Retro-mode imaging and fundus autofluorescence with scanning laser ophthalmoscope of retinal dystrophies

Retro Mode Imaging for Detection and Quantification of Sub-RPE Drusen and Subretinal Drusenoid Deposits in Age-Related Macular Degeneration

Background: Drusen and drusenoid deposits are a hallmark of age-related macular degeneration (AMD). Nowadays, a multimodal retinal imaging approach enables the detection of these deposits. However, quantitative data on subretinal drusenoid deposits (SDDs) are still missing. Here, we compare the capability of en-face drusen and SDD area detection in eyes with non-exudative AMD using conventional imaging modalities versus Retro mode imaging. We also quantitatively assess the topographic distribution of drusen and SDDs. Methods: In total, 120 eyes of 90 subjects (mean age ± standard deviation = 74.6 ± 8.6 years) were included. Coherent en-face drusen and SDD areas were measured via near-infrared reflectance, green (G-) and blue (B-) fundus autofluorescence (AF), and Retro mode imaging. Drusen phenotypes were classified by correlating en-face drusen areas using structural high-resolution spectral domain optical coherence tomography. The topographic distribution of drusen was analyzed according to a modified ETDRS (Early Treatment of Diabetic Retinopathy Study) grid. Intraclass correlation coefficient (ICC) analysis was applied to determine the inter-reader agreement in the SDD en-face area assessment. Results: The largest coherent en-face drusen area was found using Retro mode imaging with a mean area of 105.2 ± 45.9 mm2 (deviated left mode (DL)) and 105.4 ± 45.5 mm2 (deviated right mode (DR)). The smallest en-face drusen areas were determined by GAF (50.9 ± 42.6 mm2) and BAF imaging (49.1 ± 42.9 mm2) (p < 0.001). The inter-reader agreement for SDD en-face areas ranged from 0.93 (DR) to 0.70 (BAF). The topographic analysis revealed the highest number of SDDs in the superior peripheral retina, whereas sub-retinal pigment epithelium drusen were mostly found in the perifoveal retina. Retro mode imaging further enabled the detection of the earliest SDD stages. Conclusions: Retro mode imaging allows for a detailed detection of drusen phenotypes. While hundreds/thousands of SDDs can be present in one eye, the impact of SDD number or volume on AMD progression still needs to be evaluated. However, this new imaging modality can add important knowledge on drusen development and the pathophysiology of AMD.

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.

Retro-Mode in NIDEK Mirante: A Comparative Analysis with Other Imaging Modalities for AMD and CSR

BACKGROUND

Retro-mode is a novel technique capable of creating pseudo-3D images of the retina. However, its clinical utility remains unknown. This study aimed to evaluate the Nidek Mirante multimodal imaging platform for ocular assessment in patients with various retinal conditions.

METHODS

A total of 115 participants with central serous chorioretinopathy (CSR) and age-related macular degeneration (AMD) were included. Two experienced graders independently evaluated the images, and statistical analysis was performed to assess interclass correlation coefficients (ICC) between graders and modalities; Results: For CSR detection, retro-mode demonstrated exceptionally high ICC rates (ICC = 1; 100%), while color and autofluorescence (FAF) showed moderate coefficients (0.69 and 0.78, respectively). The detection of pigment epithelial detachment was high across all methods, with only retro-mode deviated right (DR) allowing detection in 69% of cases, while retro-mode DR and deviated left (DL) achieved 100% detection. FAF-green achieved a 95% detection rate. In detecting retinal atrophy, most modalities demonstrated high detection rates, with the lowest detection rates offered by retro-mode DL (ICC = 0.85) and DR (ICC = 0.89), while retro-mode ring aperture offered 0.97. Infra-red and fluorescein angiography imaging offered the highest detection rates among the tested modalities, with 97% and 100%, respectively.

CONCLUSION

Retro-mode showed promise for comprehensive ocular evaluation and diagnosis, with certain imaging modalities demonstrating higher accuracy in detecting specific retinal features.

Retro-mode: a newer insight into dry age-related macular degeneration (AMD)

The purpose of this study is to study the role of retro-mode (RM) in early detection and to compare it with other preexisting available modalities on multimodal imaging system in dry AMD. A prospective observational cross-sectional study was done between November 2020 and October 2021 which included 409 eyes of 207 patients. For study purpose, eyes were divided into 3 groups according to the size and number of the drusen, viz, group 1: No AMD, group 2: early AMD and group 3: intermediate AMD which was further divided into 2 subgroups, viz, subgroup A: eyes with drusen size 63-125 μm and subgroup B: eyes with drusen size 125-250 μm. Patients with active or treated wet AMD, scarred choroidal neovascular membrane (CNVM), other maculopathies, other retinopathies, high myopia, trauma and glaucoma were excluded from the study. In cases of No AMD and early AMD, a number of drusens detected on RM were statistically not significant compared to fundus autofluorescence (FAF) and color photo (CF), but in intermediate AMD cases, it was statistically significant. While the area involved by drusens calculated by RM was statistically significant compared to both other modalities. When all modalities were compared with enhanced depth imaging-optical coherence tomography (EDI-OCT) at the choroid and chorio-capillary (CC) level and vessel density (VD) on optical coherence tomography angiography (OCTA) at the choroid, capillaries, deep retinal and superficial retinal plexus level; it was only RM which was found to be in sync with these proven modalities in terms of pattern and trend. In the present scenario, RM is found to be a better diagnostic modality in detecting early and a greater number of drusens with area of involvement than other existing modalities. Though superior, as found in this study, this mode cannot replace other modalities at present but only acts as a complementary investigation in early detection of this disease.

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.

Morphological Features of Full-Thickness Macular Holes Using Retromode Scanning Laser Ophthalmoscopy

BACKGROUND AND OBJECTIVE

Retromode scanning laser ophthalmoscopy (RM-SLO) is a new imaging modality displaying pseudo-3D retinal images. We assessed the correlation between the morphological features of full-thickness macular holes (FTMHs) when using spectral domain-optical coherence tomography (SD-OCT) and when using RM-SLO.

MATERIALS AND METHODS

This is a prospective observational case series in which patients were examined through SD-OCT and RM-SLO after informed consent was obtained. Intraclass correlation coefficient (ICC) and Pearson correlation coefficient (PCC) were used to assess interobserver agreement and the correlation between the diameters measured with the two techniques.

RESULTS

We enrolled 20 patients (20 eyes) with an average hole aperture size of 426 μm (140-890 μm) on SD-OCT and 56 pixels (19-102 pixels) on RM-SLO. ICC and PCC were 0.999 and 0.992, respectively. "Standard" and "double-ring" FTMH patterns were described on RM-SLO and related well with SD-OCT findings.

CONCLUSIONS

RM-SLO is a reliable method for FTMH-diameter evaluation and identifies unique pseudo-3D morphological features consistent with their B-scan counterparts. [Ophthalmic Surg Lasers Imaging Retina 2022; 53:368-373.].

Novel mutations in c2orf71 causing an early onset form of cone-rod dystrophy: A molecular diagnosis after 20 years of clinical follow-up

Purpose

Cone rod-dystrophies (CRDs) are pigmentary retinopathies mainly involving cones. CRDs typically present with decreased visual acuity and loss of sensitivity in the central visual field, reflecting the primary dysfunction of cones associated with night blindness and concentric visual field loss due to rod dysfunction. We describe the phenotype, natural history, and molecular analysis results of an early onset form of CRD.

Methods

An otherwise healthy 25-year-old man from Sardinia, Italy, initially presented with subacute visual loss and central scotoma in both eyes. He underwent a complete ophthalmic examination, electrophysiologic testing, and genetic counseling. We first applied a candidate gene approach on ABCA4 to detect mutations; then, we performed exome sequencing (WES) on all family members to identify causative mutations.

Results

The ophthalmic examination was unremarkable except the fundus examination, which revealed a well-circumscribed ring-shaped area of choroidal and RPE atrophy surrounding the fovea in the left eye and small white patches of atrophy around the fovea in the right eye. The ocular features and medical history were consistent with a diagnosis of CRD. Twenty years later, he showed a marked impairment in visual function, secondary to severe atrophic maculopathy associated with sparse pigmentary deposits. Molecular analysis identified two novel frameshift mutations in C2orf71: c.3039dupC: p.Ser1014Leufs*93 and c.1804_1805delAG:p. His603Argfs*77.

Conclusions

The mutations in C2orf71 reported in this study comprise protein truncation mutations, which are likely to be involved in the pathogenesis of this severe form of early onset CRD.

Near-Infrared Fundus Autofluorescence in Multiple Evanescent White-Dot Syndrome

Purpose

To report the near-infrared fundus autofluorescence (NIR-FAF) pattern in 2 cases of multiple evanescent white-dot syndrome (MEWDS).

Methods

Three consecutive patients with MEWDS underwent a complete ophthalmologic examination, including color photograph, blue-light fundus autofluorescence, NIR-FAF, fluorescein angiography, and indocyanine green angiography (ICGA). Main outcome measure was the identification of NIR-FAF pattern.

Results

Fluorescein angiography showed patchy hyperfluorescence of the whitish dots. Indocyanine green angiography showed hypofluorescent spots throughout the examination. Blue-light fundus autofluorescence disclosed a speckled pattern without extension to the foveal area, whereas NIR-AF showed several hypoautofluorescent lesions involving also the fovea, which corresponded to the whitish dots visible on biomicroscopy and to the hypofluorescent lesions detectable on ICGA.

Conclusions

Near-infrared fundus autofluorescence is characterized by hypoautofluorescent spots corresponding to the inflammatory lesions typical of MEWDS and can be considered as a valuable noninvasive technique to diagnose and monitor patients with MEWDS.

Hereditary retinal eye diseases in childhood and youth affecting the central retina

Hereditary dystrophies affecting the central retina represent a heterogeneous group of diseases. Mutations in different genes may be responsible for changes of the choroid (choroideremia), of the retinal pigment epithelium [RPE] (Best's disease), of the photoreceptor outer segments (Stargardt's disease) and of the bipolar and Mueller cells (x-linked retinoschisis). The correct diagnosis of hereditary retinal dystrophies is important, even though therapeutic options are limited at the moment, as every patient should get a diagnosis and be informed about the expected prognosis. Furthermore, specific gene therapy of a number of diseases such as Leber congenital amaurosis, choroideremia, Stargardt's disease, Usher Syndrome and achromatopsia is being evaluated at present. Classic examinations for patients suffering from hereditary retinal dystrophies of the central retina are funduscopy - also using red-free light - visual-field tests, electrophysiologic tests as electro-retinogram [ERG] and multifocal ERG and tests evaluating color vision. Recently, new imaging modalities have been introduced into the clinical practice. The significance of these new methods such as high-resolution spectral-domain optic coherence tomography [SD-OCT] and fundus autofluorescence will be discussed as well as "next generation sequencing" as a new method for the analysis of genetic mutations in a larger number of patients.

The noninvasive retro-mode imaging of confocal scanning laser ophthalmoscopy in myopic maculopathy: a prospective observational study

PURPOSE

To investigate the morphological features of myopic maculopathy with a new and noninvasive retro-mode imaging (RMI) technique using a confocal scanning laser ophthalmoscope.

METHODS

A total of 42 patients (69 eyes) with myopic maculopathy were included. RMI combined with fundus photography, fundus fluorescein angiography, and optical coherence tomography together were used to observe and evaluate the morphological features of disease.

RESULTS

Four in 4 eyes (100%) with macular retinoschisis were found with a characteristic pattern by RMI (firework pattern centrally with surrounding fingerprint pattern). Twenty-four in 24 eyes (100%) with pigment proliferation were found by RMI as dark plain patches, and 23 in 24 eyes with hemorrhage (95.8%) were found by RMI as gray bump. Atrophy of different degrees (12 in 14 eyes, 85.7%) was found by RMI as an area of pseudo-3D choroidal vessels or a fuzzy shadow but both without a clear boundary. Choroidal neovascularization (12 in 16 eyes, 75%) was identified laboriously by RMI as a vague raised region. Lacquer cracks were difficult to figure out in RMI.

CONCLUSIONS

Retinoschisis, pigment proliferation, hemorrhage, and atrophy secondary to myopic maculopathy have characteristic morphologic features in RMI; however, choroidal neovascularization and lacquer crack are not easily distinguishable in RMI.

Retromode imaging: Review and perspectives

Retromode imaging with infrared lasers is a novel imaging method which has been made possible by the newly introduced confocal scanning laser ophthalmoscope. Retromode imaging uses a laterally deviated confocal aperture with a central stop, which creates a shadow and allows deep retinal and retinal pigment epithelium changes to be visualized as pseudo-3-dimensional images. Its clinical value coupled with its simple, rapid, and noninvasive nature is increasingly appreciated. The combination of retromode imaging with conventional imaging methods such as fundus photography, fluorescein angiography, and optical coherence tomography can help to precisely and comprehensively evaluate pathophysiologic features of retinal disorders. This review summarizes basic principles of imaging and retromode findings in various retinal disorders and is expected to guide future investigations of retromode imaging.

The noninvasive retro-mode imaging modality of confocal scanning laser ophthalmoscopy in polypoidal choroidal vasculopathy: a preliminary application

PURPOSE

To evaluate the validity of the novel and noninvasive retro-mode imaging modality of confocal scanning laser ophthalmoscopy (cSLO) for detecting the morphological features of polypoidal choroidal vasculopathy (PCV).

DESIGN

Prospective, observational, consecutive case series.

METHODS

Twenty-six patients (29 eyes) with PCV were enrolled in this study. All patients underwent comprehensive ophthalmologic examinations and imaging studies, including retro-mode imaging, fundus autofluorescence (FAF), fundus photography, fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA) and spectral-domain optical coherence tomography (SD-OCT). We investigated the retro-mode images and compared the results with those of SD-OCT, FFA and ICGA.

RESULTS

In the 29 PCV eyes, the retro-mode images clearly revealed polypoidal lesions in 27 (93.1%) eyes as well as branching vascular networks in 16 (55.2%) eyes. Others findings, including pigment epithelial detachment (PED) in 20 (69.0%) eyes, neuroretinal detachment (NRD) in 3 (10.3%) eyes, cystoid macular edema (CME) in 3 (10.3%) eyes, drusen in 4 (13.8%) eyes and minute granular changes of the retinal pigment epithelium (RPE) in 12 (41.3%) eyes, were also clearly visualized. When we compared the results with those of SD-OCT, FFA and ICGA, there was no significant difference between ICGA and retro-mode imaging for finding polypoidal lesions and (or) branching choroidal vascular networks (P>0.05). However, the rate of PED detection was significantly better with retro-mode imaging than with the ICGA (P<0.05). The differences were not statistically significant between SD-OCT and retro-mode imaging for detecting PED, NRD, CME, drusen and minute granular RPE changes (P>0.05). The differences were not statistically significant between FFA and retro-mode imaging for detecting PED, NRD, CME (P>0.05).

CONCLUSIONS

The novel and noninvasive retro-mode imaging by cSLO is able to clearly visualize the morphological features of PCV.