Sensitivity and Specificity of Multimodal Imaging in Characterizing Drusen

Retromode Imaging Technology for Detecting Drusen-Like Deposits in Healthy Adults

PURPOSE

To investigate the ability of retromode imaging technology to visualize drusen-like deposits (DLDs) in the macular region of healthy individuals without retinal diseases. Additionally, the correlation between subject age and the density of DLDs was assessed and their topographic distribution was evaluated.

DESIGN

Prospective, observational, cross-sectional study SUBJECTS: Healthy volunteers (aged ≥ 35 years) without macular diseases.

METHODS

This study evaluated macular images in healthy adults using color fundus photography (FP) and retromode imaging. Two masked graders counted the number of DLDs identifiable with each modality. The standardized ETDRS concentric rings were adopted to divide DLDs based on their topographic distribution.

MAIN OUTCOME MEASURES

Comparison of the number of DLDs detected with each imaging modality. The association between DLDs and age. The topographic distribution of macular DLDs with retromode imaging.

RESULTS

The study included 91 eyes of 52 healthy volunteers (mean ± standard deviation age, 57.9 ± 10.9 years; range, 36-82 years). Overall, at least 1 DLD was present in 63.74% of eyes on color FP and 96.71% on retromode. Retromode imaging allowed detection of significantly more DLDs compared with color FP within the ETDRS grid (median [interquartile range], 4 [1-14] vs. 0 [0-0] respectively; P < 0.001). The density of DLDs was higher in the outer and inner rings compared with the central subfield (relative risk [RR], 16.70; 95% confidence interval [CI], 10.3-27.3 vs. RR 17.1; 95% CI, 10.5-27.6, respectively). Age was significantly correlated with DLDs density in all 3 sectors (all P < 0.05).

CONCLUSIONS

Retromode technology allowed the detection of a significantly higher number of DLDs compared with FP in the macula of healthy individuals. This noninvasive imaging modality could be used to investigate the effect of the aging process on the macula, fostering a better understanding of the pathophysiology of age-related macular diseases.

FINANCIAL DISCLOSURE(S)

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

Retromode imaging in retinal diseases: A systematic review of the literature

Retromode scanning laser ophthalmoscopy imaging captures a pseudo-3-dimensional image of the ocular fundus. Retromode scanning laser ophthalmoscopy imaging was introduced first in 2008 using the Nidek F-10 scanning laser ophthalmoscope (F-10; Nidek Co., Gamagori, Japan). At that time, no major role was described for this imaging modality. The interest in retromode scanning laser ophthalmoscopy imaging is reemerging with the recent advent of the Mirante that combines scanning laser ophthalmoscopy and optical coherence tomography (Nidek Co., Gamagori, Japan) that can capture retromode images of the fundus. We summarize the findings and clinical implications of retromode imaging using the Nidek F-10 and the Mirante in retinal diseases with the aim of helping researchers direct their future studies.

Retromode Imaging in Age-Related Macular Degeneration

Background and Objectives: Retromode is a relatively new retinal-imaging technique that is based on the transillumination principle and is obtained with a scanning laser ophthalmoscope that uses light in the infrared spectrum. The laser light penetrates into the deep retinal layers and the choroid. Retromode images are captured with a laterally displaced aperture, and the detector captures only the scattered light. The result is a high-contrast pseudo-three-dimensional image. Age-related macular degeneration (AMD) is a disabling retinal disease. AMD is characterized in its early stage by small and intermediate drusen formation, while the signs of intermediate AMD are large drusen and/or pigmentary abnormalities. Late AMD has two forms, geographic atrophy, which is the advanced form of dry AMD, and wet AMD. Most of the lesions of AMD are located in the outer layers of the retina. This new imaging method can provide a glimpse of the deep retinal layers' topographic changes in a non-invasive, fast, and effective way that can match the other imaging tools available. Materials and Methods: The literature review was performed by searching the PubMed database using the following combination of keywords: retromode imaging and age-related macular degeneration. Relevant images similar to the ones in the literature were identified and used as models. Results: The purpose of this article is to highlight the utility of incorporating retromode imaging into the multimodal evaluation of the retina in patients with AMD and to gather and integrate these findings into a brief but comprehensive paper. Conclusions: Retromode imaging is a good screening, diagnosis, and monitoring tool for patients with AMD.

Enhanced Detection of Reticular Pseudodrusen on Color Fundus Photos by Image Embossing

PURPOSE

To evaluate whether processing a color fundus photo (CFP) using an image embossing technique can improve the detection of reticular pseudodrusen (RPD).

METHODS

This post-hoc analysis included the eyes of subjects enrolled in the Amish Eye Study with early or intermediate age-related macular degeneration and evidence of RPD. All patients underwent CFP, near-infrared reflectance (NIR), and fundus autofluorescence (FAF) imaging. The ground-truth presence of RPD was established with a combination of NIR and FAF imaging. An embossing processed (EP) image was created by replacing each pixel of the CFP image with a highlight or a shadow representing light and dark boundaries in the original CFP image. The presence of RPD in CFP and EP images was assessed by two graders in a masked fashion and the sensitivity of CFP and EP for detection of RPD was evaluated. Cohen's kappa (k) was used to test inter-grader agreement for CFP and EP.

RESULTS

A total of 106 eyes from 62 patients with RPDs were analyzed. The sensitivity for detection of RPD on CFP and EP was 63.2% (95%CI: 52.0%-74.4%) and 91.5% (95%CI: 85.0%-98.0%), respectively. The inter-rater reliabilities of CFP and EP for RPD detection were 0.81 and 0.84, respectively.

CONCLUSIONS

Embossing of CFP can improve the sensitivity for detection of RPD. The embossing technique can be a useful tool for better assessment of the true frequency of RPD in datasets where only CFP images are available.

Scanning laser ophthalmoscopy retroillumination: applications and illusions

Scanning laser ophthalmoscopes (SLOs) are used widely for reflectance, fluorescence or autofluorescence photography and less commonly for retroillumination imaging. SLOs scan a visible light or near-infrared radiation laser beam across the retina, collecting light from each retinal spot as it’s illuminated. An SLO’s clinical applications, image contrast and axial resolution are largely determined by an aperture overlying its photodetector. High contrast, reflectance images are produced using small diameter, centered apertures (confocal apertures) that collect retroreflections and reject side-scattered veiling light returned from the fundus. Retroillumination images are acquired with annular on-axis or laterally-displaced off-axis apertures that capture scattered light and reject the retroreflected light used for reflectance imaging. SLO axial resolution is roughly 300 μm, comparable to macular thickness, so SLOs cannot provide the depth-resolved chorioretinal information obtainable with optical coherence tomography’s (OCT’s) 3 μm axial resolution. Retroillumination highlights and shades the boundaries of chorioretinal tissues and abnormalities, facilitating detection of small drusen, subretinal drusenoid deposits and subthreshold laser lesions. It also facilitates screening for large-area chorioretinal irregularities not readily identified with other en face retinal imaging modalities. Shaded boundaries create the perception of lesion elevation or depression, a characteristic of retroillumination but not reflectance SLO images. These illusions are not reliable representations of three-dimensional chorioretinal anatomy and they differ from objective OCT en face topography. SLO retroillumination has been a useful but not indispensable retinal imaging modality for over 30 years. Continuing investigation is needed to determine its most appropriate clinical roles in multimodal retinal imaging.

Reticular Pseudodrusen on the Risk of Progression in Intermediate Age-Related Macular Degeneration

PURPOSE

To examine the association between reticular pseudodrusen (RPD) and progression to late age-related macular degeneration (AMD) in individuals with intermediate AMD.

DESIGN

Prospective cohort study.

METHODS

Two hundred eighty eyes from 140 participants with bilateral large drusen underwent multimodal imaging (MMI), including optical coherence tomography (OCT), near-infrared reflectance (NIR), fundus autofluorescence, and color fundus photography (CFP), at 6-monthly intervals up over a 36-month follow-up period. The presence of RPD per eye was determined based on either a combined MMI criterion, or each individual imaging modality, and their extent measured on combined OCT and NIR imaging. The association between the presence of RPD on different imaging modalities, and their extent, with the development of late AMD (including OCT-defined atrophy) was evaluated.

RESULTS

The presence of RPD on MMI, or any of its individual modalities, at baseline was not significantly associated with an increased rate of developing late AMD, with or without adjusting for risk factors for AMD progression (age, drusen volume on OCT, and pigmentary abnormalities on CFP; all P ≥ 0.205). The extent of RPD present was also not significantly associated with an increased rate of developing late AMD, with or without adjustment for risk factors for AMD progression (both P ≥ 0.522).

CONCLUSIONS

In this cohort with bilateral large drusen, the presence of RPD was not significantly associated with an increased risk of developing late AMD. Additional longitudinal studies in all stages of AMD are needed to understand the implications of RPD on vision loss in this condition.

Multispectral pattern recognition measures change in drusen area in age-related macular degeneration with high congruency to expert graders

Drusen are a hallmark lesion of age-related macular degeneration (AMD) and changes in their area and/or volume are strongly associated with disease progression. Assessment of longitudinal change in drusen size in clinical practice however is limited to a single commercial tool or manual inspection by clinicians. In this study we analysed change in drusen area in 33 eyes with intermediate AMD across two separate visits using a novel technique known as multispectral pattern recognition for en face retinal images from various imaging modalities (infrared (815 nm), fundus autofluorescence (488 nm) and green (532 nm) scanning laser ophthalmoscopy). We found 91% (30/33 eyes) agreement in the direction of drusen change for multispectral pattern recognition relative to expert graders who graded eyes as having drusen progression, regression or being stable. Multispectral pattern recognition showed 100% sensitivity (22/22 eyes) and 73% specificity (8/11 eyes). In comparison, we found only 70% (23/33 eyes) agreement in the direction of drusen change with a commercially available change analysis software, the Cirrus Advanced RPE Analysis relative to expert graders, with a sensitivity 64% (14/22 eyes) and specificity of 82% (9/11 eyes). Total drusen area or amount of change between visits had no significant effect on agreement. This suggests multispectral pattern recognition can quantify longitudinal change in drusen area from multimodal imaging with greater congruency to expert graders than a commercially available platform based on a single imaging modality. Considering the association of drusen area and disease progression, this method could aid clinical assessment and monitoring of AMD.

Subretinal drusenoid deposits: An update

A wide spectrum of phenotypic manifestations characterizes age-related macular degeneration (AMD). Drusen is considered the hallmark of AMD and is located underneath the retinal pigment epithelium (RPE). In contrast, subretinal drusenoid deposits (SDDs), also known as reticular pseudodrusens, are located in the subretinal space, on top of the RPE. SDDs are poorly detected by clinical examination and color fundus photography. Multimodal imaging is required for their proper diagnosis. SDDs are topographically and functionally related to rods. SDDs cause a deep impairment in retinal sensitivity and dark adaptation. SDDs are dynamic structures that may grow, fuse with each other, or regress over time. An intermediate step in some eyes is the development of an acquired vitelliform lesion. The presence of SDD confers an eye a high risk for the development of late AMD. SDD leads to macular neovascularization, particularly type 3, geographic atrophy, and outer retinal atrophy.

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.

Retro mode illumination for detecting and quantifying the area of geographic atrophy in non-neovascular age-related macular degeneration

PURPOSE

To evaluate the ability of retro mode illumination imaging for quantifying atrophy compared to confocal color fundus photography (c-CFP), green light fundus autofluorescence (G-FAF), blue light fundus autofluorescence (B-FAF) using the scanning laser ophthalmoscope (SLO) Mirante device by Nidek (Nidek Co., Ltd, Gamogori, Japan).

METHODS

Eyes with clinical evidence of geographic atrophy (GA) associated with non-neovascular age-related macular degeneration, evaluated at the Doheny Eye Centers-UCLA and Hospital Sacco Milan, were included in this prospective, cross-sectional study. All eyes were imaged with multiple retinal imaging modalities using the SLO Nidek Mirante device: c-CFP, G-FAF, B-FAF, retro mode illumination deviated-right (RMDR), and deviated-left (RMDL). Masked graders measured the GA lesion on each modality and inter-modality and inter-grader repeatability were assessed.

RESULTS

The mean (SD) area of GA measured 9.76 (3.82) mm², 9.75 (3.91) mm², 9.76 (3.92) mm², 9.82 (3.87) mm², and 9.81 (3.86) mm² using c-CFP, G-FAF, B-FAF, RMDR, and RMDL, respectively (p = 0.2). Inter-modality correlation was high (Pearson's r > 0.9 and p < 0.0001). Agreement between graders was excellent for all modalities.

CONCLUSIONS

Retro mode imaging demonstrated good agreement for measuring GA compared to other imaging modalities, with a high level of repeatability. Given that retro mode imaging uses infrared light and is comfortable, it may prove to be a useful tool for the assessment of GA in the clinic.

Scotopic thresholds on dark-adapted chromatic perimetry in healthy aging and age-related macular degeneration

To evaluate the effect of aging, intra- and intersession repeatability and regional scotopic sensitivities in healthy and age-related macular degeneration (AMD) eyes. Intra- and intersession agreement and effect of age was measured in healthy individuals. The mean sensitivity (MS) and pointwise retinal sensitivities (PWS) within the central 24° with 505 nm (cyan) and 625 nm (red) stimuli were evaluated in 50 individuals (11 healthy and 39 AMD eyes). The overall intra- and intersession had excellent reliability (intraclass correlation coefficient, ICC > 0.90) and tests were highly correlated (Spearman r_s = 0.75-0.86). Eyes with subretinal drusenoid deposit (SDD) had reduced PWS centrally, particularly at inferior and nasal retinal locations compared with controls and intermediate AMD (iAMD) without SDD. There was no difference in MS or PWS at any retinal location between iAMD without SDD and healthy individuals nor between iAMD with SDD and non-foveal atrophic AMD groups. Eyes with SDD have reduced rod function compared to iAMD without SDD and healthy eyes, but similar to eyes with non-foveal atrophy. Our results highlight rod dysfunction is not directly correlated with drusen load and SDD location.

Multimodal imaging in a case of best vitelliform macular dystrophy

We describe a case of Best Vitelliform Macular Dystrophy using the Mirante device by Nidek, a multi-modal confocal scanning laser ophthalmoscopy (SLO) system equipped with Retro Mode Illumination, a relatively new retinal imaging modality.

Comparison between two multimodal imaging platforms: Nidek Mirante and Heidelberg Spectralis

PURPOSE

To investigate the reliability and comparability of retinal measurements obtained with spectral-domain optical coherence tomography (OCT), optical coherence tomography angiography (OCTA), confocal scanning laser ophthalmoscopy (cSLO) colour images, and fundus autofluorescence (FAF) between two multimodal imaging platforms in eyes with macular pathology and normal, healthy volunteers.

METHODS

This cross-sectional, multi-centre, instrument validation study recruited 94 consecutive subjects. All participants underwent a dilated examination and were scanned consecutively on the Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) and Nidek Mirante (Nidek Co. Ltd., Gamagori, Japan) devices. Agreement between device images were evaluated from measures of the central retinal thickness (CRT), presence of segmentation and fixation imaging artefacts (IA), foveal avascular zone (FAZ) measurements; as well as sensitivity and specificity values from the detection of atrophy on fundus autofluorescence (FAF), drusen, subretinal drusenoid deposits, geographic atrophy, epiretinal membrane, fibrosis and haemorrhage on multicolour imaging, and agreement between devices and groups.

RESULTS

Compared with reference clinical examination, sensitivity values for the identification of retinal features using sole device images ranged from 100% for epiretinal membranes to 66.7% for subretinal drusenoid deposits (SSD). Mean absolute difference for CRT between OCT devices was 3.78 μm (95% confidence interval [CI]: - 21.39 to 28.95, P = 0.809). Differences in the superficial and deep capillary plexus FAZ area on OCTA between devices were not statistically significant (P = 0.881 and P = 0.595, respectively). IAs were significantly increased in the presence of macular pathology.

CONCLUSION

Comparison of retinal measurements between the OCT devices did not differ significantly. Common ultrastructural biomarkers of multiple macular pathologies were identified with high sensitivities and specificities, with good agreement between graders, indicating that they can be identified with comparable confidence in retinal imaging between the two devices.