Comparison between Widefield En Face Swept-Source OCT and Conventional Multimodal Imaging for the Detection of Reticular Pseudodrusen

Rediscovering Age-Related Macular Degeneration with Swept-Source OCT Imaging: The 2022 Charles L. Schepens, MD, Lecture

PURPOSE

Swept-source OCT angiography (SS-OCTA) scans of eyes with age-related macular degeneration (AMD) were used to replace color, autofluorescence, infrared reflectance, and dye-based fundus angiographic imaging for the diagnosis and staging of AMD. Through the use of different algorithms with the SS-OCTA scans, both structural and angiographic information can be viewed and assessed using both cross sectional and en face imaging strategies.

DESIGN

Presented at the 2022 Charles L. Schepens, MD, Lecture at the American Academy of Ophthalmology Retina Subspecialty Day, Chicago, Illinois, on September 30, 2022.

PARTICIPANTS

Patients with AMD.

METHODS

Review of published literature and ongoing clinical research using SS-OCTA imaging in AMD.

MAIN OUTCOME MEASURES

Swept-source OCT angiography imaging of AMD at different stages of disease progression.

RESULTS

Volumetric SS-OCTA dense raster scans were used to diagnose and stage both exudative and nonexudative AMD. In eyes with nonexudative AMD, a single SS-OCTA scan was used to detect and measure structural features in the macula such as the area and volume of both typical soft drusen and calcified drusen, the presence and location of hyperreflective foci, the presence of reticular pseudodrusen, also known as subretinal drusenoid deposits, the thickness of the outer retinal layer, the presence and thickness of basal laminar deposits, the presence and area of persistent choroidal hypertransmission defects, and the presence of treatment-naïve nonexudative macular neovascularization. In eyes with exudative AMD, the same SS-OCTA scan pattern was used to detect and measure the presence of macular fluid, the presence and type of macular neovascularization, and the response of exudation to treatment with vascular endothelial growth factor inhibitors. In addition, the same scan pattern was used to quantitate choriocapillaris (CC) perfusion, CC thickness, choroidal thickness, and the vascularity of the choroid.

CONCLUSIONS

Compared with using several different instruments to perform multimodal imaging, a single SS-OCTA scan provides a convenient, comfortable, and comprehensive approach for obtaining qualitative and quantitative anatomic and angiographic information to monitor the onset, progression, and response to therapies in both nonexudative and exudative AMD.

FINANCIAL DISCLOSURE(S)

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

En Face Optical Coherence Tomography Illustrates the Trizonal Distribution of Drusen and Subretinal Drusenoid Deposits in the Macula

PURPOSE

To analyze the topographic distribution of macular drusen and subretinal drusenoid deposits (SDDs) using single-capture en face spectral domain optical coherence tomography (SD-OCT) imaging.

DESIGN

Retrospective case series.

METHODS

Analysis of 33 eyes of 20 patients with evidence of SDDs. Structural en face OCT images were reconstructed using a 40-µm-thick slab positioned from 48 to 88 µm above the Bruch membrane. The Early Treatment of Diabetic Retinopathy Study (ETDRS) grid and a rod/cone density map were overlaid on the en face OCT images, and the distribution of different subtypes of SDDs and macular drusen were assessed.

RESULTS

A total of 31 eyes (94%) showed a trizonal distribution pattern of drusen and SDDs. Whereas small to large drusen tended to aggregate in the central circle, dot SDDs predominated in the inner ring and the inner portion of the outer ring of the ETDRS grid and ribbon SDDs localized to the outer ring and outside the ETDRS grid. Of note, drusen colocalized to the region of greatest cone density, whereas ribbon SDDs colocalized to the area of greatest rod density. The dot SDDs mapped to the intermediate region with mixed rod and cone representation.

CONCLUSION

Dot and ribbon subtypes of SDDs and macular drusen show a characteristic trizonal distribution. The locations of these lesions colocalize according to the different densities of the cones and rods in the retina and may reflect varying pathophysiological activities of these photoreceptor subtypes.

Stargardt's pigmentosa: A novel combination of two inherited retinal dystrophies

60-year-old woman referring visual disability. She presented bone spicule pigmentation and retinal atrophy in all peripheral retina, as well as macular retinal flecks. Multimodal imaging showed typical findings of both inherited retinal dystrophies (IRD). Electroretinogram confirmed rod dysfunction. Biallelic mutations were found in ABCA4 and CNGA1 genes. Although not common, different IRDs may be present in a same patient at the same time. This is the first reported case of the combination of RP with late-onset Stargardt's disease. We propose the name 'Stargardt's pigmentosa' for this novel clinical entity.

Advances in swept-source optical coherence tomography and optical coherence tomography angiography

Background

The fast development of swept-source optical coherence tomography (SS-OCT) and swept-source optical coherence tomography angiography (SS-OCTA) enables both anterior and posterior imaging of the eye. These techniques have evolved from a research tool to an essential clinical imaging modality.

Main text

The longer wavelength and faster speed of SS-OCT and SS-OCTA facilitate better visualization of structure and vasculature below pigmented tissue with a larger field of view of the posterior segment and 360-degree visualization of the anterior segment. In the past 10 years, algorithms dealing with OCT and OCTA data also vastly improved the image quality and enabled the automated quantification of OCT- and OCTA-derived metrics. This technology has enriched our current understanding of healthy and diseased eyes. Even though the high cost of the systems currently limited the widespread use of SS-OCT and SS-OCTA at the first beginning, the gap between research and clinic practice got obviously shortened in the past few years.

Conclusions

SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift toward more widespread adoption of new imaging technology in clinical practice.

Optometrists' attitudes toward using OCT angiography lag behind other retinal imaging types

PURPOSE

While optometrists' attitudes toward established retinal imaging types are generally positive, they are unknown for optical coherence tomography angiography (OCTA). We performed a cross-sectional survey to estimate attitudes toward OCTA and identify clinician and/or practice characteristics that influence them.

METHODS

A paper-based survey was mailed to 252 randomly selected optometrists in Australia. Five-point Likert-scale items from a previous survey assessing attitudes toward new technology were included to probe respondent characteristics and attitudes toward retinal imaging. Performance expectancy attitudes toward OCTA were elicited by the statement 'I believe OCTA is useful in daily practice'. Mean scores out of five (mean [SD]) were rounded and mapped to appropriate descriptive statements.

RESULTS

The response rate was 47% (118/252). The mean (SD) age of respondents was 44.0 (13.8) years and 50.8% (60/118) were female. Optometrists had 19.9 (14.0) years of clinical experience and 66.9% (79/118) worked at independent practices. In total, 8.5% (10/118) of respondents used OCTA to provide clinical care. Optometrists agreed that optical coherence tomography (OCT), colour fundus imaging, ultra-wide field imaging and fundus autofluorescence (mean scores 3.6-4.7 out of 5) were useful in daily practice but felt neutral about whether OCTA was useful (3.4 [0.8]). Optometrists believed that OCTA was less enjoyable to use (p < 0.0001), less endorsed by peers (p < 0.0001) and felt less confident that they had the knowledge to interpret OCTA (p < 0.0001) compared to other retinal imaging types.

CONCLUSIONS

Optometrists are undecided on whether OCTA is useful in daily practice and had lower expectations that using OCTA would confer job performance benefits compared to other retinal imaging types. Further work is needed to advocate the benefits of using OCTA across the profession.

Decreased Macular Choriocapillaris Perfusion in Eyes With Macular Reticular Pseudodrusen Imaged With Swept-Source OCT Angiography

Purpose

To determine if macular reticular pseudodrusen (RPD) were associated with markers of impaired macular choroidal perfusion, we investigated measurements of macular choriocapillaris (CC) flow deficits (FDs), CC thickness, and mean choroidal thickness (MCT) in eyes with macular RPD compared with normal eyes and eyes with soft drusen.

Methods

Eyes with intermediate age-related macular degeneration (iAMD) and normal eyes underwent 6 × 6 mm swept-source optical coherence tomography angiography (SS-OCTA) imaging to diagnose macular RPD, occupying over 25% of the fovea-centered 5 mm diameter circle, and measure outer retinal layer (ORL) thickness, CC FDs, CC thickness, MCT, and choroidal vascularity index (CVI) using previously published strategies within the same fovea-centered 5 mm circle.

Results

Ninety eyes were included; 30 normal eyes, 30 eyes with soft drusen, and 30 eyes with macular RPD. The RPD eyes showed higher macular CC FDs than normal eyes (P < 0.001) and soft drusen eyes (P = 0.019). Macular CC thickness was decreased in RPD eyes compared with normal eyes (P < 0.001) and soft drusen eyes (P = 0.016). Macular MCT in RPD eyes was thinner than normal eyes (P = 0.005) and soft drusen eyes (P < 0.001). No statistically and clinically significant differences were found in the ORL thickness and CVI measurements between RPD eyes and the other two groups (all P > 0.05).

Conclusions

Eyes with macular RPD had decreased macular CC perfusion, decreased CC thickness, and decreased MCT measurements compared with normal and soft drusen eyes, suggesting that RPD may result from impaired choroidal perfusion.

Reticular pseudodrusen: A critical phenotype in age-related macular degeneration

Reticular pseudodrusen (RPD), or subretinal drusenoid deposits (SDD), refer to distinct lesions that occur in the subretinal space. Over the past three decades, their presence in association with age-related macular degeneration (AMD) has become increasingly recognized, especially as RPD have become more easily distinguished with newer clinical imaging modalities. There is also an increasing appreciation that RPD appear to be a critical AMD phenotype, where understanding their pathogenesis will provide further insights into the processes driving vision loss in AMD. However, key barriers to understanding the current evidence related to the independent impact of RPD include the heterogeneity in defining their presence, and failure to account for the confounding impact of the concurrent presence and severity of AMD pathology. This review thus critically discusses the current evidence on the prevalence and clinical significance of RPD and proposes a clinical imaging definition of RPD that will help move the field forward in gathering further key knowledge about this critical phenotype. It also proposes a putative mechanism for RPD formation and how they may drive progression to vision loss in AMD, through examining current evidence and presenting novel findings from preclinical and clinical studies.

Correlations Between Choriocapillaris and Choroidal Measurements and the Growth of Geographic Atrophy Using Swept Source OCT Imaging

PURPOSE

Correlations among enlargement rates (ERs) of geographic atrophy (GA) and choriocapillaris (CC) flow deficits (FDs), mean choroidal thickness (MCT), and choroidal vascularity index (CVI) were investigated using swept source-optical coherence tomography (SS-OCT) in age-related macular degeneration (AMD).

DESIGN

A retrospective review of prospective, observational case series.

METHODS

Eyes with GA from AMD were imaged with SS-OCT using 6 × 6-mm scan pattern. GA lesions were identified and measured using customized en face structural images, and annual square root ERs of GA were calculated. At baseline, choriocapillaris FDs from different regions outside the GA were measured, and MCT and CVI from the entire scan area were measured. All measurements were performed using previously published and validated algorithms.

RESULTS

A total of 38 eyes from 27 patients were included. The CC FDs within each region around GA lesions were highly correlated with ERs of GA (all P < .005). CVI inside the GA region was correlated with the ERs (P = .03), whereas other choroidal measurements had no significant correlation with the ERs of GA (P > .06).

CONCLUSIONS

Statistically significant correlations were found between the ERs of GA and CC percentage of FD (FD%) from the entire scan region outside the GA and not just the region immediately adjacent to the GA. These results suggest that abnormal CC perfusion throughout the macula contributes to disease progression in eyes with GA. CVI inside the GA region could also be a potential indicator for the growth of GA.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Posterior vitreous detachment in patients with diabetes mellitus

PURPOSE

To compare the progression of posterior vitreous detachment (PVD) during aging among eyes of diabetics with diabetic retinopathy (DR), eyes of diabetics without DR, and eyes of nondiabetics.

STUDY DESIGN

Prospective cross-sectional study.

METHODS

One-hundred thirty-three diabetic eyes with DR (DR group), 254 diabetic eyes without DR (non-DR group), and 577 nondiabetic eyes (nondiabetic group) were divided into four age categories: 1) 40-49 years, 2) 50-59 years, 3) 60-69 years, and 4) 70-79 years. The PVD state was examined using swept source-optical coherence tomography and classified into five stages: 0 (non PVD), 1 (paramacular PVD), 2 (perifoveal PVD), 3 (vitreofoveal separation), and 4 (complete PVD).

RESULTS

The PVD stage significantly progressed in the DR, non-DR, and nondiabetic groups (p <0.0001). At 40-49 and 50-59 years, the PVD stage did not differ significantly among the three groups. At 60-69 and 70-79 years, the PVD stage was significantly less progressed in the DR than the non-DR and nondiabetic groups (p ≤0.0027), and did not differ significantly between the non-DR and nondiabetic groups. At 70-79 years, complete PVD was detected in 40.6% of eyes in the DR group, 69.6% in the non-DR group, and 73.5% of eyes in the nondiabetic group.

CONCLUSION

PVD progresses later in diabetic eyes with DR than in diabetic eyes without DR and nondiabetics eyes at 60 and 70 years of age, suggesting a stronger vitreomacular adhesion in diabetics with DR.

Correlations between Choriocapillaris Flow Deficits around Geographic Atrophy and Enlargement Rates Based on Swept-Source OCT Imaging

PURPOSE

To determine the possible correlation between the annual enlargement rates (ERs) of geographic atrophy (GA) with the percentage and size of the choriocapillaris (CC) flow deficits (FDs) surrounding GA, measured with swept-source OCT angiography (SS-OCTA) images.

DESIGN

Prospective, observational case series.

PARTICIPANTS

Patients with GA secondary to nonexudative AMD.

METHODS

Patients were imaged with a 100-kHz SS-OCTA instrument (PLEX Elite 9000, Carl Zeiss Meditec, Dublin, CA) using a 6×6-mm field of view scan pattern. The GA area measurements were obtained from en face SS-OCT sub-retinal pigment epithelium (RPE) slab images. Visualization of the CC and quantification of FDs were performed using a previously published validated algorithm based on a 20-μm thickness slab with the inner boundary located beneath Bruch's membrane. The percentage of CC FDs (FD%) and the average FD area measurements were calculated in different regions around the GA.

MAIN OUTCOME MEASURES

The correlation between the CC FDs and the ERs of GA.

RESULTS

Twenty-two eyes from 15 patients were eligible for the analysis. The annual square root ERs for GA ranged from 0.07 to 0.75 mm/year. The CC FD% and average FD area measurements were highly correlated with each other (P < 0.001), with the highest FD values found in the region closest to the margin of GA. The ERs correlated best with the average CC FD area measurements in the total scan area minus the area of GA (Pearson r = 0.747; P < 0.001) than those in the regions immediately surrounding the GA (r = 0.544; P = 0.009).

CONCLUSIONS

Contrary to expectations, the global CC FD measurements had a better correlation with the ERs of GA than those in the regions immediately around the GA. The most likely explanation for this outcome is that normal age-related increases in FDs within the central macula confound the correlations between the ERs of GA and FDs, whereas the regions furthest away from the margins of GA are less affected by normal age-related changes and reflect FD alterations related to AMD severity.

Sex-Related Differences in the Progression of Posterior Vitreous Detachment with Age

PURPOSE

To compare the difference in the progression of posterior vitreous detachment (PVD) between men and women in relation to age.

DESIGN

Observational cross-sectional study.

PARTICIPANTS

One hundred eyes of 100 male patients and 100 eyes of 100 female patients in 4 age groups: 40 to 49 years of age, 50 to 59 years of age, 60 to 69 years of age, and 70 years of age or older.

METHODS

Using swept-source (SS) OCT, PVD was classified into 5 stages: 0, no PVD; 1, paramacular PVD; 2, perifoveal PVD; 3, vitreofoveal separation; and 4, complete PVD. The PVD stage distribution was compared between men and women in the 4 age groups and among the age groups.

MAIN OUTCOME MEASURES

Stage of PVD determined using SS OCT.

RESULTS

In both male and female eyes, the stage of PVD progressed significantly in association with the age group (P < 0.0001). The distribution of the PVD stage did not differ significantly between men and women in the 40- to 49- and the 50- to 59-year age groups. The distribution of the PVD stage was significantly more progressed in women than in men, however, in those 60 to 69 years of age and those 70 years of age and older (P ≤ 0.0292). At 40 to 49 years of age, no PVD (stage 0) and paramacular PVD (stage 1) were detected in 92 (92.0%) female eyes and 93 (93.0%) male eyes. At 70 years of age or older, vitreofoveal separation (stage 3) and complete PVD (stage 4) were detected in 93 (93.0%) female eyes and 78 (78.0%) male eyes.

CONCLUSIONS

Posterior vitreous detachment significantly progresses with age in both genders, specifically between 40 years of age and 70 years of age or older. Posterior vitreous detachment progression occurs significantly faster in female eyes than in male eyes at 60 years of age or older, suggesting that the macular pathologic features associated with PVD occur at a younger age in women.

Peripheral Changes Associated With Delayed Dark Adaptation in Age-related Macular Degeneration

PURPOSE

To study the association between peripheral changes in age-related macular degeneration (AMD) and dark adaptation (DA).

DESIGN

Prospective, cross-sectional study.

METHODS

We recruited patients with AMD and a control group (>50 years) without any vitreoretinal disease. Ultra-widefield (UWF) pseudocolor and fundus autofluorescence (FAF) were obtained, and were assessed by 2 graders for the presence of several peripheral changes in perimacular, midperipheral, and far-peripheral zones. All participants were also imaged with 7-field color fundus photographs used for AMD staging (Age-Related Eye Disease Study classification system). Both eyes of study participants were tested with a dark adaptation (DA) extended protocol (20 minutes). Multilevel mixed-effect models (accounting for correlated outcomes between 2 eyes) were used for analyses.

RESULTS

We included 128 eyes (n = 72 patients), 75% with AMD and the remainder controls. The presence of reticular pigmentary changes in the midperipheral (ß = 4.3, P = .012) and far-peripheral zones (ß = 8.4, P < .001) was associated with delayed rod-intercept times (RITs), even after adjusting for confounding factors. The presence, number, and extent of peripheral classic drusen did not show a similar association (P ≥ .148). The presence of a mottled decreased FAF pattern in the midperipheral zone was also associated with prolonged RITs (β = 4.4, P = .031).

CONCLUSION

Our results suggest an association between DA and the presence of peripheral reticular pigmentary changes, as well as the presence of a peripheral mottled decreased FAF pattern. This provides new insights on the clinical significance of peripheral changes in AMD, and their contribution to impairments on DA.

Subretinal drusenoid deposits AKA pseudodrusen

A distinction between conventional drusen and pseudodrusen was first made in 1990, and more recently knowledge of pseudodrusen, more accurately called subretinal drusenoid deposits (SDDs), has expanded. Pseudodrusen have a bluish-white appearance by biomicroscopy and color fundus photography. Using optical coherence tomography, pseudodrusen were found to be accumulations of material internal to the retinal pigment epithelium that could extend internally through the ellipsoid zone. These deposits are more commonly seen in older eyes with thinner choroids. Histologic evaluation of these deposits revealed aggregations of material in the subretinal space between photoreceptors and retinal pigment epithelium. SDDs contain some proteins in common with soft drusen but differ in lipid composition. Many studies reported that SDDs are strong independent risk factors for late age-related macular degeneration. Geographic atrophy and type 3 neovascularization are particularly associated with SDD. Unlike conventional drusen, eyes with SDD show slow dark adaptation and poor contrast sensitivity. Outer retinal atrophy develops in eyes with regression of SDD, a newly recognized form of late age-related macular degeneration. Advances in imaging technology have enabled many insights into this condition, including associated photoreceptor, retinal pigment epithelium, and underlying choroidal changes.

Automated drusen detection in dry age-related macular degeneration by multiple-depth, en face optical coherence tomography

We introduce a method to automatically detect drusen in dry age-related macular degeneration (AMD) from optical coherence tomography with minimum need for layer segmentation. The method is based on the en face detection of drusen areas in C-scans at certain distances above the Bruch's membrane, circumventing the difficult task of pathologic retinal pigment epithelium segmentation. All types of drusen can be detected, including the challenging subretinal drusenoid deposits (pseudodrusen). The high sensitivity and accuracy demonstrated here shows its potential for detection of drusen onset in early AMD.

Spotlight on reticular pseudodrusen

Age-related macular degeneration (AMD) is a leading cause of vision loss in patients >50 years old. The hallmark of the disease is represented by the accumulation of extracellular material between retinal pigment epithelium and the inner collagenous layer of Bruch's membrane, called drusen. Although identified almost 30 years ago, reticular pseudodrusen (RPD) have been recently recognized as a distinctive phenotype. Unlike drusen, they are located in the subretinal space. RPD are strongly associated with late AMD, especially geographic atrophy, type 2 and 3 choroidal neovascularization, which, in turn, are less common in typical AMD. RPD identification is not straightforward at fundus examination, and their identification should employ at least 2 different imaging modalities. In this narrative review, we embrace all aspects of RPD, including history, epidemiology, histology, imaging, functional test, natural history and therapy.

Evaluation of coronary artery disease as a risk factor for reticular pseudodrusen

PURPOSE

Reticular pseudodrusen (RPD) are a risk factor for late age-related macular degeneration (AMD). Associations between RPD and coronary artery disease (CAD) have been reported from small case-control studies. This study investigated the association of RPD within a predominantly CAD cohort.

METHODS

A subgroup of subjects from a multicentre randomised controlled trial of CT coronary angiography (CTCA) underwent ultrawide field (UWF) retinal imaging CAD determined by CTCA and was categorised as normal, non-obstructive or obstructive. Specific AMD features in UWF images were graded. Standardised grids were used to record the spatial location of AMD features, including RPD. Multivariate confounder adjusted regression models assessed the association between RPD and CAD.

RESULTS

The 534 participants were aged 27-75 years (mean 58±9 years; 425 (80%) ≥50 years) with a male preponderance (56%). Within the study sample, 178 (33%) had no CAD, 351 (66%) had CAD. RPD was detected in 30 participants (5.6%) and bilaterally in 23. Most participants with bilateral RPD had intermediate AMD 17 (74%). After adjustment for potential confounders (age, sex, drusen >125 µm, smoking status), multivariate analysis found no significant association between CAD and RPD (OR 1.31; 95% CI (0.57 to 3.01); p=0.52). A significant association was identified between RPD and intermediate AMD (OR 3.18; 95% CI (1.61 to 6.27); p=0.001).

CONCLUSION

We found no evidence to support an association between CAD and RPD. RPD was strongly associated with intermediate AMD features.

TRIAL REGISTRATION NUMBER

NCT01149590, Post results.