rod-dominant regions), and rod/cone outer segment (OS) tips, compared to cross-polarization OCT, where such sub-layers are not visible. Through a comparative analysis of parallel-polarization and cross-polarization OCT images of the outer retina, we discovered that the 2nd outer retinal OCT band results from contributions from both the ellipsoid zone (EZ) and the inner segment/outer segment (IS/OS) junction. Similarly, the 3rd outer retinal OCT band appears to reflect contributions from both the interdigitation zone (IZ) and photoreceptor OS tips. This polarization-sensitive approach advances our understanding of the origins of outer retinal OCT signals and proposes potential new biomarkers for assessing retinal health and diseases.

Phenotyping and genotyping inherited retinal diseases: Molecular genetics, clinical and imaging features, and therapeutics of macular dystrophies, cone and cone-rod dystrophies, rod-cone dystrophies, Leber congenital amaurosis, and cone dysfunction syndromes

Inherited retinal diseases (IRD) are a leading cause of blindness in the working age population and in children. The scope of this review is to familiarise clinicians and scientists with the current landscape of molecular genetics, clinical phenotype, retinal imaging and therapeutic prospects/completed trials in IRD. Herein we present in a comprehensive and concise manner: (i) macular dystrophies (Stargardt disease (ABCA4), X-linked retinoschisis (RS1), Best disease (BEST1), PRPH2-associated pattern dystrophy, Sorsby fundus dystrophy (TIMP3), and autosomal dominant drusen (EFEMP1)), (ii) cone and cone-rod dystrophies (GUCA1A, PRPH2, ABCA4, KCNV2 and RPGR), (iii) predominant rod or rod-cone dystrophies (retinitis pigmentosa, enhanced S-Cone syndrome (NR2E3), Bietti crystalline corneoretinal dystrophy (CYP4V2)), (iv) Leber congenital amaurosis/early-onset severe retinal dystrophy (GUCY2D, CEP290, CRB1, RDH12, RPE65, TULP1, AIPL1 and NMNAT1), (v) cone dysfunction syndromes (achromatopsia (CNGA3, CNGB3, PDE6C, PDE6H, GNAT2, ATF6), X-linked cone dysfunction with myopia and dichromacy (Bornholm Eye disease; OPN1LW/OPN1MW array), oligocone trichromacy, and blue-cone monochromatism (OPN1LW/OPN1MW array)). Whilst we use the aforementioned classical phenotypic groupings, a key feature of IRD is that it is characterised by tremendous heterogeneity and variable expressivity, with several of the above genes associated with a range of phenotypes.

Optical Coherence Tomography in Inherited Macular Dystrophies: A Review

Macular dystrophies (MDs) constitute a collection of hereditary retina disorders leading to notable visual impairment, primarily due to progressive macular atrophy. These conditions are distinguished by bilateral and relatively symmetrical abnormalities in the macula that significantly impair central visual function. Recent strides in fundus imaging, especially optical coherence tomography (OCT), have enhanced our comprehension and diagnostic capabilities for MD. OCT enables the identification of neurosensory retinal disorganization patterns and the extent of damage to retinal pigment epithelium (RPE) and photoreceptor cells in the dystrophies before visible macular pathology appears on fundus examinations. It not only helps us in diagnostic retinal and choroidal pathologies but also guides us in monitoring the progression of, staging of, and response to treatment. In this review, we summarize the key findings on OCT in some of the most common MD.

Macular neovascularization in inherited retinal diseases: A review

Inherited retinal diseases (IRDs) are the most common cause of blindness in working-age adults. Macular neovascularization (MNV) may be a presenting feature or occurs as a late-stage complication in several IRDs. We performed an extensive literature review on MNV associated with IRDs. MNV is a well-known complication of Sorsby fundus dystrophy and pseudoxanthoma elasticum. Those with late-onset Stargardt disease may masquerade as exudative age-related macular degeneration (AMD) when MNV is the presenting feature. Peripherinopathies may develop MNV that responds well to a short course of anti-vascular endothelial growth factor (anti-VEGF) therapy, while bestrophinopathies tend to develop MNV in the early stages of the disease without vision loss. Enhanced S-cone syndrome manifests type 3 MNV that typically regresses into a subfoveal fibrotic nodule. MNV is only a rare complication in choroideraemia and rod-cone dystrophies. Most IRD-related MNVs exhibit a favorable visual prognosis requiring less intensive regimens of anti-vascular endothelial growth factor therapy compared to age-related macular degeneration. We discuss the role of key imaging modalities in the diagnosis of MNV across a wide spectrum of IRDs and highlight the gaps in our knowledge with respect to the natural history and prognosis to pave the way for future directions of research.

Treatment Strategy With Gene Editing for Late-Onset Retinal Degeneration Caused by a Founder Variant in C1QTNF5

Purpose

Genome editing is an emerging group of technologies with the potential to ameliorate dominant, monogenic human diseases such as late-onset retinal degeneration (L-ORD). The goal of this study was to identify disease stages and retinal locations optimal for evaluating the efficacy of a future genome editing trial.

Methods

Twenty five L-ORD patients (age range, 33-77 years; median age, 59 years) harboring the founder variant S163R in C1QTNF5 were enrolled from three centers in the United Kingdom and United States. Patients were examined with widefield optical coherence tomography (OCT) and chromatic perimetry under dark-adapted and light-adapted conditions to derive phenomaps of retinal disease. Results were analyzed with a model of a shared natural history of a single delayed exponential across all subjects and all retinal locations.

Results

Critical age for the initiation of photoreceptor loss ranged from 48 years at the temporal paramacular retina to 74 years at the inferior midperipheral retina. Subretinal deposits (sRET-Ds) became more prevalent as critical age was approached. Subretinal pigment epithelial deposits (sRPE-Ds) were detectable in the youngest patients showing no other structural or functional abnormalities at the retina. The sRPE-D thickness continuously increased, reaching 25 µm in the extrafoveal retina and 19 µm in the fovea at critical age. Loss of light sensitivity preceded shortening of outer segments and loss of photoreceptors by more than a decade.

Conclusions

Retinal regions providing an ideal treatment window exist across all severity stages of L-ORD.

Longitudinal Changes of Retinal Structure in Molecularly Confirmed C1QTNF5 Patients With Late-Onset Retinal Degeneration

Purpose

The purpose of this study was to present our findings on the natural history of late-onset retinal degeneration (LORD) in patients with molecularly confirmed C1QTNF5 heterozygous pathogenic variants and assess suitability of retinal structure parameters for disease monitoring.

Methods

Sixteen patients with C1QTNF5-LORD were retrospectively identified from Moorfields Eye Hospital, UK. Fundus autofluorescence (FAF), optical coherence tomography (OCT) scans, and best-corrected visual acuity (BCVA) were collected. Area of atrophy (AA) was manually drawn in FAF images. Ellipsoid zone (EZ) width and foveal retinal thickness of the whole retina and outer retina were extracted from OCT scans. Age-related changes were tested with linear-mixed models.

Results

Patients had median age of 62.3 years (interquartile range [IQR] = 58.8-65.4 years) at baseline, and median follow-up of 5.1 years (IQR = 2.6-7.6 years). AA, EZ width, and retinal thickness parameters remained unchanged until age 50 years, but showed significant change with age thereafter (all P < 0.0001). AA and EZ width progressed rapidly (dynamic range normalized rates = 4.3-4.5%/year) from age 53.9 and 50.8 years (estimated inflection points), respectively. Retinal thickness parameters showed slower progression rates (range = 1.6-2.5%/year) from age 60 to 62.3. BCVA (median = 0.3 LogMAR, IQR = 0.0-1.0 at baseline) showed a rapid decline (3.3%) from age 70 years. Findings from patients with earlier disease showed FAF atrophy manifests in the temporal retina initially, and then progresses nasally.

Conclusions

Patients with LORD remained asymptomatic until age 50 years, before suffering rapid outer retinal degeneration. EZ width and AA showed rapid progression and high interocular correlation, representing promising outcome metrics. Clinical measures also capturing the temporal retina may be preferable, enabling earlier detection and better disease monitoring.

Translational Relevance

Area of atrophy in FAF images and OCT-measured EZ width represent promising outcome metrics for disease monitoring in patients with C1QTNF5-LORD.

Outer retinal corrugations in late-onset retinal degeneration: a diagnostic finding demonstrated with multimodal imaging

OBJECTIVE

Late-onset retinal degeneration (L-ORD) is a rare autosomal dominant retinal degeneration that presents in the sixth decade and leads to severe visual loss. The objective of this paper is to describe outer retinal corrugations as a diagnostic feature of L-ORD.

METHODS

This retrospective study reviewed consecutive patients diagnosed with L-ORD, confirmed through complete ophthalmic examination, multimodal imaging and genetic tests. Multimodal imaging investigations included spectral domain-optical coherence tomography (SD-OCT) and ultra-wide-field colour and autofluorescence fundus photographs.

RESULTS

A total of 13 eyes of 9 patients with L-ORD had outer retinal corrugations identified on OCT scans.

CONCLUSION

Outer retinal corrugations may be a diagnostic finding for L-ORD. The detection of this sign may aid diagnosis and characterisation of this disease and help in the differential diagnosis with other acquired pathologies.

Bruch's Membrane: A Key Consideration with Complement-Based Therapies for Age-Related Macular Degeneration

The complement system is crucial for immune surveillance, providing the body's first line of defence against pathogens. However, an imbalance in its regulators can lead to inappropriate overactivation, resulting in diseases such as age-related macular degeneration (AMD), a leading cause of irreversible blindness globally affecting around 200 million people. Complement activation in AMD is believed to begin in the choriocapillaris, but it also plays a critical role in the subretinal and retinal pigment epithelium (RPE) spaces. Bruch's membrane (BrM) acts as a barrier between the retina/RPE and choroid, hindering complement protein diffusion. This impediment increases with age and AMD, leading to compartmentalisation of complement activation. In this review, we comprehensively examine the structure and function of BrM, including its age-related changes visible through in vivo imaging, and the consequences of complement dysfunction on AMD pathogenesis. We also explore the potential and limitations of various delivery routes (systemic, intravitreal, subretinal, and suprachoroidal) for safe and effective delivery of conventional and gene therapy-based complement inhibitors to treat AMD. Further research is needed to understand the diffusion of complement proteins across BrM and optimise therapeutic delivery to the retina.

NATURAL COURSE AND CLASSIFICATION OF EXTENSIVE MACULAR ATROPHY WITH PSEUDODRUSEN-LIKE APPEARANCE

PURPOSE

To describe the imaging characteristics and topographic expansion of retinal pigment epithelium (RPE) and outer retinal atrophy in extensive macular atrophy with pseudodrusen-like appearance.

METHODS

Three-year, prospective, observational study. Nine patients with extensive macular atrophy with pseudodrusen-like appearance (17 eyes; 6 women) with no other ocular conditions were annually examined; one eye was excluded because of macular neovascularization. Best-corrected visual acuity measurement, fundus photographs, blue-light autofluorescence, and optical coherence tomography were performed at each visit. Formation of atrophy was analyzed on optical coherence tomography at foveal and extrafoveal areas following the Classification of Atrophy Meeting recommendations. Spatial enlargement throughout four sectors was assessed on blue-light autofluorescence after placing an Early Treatment for Diabetic Retinopathy Study grid centered on the foveola.

RESULTS

Mean age was 53.0 ± 2.1 years at baseline with a follow-up of 36.6 ± 0.7 months. Thinning of the outer nuclear layer and disruption of the ellipsoid zone initially appeared above areas of RPE-Bruch membrane separation and preceded RPE atrophy. Subfoveal fibrosis was seen in 65% of the eyes. Superior sector involvement was found in all patients at baseline and was significantly larger than the other sectors at any time point ( P < 0.001). Best-corrected visual acuity declined from 68.0 ± 15.7 letters to 44.8 ± 14.9 letters during the follow-up and was significantly associated with subfoveal atrophy ( P < 0.001) and fibrosis ( P = 0.02).

CONCLUSION

Our findings suggest that primary alterations in patients with extensive macular atrophy with pseudodrusen-like appearance are present at the outer segment-RPE interface, with the superior Early Treatment for Diabetic Retinopathy Study sector being the most vulnerable, which progresses to extensive atrophy of the RPE and outer retinal layers. Accordingly, we propose a three-stage disease classification.

Choriocapillaris Flow Signal Impairment in Patients With Pseudoxanthoma Elasticum

Purpose

To quantify choriocapillaris flow alterations in patients with pseudoxanthoma elasticum (PXE) in pre-atrophic stages and its association with structural changes of the choroid and outer retina.

Methods

Thirty-two eyes of 21 patients with PXE and 35 healthy eyes of 35 controls were included. The density of choriocapillaris flow signal deficits (FDs) was quantified on 6 × 6-mm optical coherence tomography angiography (OCTA) images. Spectral-domain optical coherence tomography (SD-OCT) images were analyzed for thicknesses of the choroid and outer retinal microstructure and correlated with choriocapillaris FDs in the respective Early Treatment Diabetic Retinopathy Study subfield.

Results

The multivariable mixed model analysis for choriocapillaris FDs revealed significantly higher FDs associated with the group (PXE patients vs. controls +13.6; 95% confidence interval [CI] 9.87-17.3; P < 0.001), with increasing age (+0.22% per year; 95% CI 0.12-0.33; P < 0.001), and with retinal location (significantly higher FDs in nasal compared to temporal subfields). Choroidal thickness (CT) did not differ significantly between both groups (P = 0.078). The CT and choriocapillaris FDs were inversely correlated (-1.92 µm per %FDs; interquartile range -2.81 to -1.03; P < 0.001). Larger values of the choriocapillaris FDs were associated with significant thinning of the overlying photoreceptor layers (outer segments: -0.21 µm per %FDs, P < 0.001; inner segments: -0.12 µm per %FDs, P = 0.001; outer nuclear layer: -0.72 µm per %FDs; P < 0.001).

Conclusions

Patients with PXE display significant alterations of the choriocapillaris on OCTA even in pre-atrophic stages and in the absence of significant choroidal thinning. The analysis favors choriocapillaris FDs over choroidal thickness as a potential early outcome measure for future interventional trials in PXE. Further, increased FDs in nasal compared to temporal locations mirror the centrifugal spread of Bruch's membrane calcification in PXE.

Late-Onset Retinal Degeneration: Clinical Perspectives

Late-onset retinal degeneration (L-ORD) is a type of retinal dystrophy marked by nyctalopia and subretinal pigment epithelium deposits, which eventually promote retinal atrophy with final visual compromise. L-ORD may also present with changes in the anterior segment, notably long anterior zonules and iris atrophy, distinguishing it from other inherited eye conditions. Although it can clinically simulate age-related macular degeneration, L-ORD has a different course of progression and prognosis, requiring adequate diagnosis for patient counseling. This review summarizes the main clinical, genetic, pathophysiological, diagnostic, and therapeutic aspects of L-ORD to help ophthalmologists identify and manage this rare ocular disease.

Visual Dysfunction and Structural Correlates in Sorsby Fundus Dystrophy

PURPOSE

To elucidate morphological determinants of rod and cone dysfunction in Sorsby fundus dystrophy (SFD), and to systematically compare visual function tests for interventional trials.

DESIGN

Prospective cross-sectional study.

METHODS

Patients with SFD (n = 16) and controls (n = 20) underwent visual function testing (best-corrected visual acuity [BCVA] and low luminance visual acuity [LLVA], contrast sensitivity, mesopic and dark-adapted (DA) fundus-controlled perimetry [FCP], rod-mediated dark adaptation [RMDA]), and multimodal imaging. Vision-related quality of life was evaluated. FCP and RMDA thresholds were analyzed using mixed models and structure-function correlation using machine learning (ML). Longitudinal data of 1 patient with high-dose vitamin A supplementation were available.

RESULTS

Although photopic BCVA was normative in SFD, LLVA was impaired (0.30 LogMAR [0.20; 0.45] vs 0.20 LogMAR [0.03; 0.28], P < .05). Scotopic visual function exhibited a delayed rod-intercept time (21 minutes [12.15; 21] vs 4.05 minutes [3.22; 5.36], P < .001), and marked DA cyan mean sensitivity loss (-11.80 dB [-3.47; -19.85]), paralleled by a reduced vision-related quality of life. ML-based structure-function correlation allowed prediction of mesopic, DA cyan, and red sensitivity with high accuracy (cross-validated mean absolute error: 4.36, 7.77, and 5.31 dB, respectively), whereas RMDA could be slowed even in the absence of fundus alterations on multimodal imaging. After high-dose vitamin A supplementation, RMDA and DA thresholds improved markedly.

CONCLUSIONS

Patients with SFD exhibit severely impaired scotopic visual function even in the absence of funduscopic alterations on multimodal imaging. In contrast to BCVA, scotopic visual function tests are suitable to quantify dysfunction in the early stages. Improvement of scotopic dysfunction after (off-label) high-dose vitamin A intake, as observed in one patient in our study, is compatible with the hypothesized local deficiency of vitamin A secondary to Bruch's membrane alterations.

Reticular Pseudodrusen in Late-Onset Retinal Degeneration

PURPOSE

To characterize the association of reticular pseudodrusen (RPD) with late-onset retinal degeneration (L-ORD) using multimodal imaging.

DESIGN

Prospective, 2-center, longitudinal case series.

PARTICIPANTS

Twenty-nine patients with L-ORD.

METHODS

All patients were evaluated within a 3-year interval with near-infrared reflectance, fundus autofluorescence, and spectral-domain OCT. In addition, a subset of patients also underwent indocyanine green angiography, fundus fluorescein angiography, mesopic microperimetry, and multifocal electroretinography.

MAIN OUTCOME MEASURES

Prevalence, topographic distribution, and temporal phenotypic changes of RPD in L-ORD.

RESULTS

A total of 29 patients with molecularly confirmed L-ORD were included in this prospective study. Reticular pseudodrusen was detected in 18 patients (62%) at baseline, 10 of whom were men. The prevalence of RPD varied with age. The mean age of RPD patients was 57.3 ± 7.2 years. Reticular pseudodrusen was not seen in patients younger than the fifth decade of life (n = 3 patients) or in the eighth decade of life (n = 5 patients). Reticular pseudodrusen were found commonly in the macula with relative sparing of the fovea and also were identified in the peripheral retina. The morphologic features of RPD changed with follow-up. Two patients (3 eyes) demonstrated RPD regression.

CONCLUSIONS

Reticular pseudodrusen is found frequently in patients with L-ORD and at a younger age than in individuals with age-related macular degeneration (AMD). Reticular pseudodrusen exhibits quick formation and collapse, change in type and morphologic features with time, and relative foveal sparing and also has a peripheral retinal location in L-ORD.

Visible Light Optical Coherence Tomography (OCT) Quantifies Subcellular Contributions to Outer Retinal Band 4

Purpose

To use visible light optical coherence tomography (OCT) to investigate subcellular reflectivity contributions to the outermost (4th) of the retinal hyperreflective bands visualized by current clinical near-infrared (NIR) OCT.

Methods

Visible light OCT, with 1.0 µm axial resolution, was performed in 28 eyes of 19 human subjects (21-57 years old) without history of ocular pathology. Two foveal and three extrafoveal hyperreflective zones were consistently depicted within band 4 in all eyes. The two outermost hyperreflective bands, occasionally visualized by NIR OCT, were presumed to be the retinal pigment epithelium (RPE) and Bruch's membrane (BM). RPE thickness, BM thickness, and RPE interior reflectivity were quantified topographically across the macula.

Results

A method for correcting RPE multiple scattering tails was found to both improve the Gaussian goodness-of-fit for the BM intensity profile and reduce the coefficient of variation of BM thickness in vivo. No major topographical differences in macular BM thickness were noted. RPE thickness decreased with increasing eccentricity. Visible light OCT signal intensity in the RPE was weighted to the apical side and attenuated more across the RPE in the fovea than peripherally.

Conclusions

Morphometry of the presumed RPE and BM bands is consistent with known anatomy. Weighting of RPE reflectivity toward the apical side suggests that melanosomes are the predominant contributors to RPE backscattering and signal attenuation in young eyes.

Translational Relevance

By enabling morphometric analysis of the RPE and BM, visible light OCT deciphers the main reflectivity contributions to outer retinal band 4, commonly visualized by commercial OCT systems.

Autosomal Dominant Gyrate Atrophy-Like Choroidal Dystrophy Revisited: 45 Years Follow-Up and Association with a Novel C1QTNF5 Missense Variant

We present a long-term follow-up in autosomal dominant gyrate atrophy-like choroidal dystrophy (adGALCD) and propose a possible genotype/phenotype correlation. Ophthalmic examination of six patients from two families revealed confluent areas of choroidal atrophy resembling gyrate atrophy, starting in the second decade of life. Progression continued centrally, reaching the fovea at about 60 years of age. Subretinal deposits, retinal pigmentation or choroidal neovascularization as seen in late-onset retinal degeneration (LORD) were not observed. Whole genome sequencing revealed a novel missense variant in the C1QTNF5 gene (p.(Q180E)) which was found in heterozygous state in all affected subjects. Haplotype analysis showed that this variant found in both families is identical by descent. Three-dimensional modeling of the possible supramolecular assemblies of C1QTNF5 revealed that the p.(Q180E) variant led to the destabilization of protein tertiary and quaternary structures, affecting both the stability of the single protomer and the entire globular head, thus exerting detrimental effects on the formation of C1QTNF5 trimeric globular domains and their interaction. In conclusion, we propose that the p.(Q180E) variant causes a specific phenotype, adGALCD, that differs in multiple clinical aspects from LORD. Disruption of optimal cell-adhesion mechanisms is expected when analyzing the effects of the point mutation at the protein level.