Imaging of Melanin Disruption in Age-Related Macular Degeneration Using Multispectral Imaging

Multispectral imaging: Review of current applications

Multispectral imaging (MSI) is a unique layer-by-layer imaging technique that allows the visualization of a wide array of retinal and choroidal pathologies including retinovascular disorders, retinal pigment epithelial changes, and choroidal lesions. Herein, we summarize the basic imaging principles and current applications of MSI together with recent technology advances in the field. MSI detects reflectance signal from both normal chorioretinal tissue and pathological lesions. Either hyperreflectance or hyporeflectance reveals the absorption activity of pigments such as hemoglobin and melanin and the reflection from interfaces such as the posterior hyaloid. Advances in MSI technique include creation of a retinal and choroidal oxy-deoxy map that could provide a better understanding of blood oxygen saturation within lesions as well as better interpretation of reflectance phenomenon of MSI images such as the different reflectance from the Sattler and Haller layers described in this review.

Single-cell RNA sequencing reveals transcriptional changes of human choroidal and retinal pigment epithelium cells during fetal development, in healthy adult and intermediate age-related macular degeneration

Age-related macular degeneration (AMD) is the most prevalent cause of blindness in the developed world. Vision loss in the advanced stages of the disease is caused by atrophy of retinal photoreceptors, overlying retinal pigment epithelium (RPE) and choroidal endothelial cells. The molecular events that underline the development of these cell types from in utero to adult as well as the progression to intermediate and advanced stages AMD are not yet fully understood. We performed single-cell RNA-sequencing (RNA-Seq) of human fetal and adult RPE-choroidal tissues, profiling in detail all the cell types and elucidating cell type-specific proliferation, differentiation and immunomodulation events that occur up to midgestation. Our data demonstrate that progression from the fetal to adult state is characterized by an increase in expression of genes involved in the oxidative stress response and detoxification from heavy metals, suggesting a better defence against oxidative stress in the adult RPE-choroid tissue. Single-cell comparative transcriptional analysis between a patient with intermediate AMD and an unaffected subject revealed a reduction in the number of RPE cells and melanocytes in the macular region of the AMD patient. Together these findings may suggest a macular loss of RPE cells and melanocytes in the AMD patients, but given the complex processing of tissues required for single-cell RNA-Seq that is prone to technical artefacts, these findings need to be validated by additional techniques in a larger number of AMD patients and controls.

Multi-spectral imaging in adult-onset foveomacular vitelliform dystrophy: Report of two cases

Purpose

To describe the characteristic findings of non-invasive multi-spectral imaging (MSI) for adult-onset foveomacular vitelliform dystrophy (AFVD).

Observations

On examination of MSI, the characteristic performances of AFVD include the nodule-like high-reflecting lesions, the line-like low-reflecting lesions in the high-reflecting lesion, and the scattered high-reflecting and low-reflecting lesions around the nodule-like lesion. MSI has an advantage over color fundus photography (CFP) and fundus autofluorescence (FAF) in finding tiny lesions, which corresponded to drusenoid structures on optical coherence tomography (OCT). MSI showed different characteristics at different stages of AFVD, which may be instructive to the pathogenesis and progression of AFVD.

Conclusions and Importance

MSI is a promising diagnostic and follow-up tool that will provide additional information in fundus imaging for AFVD, and the changes on MSI is partially instructive to the pathogenesis and progression of AFVD.

SENSITIVITY AND SPECIFICITY OF MULTISPECTRAL IMAGING FOR POLYPOIDAL CHOROIDAL VASCULOPATHY

PURPOSE

To evaluate the sensitivity and specificity of multispectral imaging (MSI), a noninvasive imaging technique composed of a series of monochromatic scanning light, for polypoidal choroidal vasculopathy (PCV).

METHODS

This was a prospective observational study. Polypoidal lesions on MSI are defined by oval or lobular hyperreflective oval lesion with dark hyporeflective center. Branching vascular networks on MSI is featured by hyperreflective interlacing signal. Detection sensitivity and specificity of polypoidal lesions was compared with indocyanine green angiography, whereas sensitivity and specificity of branching vascular networks, subretinal fluid, and pigment epithelium detachment were compared with optical coherence tomography.

RESULTS

Among 67 eyes, 38 eyes (56.7%) were diagnosed with PCV, 7 eyes (10.4%) with neovascular age-related macular degeneration, 13 eyes (19.4%) with central serous chorioretinopathy, 6 eyes (9.0%) with pathological myopia, and 3 eyes (4.5%) with idiopathic choroidal neovascularization. Compared with indocyanine green angiography, the sensitivity and specificity for diagnosing PCV by MSI alone was 84.21% and 93.10%, respectively, and the positive predictive value and the negative predictive value for PCV by MSI was 94.12% and 81.82%, respectively. The sensitivity and specificity for detecting polypoidal lesions were 84.21% and 93.10% compared with indocyanine green angiography. Compared with optical coherence tomography, the sensitivity and specificity for detecting branching vascular networks were 95.83% and 88.37%, for the subretinal fluid were 76.92% and 86.67%, and for the pigment epithelium detachment were 91.11% and 90.91%, respectively.

CONCLUSION

Multispectral imaging allowed noninvasive visualization of polypoidal lesions and branching vascular networks and may serve as a new diagnostic option for PCV.

The impact of mass spectrometry application to screen new proteomics biomarkers in Ophthalmology

INTRODUCTION

In the search for molecular markers that aid in the early diagnosis and treatment of various human diseases, many studies have focused on changes in genes, their transcripts and protein products. Recent advances in proteomic methodologies, such as mass spectrometry (MS), generate new opportunities to obtain relevant information on normal and abnormal processes that occur in many important cell pathways. The human eye is a highly specialized and compartmentalized organ, and the interpretation of molecular biomarkers helps to evaluate its cellular structure, providing a broader molecular understanding that corroborates in the pathophysiology of ophthalmological diseases, with marked improvements in their diagnosis, prognosis and treatment. This review summarizes the most important protein biomarkers in Ophthalmology screened by MS tools.

CONCLUSION

The use of translational medicine techniques (as MS), integrating basic and clinical research, still transforms scientific findings, from laboratory researches to clinical applications, from the bedside into the community.

Characteristics of punctate inner choroidopathy complicated by choroidal neovascularisation on Multispectral Imaging in comparison with other imaging modalities

PURPOSE

To describe the characteristics seen on multispectral imaging (MSI) in patients with punctate inner choroidopathy (PIC) and choroidal neovascularisation (CNV) and compare the findings with current standard multimodal imaging techniques.

METHODS

This is a retrospective observational case series of 10 patients with PIC complicated by CNV that underwent multimodal retinal imaging examinations.

RESULTS

Twelve eyes of 10 patients were included. CNV was identified in 11 of the 12 eyes (91.7%) by MSI with nodular or trunk-like hyperreflectance on retinal oxy/deoxyhemoglobin map. MSI revealed choroidal vasculature around CNV in 91.7% eyes and pathological changes including retinal pigment epithelial atrophy and melanin disruption of punctate lesions in all eyes.

CONCLUSION

MSI helps in noninvasively detecting CNV in PIC patients and observing associated changes in choroidal vasculature. This imaging technique is also a promising tool for better tracking pathological changes of PIC lesions complementary to current standard multimodal imaging modalities.

Novel observations in choroidal osteoma by multispectral imaging: a pilot case series

PURPOSE

To identify novel tumor-specific features of ossification by using multispectral imaging (MSI) in patients diagnosed with choroidal osteoma.

METHODS

Six eyes of 5 patients previously diagnosed with choroidal osteoma by ocular ultrasonography and orbital computerized tomography were observed with multispectral imaging (MSI). Traditional multimodal imaging, including color fundus photograph (CFP) and enhanced depth-imaging-optical coherence tomography (EDI-OCT), fundus autofluorescence (FAF), indocyanine green angiography/fundus fluorescein angiography (ICGA/FFA), was performed. Osseous features detected by MSI such as calcification and decalcification were characterized and compared with other imaging modalities.

RESULTS

In all 3 eyes with calcified choroidal osteoma (100%), MSI featured by the homogeneous reflectance in 550 nm but the beehive appearance in 600-680 nm and homogenous hyper-reflectance in 780-850 nm', indicating the compact bone in the outer layers and bone trabecula in the middle layer (Sandwich sign). The pigmentary change showed high agreement between MSI and FAF. In other 3 eyes with extensive decalcification, MSI was able to differentiate the inactive portion of the osteoma from the decalcified area. The inactive portion was characterized by geographic hyper-reflective islands with higher reflectivity border (floating island sign). Decalcified portion was featured by increased definition and reflectivity from osteoma. Partial decalcification and total decalcification can be differentiated in one decalcifying eye (33.3%). MSI revealed better the presence and border of the osteoma compared with FFA, FAF and MC (100%) in all six eyes in our study.

CONCLUSIONS

MSI presented characteristic osseous-related features of choroidal osteoma, providing clear evidence for differentiating osteoblastic and osteoclastic regions and noncalcifying regions. It can contribute to en-face visualization of choroidal osteomas at different stages, providing new insight into the spectrum behavior of CO.

Analysis of skin morphological features and real-time monitoring using snapshot hyperspectral imaging

We propose a snapshot hyperspectral imaging system and methods for skin morphological feature analysis and real-time monitoring of skin activities. The analysis method includes a strategy using weighted subtractions between sub-channel images to extract absorption information due to specific chromophores within skin tissue, for example hemoglobin and melanin. Based on morphological analysis results, we carry out real-time monitoring of the skin features to verify the ability of this method to provide temporal responses of the skin tissue activities, which is experimentally shown to be useful in the measurement of heartrate, monitoring of the tissue recovery after a body exercise, and studying of the tissue response due to a vascular occlusion. Compared to conventional multispectral imaging system, the proposed system improves the device simplicity and is immune to motion artifacts. Coupled with the extraction algorithms, the hyperspectral imaging promises a robust skin assessment tool with abilities for qualitative visualization and potentially quantitative analysis of skin features, useful in the applications of cosmetics and clinical dermatology.

HtrA1 Mediated Intracellular Effects on Tubulin Using a Polarized RPE Disease Model

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss. The protein HtrA1 is enriched in retinal pigment epithelial (RPE) cells isolated from AMD patients and in drusen deposits. However, it is poorly understood how increased levels of HtrA1 affect the physiological function of the RPE at the intracellular level. Here, we developed hfRPE (human fetal retinal pigment epithelial) cell culture model where cells fully differentiated into a polarized functional monolayer. In this model, we fine-tuned the cellular levels of HtrA1 by targeted overexpression. Our data show that HtrA1 enzymatic activity leads to intracellular degradation of tubulin with a corresponding reduction in the number of microtubules, and consequently to an altered mechanical cell phenotype. HtrA1 overexpression further leads to impaired apical processes and decreased phagocytosis, an essential function for photoreceptor survival. These cellular alterations correlate with the AMD phenotype and thus highlight HtrA1 as an intracellular target for therapeutic interventions towards AMD treatment.

Multi-Spectral Imaging of Circumscribed Choroidal Hemangioma Introduction

BACKGROUND AND OBJECTIVE

To illustrate the features of a circumscribed choroidal hemangioma (CCH) using Annidis RHA multi-spectral imaging (MSI) technology (Annidis Corporation, Ottawa, Canada). This novel imaging technique uses non-overlapping, narrow-band LED light sources ranging from 520 nm to 940 nm to create a monochromatic series of en face fundus images and oxy/deoxyhemoglobin contrasted maps of the retina and choroid.

PATIENTS AND METHODS

Annidis RHA MSI images were taken of a 67-year-old Chinese male with CCH. These en face fundus images are presented alongside the traditional fundus photograph, optical coherence tomography, and fluorescein and indocyanine green angiograms.

RESULTS

Multi-spectral en face images of the outer retina and choroid demonstrated a clearly delineated lesion with a disorganized choroidal vascular network and increased reflectance/ oxyhemoglobin levels within.

CONCLUSION

MSI technology is a noninvasive imaging technique that can depict the vascular features and choroidal oxygenation of CCH lesions and has a potential role in monitoring its growth complications. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:572-575.].

The nanomechanical role of melanin granules in the retinal pigment epithelium

Nanomechanical properties of cells and tissues, in particular their elasticity, play an important role in different physiological and pathological processes. Recently, we have demonstrated that melanin granules dramatically modify nanomechanical properties of melanoma cells making them very stiff and, as a result, less aggressive. Although the mechanical effect of melanin granules was demonstrated in pathological cells, it was never studied in the case of normal cells. In this work, we analyzed the impact of melanin granules on nanomechanical properties of primary retinal pigment epithelium tissue fragments isolated from porcine eyes. The obtained results clearly show that melanin granules are responsible for the exceptional nanomechanical properties of the tissue. Our findings suggest that melanin granules in the retinal pigment epithelium may play an important role in sustaining the stiffness of this single cell layer, which functions as a natural mechanical barrier separating the retina from the choroid.

A case study of choroideremia carrier - Use of multi-spectral imaging in highlighting clinical features

Purpose

To report the use of non-invasive multi-spectral imaging of a female choroideremia (CHM) carrier with mild visual symptoms and extensive fundus mottling.

Observation

This was an observational case report study. A symptomatic 42-year-old female with a history of binocular CHM presented for routine ocular examination and underwent review of her clinical and photographic records, optical coherence tomography (OCT), intravenous fluorescein angiography (IVFA) and multi-spectral imaging (MSI). Dilated fundus examination and photography revealed similar outcomes of diffuse mottling with normal looking vessels. IVFA showed large irregular and confluent patches of RPE atrophy in the peripapillary and parapapillary areas as well as the midperiphery, corresponding to the OCT findings. The entire range of MSI imaging (520–940 nm) clearly illustrated the anomalies of the fundus including retinal pigment epithelium (RPE) mottling with melanin clumping not readily seen with the other imaging modalities. MSI fundus autofluorescence (MSI-FAF) showed a spotty hypo and hyperautofluorescent appearance of the fundus, consistent with the observations seen on IVFA and OCT images.

Conclusion and Importance

MSI significantly improves visualization of the retinal pigment epithelium in choroideremia. The non-invasive nature of MSI technique is a valuable tool in monitoring the effect of retinal and choroidal presentation in patients with CHM.