Granular lesions of short-wavelength and near-infrared autofluorescence in diabetic macular oedema

Fundus Autofluorescence in Diabetic Retinopathy

Diabetic retinopathy is a leading cause of visual morbidity worldwide. Fundus autofluorescence is a rapid, non-invasive imaging modality that has gained increased popularity in recent years in the multimodal evaluation of diabetic retinopathy and, in particular, of diabetic macular oedema. Acquired using either a fundus camera or the confocal scanning laser ophthalmoscope, short-wavelength and near-infrared autofluorescence are the most used techniques in diabetic retinopathy. In diabetic macular oedema, short-wavelength autofluorescence, in its cystoid pattern, is useful for detecting cystoid macular oedema. Increased spot hyperautofluorescence in short-wavelength and granular changes in near-infrared autofluorescence correlate well with other imaging findings, indicating photoreceptor and retinal pigment epithelium damage and being associated with decreased visual acuity. While also being a marker of oxidative stress, increased short-wavelength autofluorescence in the setting of diabetic macular oedema appears to be a prognostic factor for poor visual outcome, even after the resolution of the intraretinal fluid. Autofluorescence also helps in the assessment of diabetic retinal pigment epitheliopathy and choroidopathy. Fundus autofluorescence is an evolving technology that will assist in gaining further insight into the pathophysiology of diabetic retinopathy and allow for a more comprehensive evaluation of these patients.

Pathological Neurovascular Unit Mapping onto Multimodal Imaging in Diabetic Macular Edema

Diabetic retinopathy is a form of diabetic microangiopathy, and vascular hyperpermeability in the macula leads to retinal thickening and concomitant reduction of visual acuity in diabetic macular edema (DME). In this review, we discuss multimodal fundus imaging, comparing the pathogenesis and interventions. Clinicians diagnose DME using two major criteria, clinically significant macular edema by fundus examination and center-involving diabetic macular edema using optical coherence tomography (OCT), to determine the appropriate treatment. In addition to fundus photography, fluorescein angiography (FA) is a classical modality to evaluate morphological and functional changes in retinal capillaries, e.g., microaneurysms, capillary nonperfusion, and fluorescein leakage. Recently, optical coherence tomography angiography (OCTA) has allowed us to evaluate the three-dimensional structure of the retinal vasculature and newly demonstrated that lamellar capillary nonperfusion in the deep layer is associated with retinal edema. The clinical application of OCT has accelerated our understanding of various neuronal damages in DME. Retinal thickness measured by OCT enables us to quantitatively assess therapeutic effects. Sectional OCT images depict the deformation of neural tissues, e.g., cystoid macular edema, serous retinal detachment, and sponge-like retinal swelling. The disorganization of retinal inner layers (DRIL) and foveal photoreceptor damage, biomarkers of neurodegeneration, are associated with visual impairment. Fundus autofluorescence derives from the retinal pigment epithelium (RPE) and its qualitative and quantitative changes suggest that the RPE damage contributes to the neuronal changes in DME. These clinical findings on multimodal imaging help to elucidate the pathology in the neurovascular units and lead to the next generation of clinical and translational research in DME.

The Role of Intravitreal Corticosteroids in the Treatment of DME: Predictive OCT Biomarkers

This work aims to summarize predictive biomarkers to guide treatment choice in DME. Intravitreal anti-VEGF is considered the gold standard treatment for centers involving DME, while intravitreal steroid treatment has been established as a second-line treatment in DME. However, more than 1/3 of the patients do not adequately respond to anti-VEGF treatment despite up to 4-weekly injections. Not surprisingly, insufficient response to anti-VEGF therapy has been linked to low-normal VEGF levels in the serum and aqueous humor. These patients may well benefit from an early switch to intravitreal steroid treatment. In these patients, morphological biomarkers visible in OCT may predict treatment response and guide treatment decisions. Namely, the presence of a large amount of retinal and choroidal hyperreflective foci, disruption of the outer retinal layers and other signs of chronicity such as intraretinal cysts extending into the outer retina and a lower choroidal vascular index are all signs suggestive of a favorable treatment response of steroids compared to anti-VEGF. This paper summarizes predictive biomarkers in DME in order to assist individual treatment decisions in DME. These markers will help to identify DME patients who may benefit from primary dexamethasone treatment or an early switch.

Near-Infrared Confocal Reflectance Scanning Laser Ophthalmoscopy (SLO) and Short-Wavelength Autofluorescence Imaging in Cystic Diabetic Macular Edema

Objective

To characterize results of short-wavelength autofluorescent (SW-AF) and near-infrared confocal reflectance scanning laser ophthalmoscopy (NIR-cR SLO) imaging in cystic diabetic macular edema (DME).

Design

Cross-sectional study. Participants: 104 eyes from 52 naïve treatment patients with DME and mild to moderate nonproliferative diabetic retinopathy (NPDR) Methods: complete ocular examination, best-corrected visual acuity (BCVA), and imaging were performed.

Results

In NIR-cR SLO, small/medium and large-sized cysts presented with decreased and increased reflectance, respectively. In SW-AF, increased and decreased autofluorescence, corresponding to medium-/large- and small-sized cysts were noted. Mainly, the lower NIR reflectance was associated with petaloid edema pattern in SW-AF (P=0.011), BCVA (logMAR) (P=0.056), subretinal fluid (P=0.035), and the involved layers of retina by cysts (P < 0.001) in Pearson chi-square test. Fair agreement of 0.31 (P < 0.001) between NIR-cR SLO and late FA leakage was found by the weighted kappa test. In regression analysis, NIR-cR SLO abnormality is highly correlated with outer and inner nuclear layers location of the cystic changes.

Conclusions

The size of cysts and involved layers affect presenting features of SW-AF and NIR reflectance.