Hyperreflective cystoid spaces in diabetic macular oedema: prevalence and clinical implications

Ultrastructural imaging biomarkers in diabetic macular edema: A major review

Diabetic macular edema (DME) is a vision-threatening complication of diabetic retinopathy and causes significant morbidity in patients. Anti-vascular endothelial growth factor (VEGF) agents are the mainstay of treatment for DME, with steroid implants being used for the treatment of anti-VEGF resistant eyes. Over the years, several classification systems have been devised to describe the patterns of DME using optical coherence tomography (OCT). With the advent of effective treatments, it has become imperative that imaging cues are not merely used for classifying the disease but also as biomarkers for prognostication of disease activity and treatment response. In this aspect, newer imaging findings such as hyperreflective dots, photoreceptor integrity, and disorganization of retinal inner layers have been characterized in detail by several authors. Macular perfusion analysis using OCT angiography is the latest in the armamentarium for imaging DME. In this narrative review, we have summarized all relevant literature related to the ultrastructural imaging-based biomarkers of DME and their correlation to treatment.

Spectral-domain OCT characteristics of intraretinal hyper-reflective foci associated with age-related macular degeneration and diabetic retinopathy

OBJECTIVE

The purpose of this study was to quantitatively analyze and compare OCT characteristics of intraretinal hyper-reflective foci (IHRF) in eyes with diabetic retinopathy (DR) versus age-related macular degeneration (AMD).

DESIGN

a retrospective observational study.

PARTICIPANTS

54 treatment-naïve eyes (27 DR and 27 AMD).

METHODS

The IHRF lesions in OCT B-scan were semi-automatically segmented. Mean reflectivity (MR), maximum diameter, circularity index (Cir), area, and the angle between the greatest linear dimension (GLD) and the horizontal were computed for each IHRF lesion. The presence and absence of a posterior shadow and the axial location were assessed. The MR was normalized using the vitreous and nerve fiber layer reflectance as dark and bright reference standards, respectively.

RESULTS

A total of 1149 IHRF (1051 in DR and 98 in the AMD group) were identified, with a mean of 39 ± 36 lesions in DR eyes compared to only 4 ± 4 in AMD eyes (p < 0.001). The mean area of individual IHRF lesions was greater in DR eyes (1305 ± 1647 μm² vs 1031 ± 750 μm²; p = 0.016), but IHRF in AMD eyes had higher reflectivity (1.17 ± 0.14 vs 1.03 ± 0.17; p < 0.001). The angle of the GLD relative to the horizontal was greater in AMD eyes, indicating that IHRF in AMD eyes were more horizontally oriented. In AMD eyes, 88.8% of IHRF were located beneath the inner border of the outer nuclear layer (ONL), while in DR eyes, 56.9% were located there (p < 0.001).

CONCLUSIONS

IHRF lesions in eyes with DR and AMD demonstrate significant differences, with IHRF in DR eyes tending to be larger and less hyper-reflective compared to AMD eyes.

Electrodiagnostic Biomarkers in Paraneoplastic Retinopathy

OBJECTIVE

Paraneoplastic retinopathy (PNR) is a rapid-onset photoreceptor and post-photoreceptor dysfunction triggered by a cross-reaction between antigens expressed by the underlying tumour and retinal proteins. The present study aims to determine the electrodiagnostic biomarkers that support the diagnosis of PNR and evaluate the effect of treatment.

METHODS

A retrospective observational case-controlled study including 25 patients with suspected PNR, of which 11 patients were diagnosed with PNR. The presence of PNR was confirmed based on clinical examination, supported by colour fundus photography, fundus autofluorescence imaging, optical coherence tomography, fluorescein angiography, retinal vessel oximetry, colour test, full-field electroretinogram (ffERG), on-/off ERG, S-cone ERG, and multifocal ERG (mfERG). The relationships between the clinical symptomatology and the effect of therapy were evaluated.

RESULTS

All PNR patients (Nr: 11) presented with subjective symptoms of newly reported central vision or visual field deterioration. Posterior segment findings showed a severe patchy-like retinal atrophy, attenuation of the retinal vessels, and a waxy optic disc. Optical coherence tomography revealed a discontinued ISe line, and multiple hyperreflective foci. Retinal vessel oxygen saturation was increased. Multifocal ERG revealed reduced central and paracentral responses and ffERG severely attenuated scotopic-, photopic-, on-/off- and S-cone responses. The colour vision test revealed a tritan-tetartan-weakness. Two of the PNR patients underwent rituximab therapy with no further progression and even recovery of electrodiagnostic responses.In 1 nPNR (non-paraneoplastic retinopathy) patient (total Nr: 14) pseudoxanthoma elasticum-related retinopathy was the reason for impaired vision. In 3 of 13 patients with bronchopulmonary cancer a MEK- and FGFR-inhibitor- drug toxicity was the reason for the visual deterioration.

CONCLUSION

Careful investigation for signs of central and/or peripheral visual field deterioration must be performed in the presence of history of a co-existing malignancy. The possibility of PNR should be taken into account. The electrodiagnostic biomarkers, suggested in this study, may help to promptly recognise PNR and also to evaluate the effect of implemented therapy.

The Presence of Hyperreflective Foci Reflects Vascular, Morphologic and Metabolic Alterations in Retinitis Pigmentosa

Background: The presence of hyperreflective foci (HRF) in retinitis pigmentosa (RP) is a potentially new finding. We investigated the presence of HRF in SD-OCT images in eyes with RP and its relation to vascular, morphologic and metabolic findings in RP. Methods: The study was performed on 42 RP patients and 24 controls. Using SD-OCT, we calculated the amount of HRF within the entire retina (HRF-ER) and the outer nuclear layer (HRF-ONL). Retinal vessel diameters (μm) and oxygen saturation (%) values were measured using Oxymap T1. We evaluated the mean diameter in retinal arterioles (D-A) and venules (D-V), the corresponding oxygen saturation values (A-SO₂, V-SO₂) and the oxygen saturation difference (A-V SO₂). Results: RP differed from controls by HRF-ER, HRF-ON and EZ-length (p < 0.001). D-A and D-V were narrower and A-SO₂ and V-SO₂ were higher in RP (p ≤ 0.001). Within RP, significant interactions were found between the HRF-ER* group and: BCVA, EZ length, D-A, A-SO₂ and A-V SO₂ (p ≤ 0.018). The HRF-ONL* group interactions were significant for: BCVA, EZ length, D-A, A-SO₂ and A-V SO₂ (p ≤ 0.014). Conclusion: The present study highlights the presence of HRF to reflect the vascular, morphologic and metabolic alterations in RP. These biomarkers seem to be associated with remodeling and apoptosis that occur with the progression of degeneration.

Significance of Hyperreflective Foci as an Optical Coherence Tomography Biomarker in Retinal Diseases: Characterization and Clinical Implications

Hyperreflective foci (HRF) is a term coined to depict hyperreflective dots or roundish lesions within retinal layers visualized through optical coherence tomography (OCT). Histopathological correlates of HRF are not univocal, spacing from migrating retinal pigment epithelium cells, lipid-laden macrophages, microglial cells, and extravasated proteinaceous or lipid material. Despite this, HRF can be considered OCT biomarkers for disease progression, treatment response, and prognosis in several retinal diseases, including diabetic macular edema, age-related macular degeneration (AMD), retinal vascular occlusions, and inherited retinal dystrophies. The structural features and topographic location of HRF guide the interpretation of their significance in different pathological conditions. The presence of HRF less than 30 μm with reflectivity comparable to the retinal nerve fiber layer in the absence of posterior shadowing in diabetic macular edema indicates an inflammatory phenotype with a better response to steroidal treatment. In AMD, HRF overlying drusen are associated with the development of macular neovascularization, while parafoveal drusen and HRF predispose to macular atrophy. Thus, HRF can be considered a key biomarker in several common retinal diseases. Their recognition and critical interpretation via multimodal imaging are vital to support clinical strategies and management.