Multimodal Imaging Features and Clinical Relevance of Subretinal Lipid Globules

Non-exudative OCT findings in neovascular AMD

In this narrative review we describe the main optical coherence tomography biomarkers appearing in eyes with neovascular age-related macular degeneration (AMD) that do not directly correspond to exudation. We highlight those signs that may mimic exudation and therefore do not require active treatment, such as outer retinal tubulations, pseudocysts, lipid globules, or hyporeflective wedges. Other signs may indicate impending exudation such as hyperreflective foci or shallow irregular retinal pigment epithelium elevation, and therefore should be carefully monitored. We also review and summarize the different origins of subretinal hyperreflective material and describe the main signs of degeneration seen in eyes with AMD, such as outer retinal tubulation, thinning of the retinal layers, outer retinal atrophy, and choroidal changes.

Subretinal transient hyporeflectivity in neovascular age-related macular degeneration and its response to a loading phase of aflibercept: PRECISE report 4

PURPOSE

To describe the prevalence of subretinal transient hyporeflectivity (STHR) in exudative neovascular age-related macular degeneration (nAMD) and its response to a loading phase of aflibercept.

METHODS

Optical coherence tomography (OCT) scans of treatment-naïve nAMD patients captured at baseline and after a loading phase of aflibercept were graded for presence of STHR, defined as a small, well-defined, round, subretinal, hyporeflective area, delimited between the ellipsoid zone (EZ) and the retinal pigmented epithelium/Bruch membrane complex. OCT parameters recorded were macular neovascularisation (MNV) subtypes, location of retinal fluids (subretinal fluid, SRF and intraretinal fluid, IRF), central retinal and choroidal thickness. Response was defined as absence of IRF and SRF. Factors associated with completely resolved STHR versus persistent STHR post-loading phase were compared.

RESULTS

2039 eyes of 1901 patients were analysed. STHR was observed in 79 eyes of 78 patients, with an estimated prevalence of 3.87% (95% CI 3.08-4.81%). STHR were seen in 44 type 1 MNV (56%), 27 with type 2 (34%), and 8 with type 3 (10%). At baseline, a total of 303 STHR were present, ranging between 1-22 per eye. The total number of STHR reduced significantly after the loading phase to 173 (p = 0.002). Complete disappearance of STHR was seen in 44 eyes (56%) and persistent STHR in the rest (44%).

CONCLUSIONS

STHR may represent a marker of low-grade exudation in nAMD eyes with good response to a loading phase of aflibercept. However, its potential role as an independent nAMD activity biomarker is limited as most resolve after the loading phase.

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.

Subretinal hyporeflective globule: A novel OCT finding in central serous chorioretinopathy

PURPOSE

To describe the subretinal hyporeflective globule in cases of central serous chorioretinopathy (CSC).

METHODS

A retrospective analysis of consecutive cases of CSC presenting to a tertiary eye care center in eastern India was conducted. Subretinal hyporeflective globules were identified as small globular lesions below the external limiting membrane/ellipsoid zone, but above the RPE layer. They had a hyperreflective border with a hyporeflective core and a clear posterior tail of hyper-transmission.

RESULTS

The present study analyzed 137 eyes of 137 patients. Eighty (58.4%) eyes had acute disease at presentation, 48 (35%) eyes had chronic disease, and eight (5.8%) eyes had resolved CSC. Subretinal hyporeflective globules were seen in 27 (21.8%) eyes, of which choroidal caverns were seen in seven (5.1%) eyes. Twenty-five eyes with chronic CSC and only two eyes with acute CSC had subretinal hyporeflective globules. Three eyes with resolved CSC had subretinal hyporeflective globules.

CONCLUSION

We describe subretinal hyporeflective globule as a novel optical coherence tomography (OCT) finding in cases of CSC and describe its clinical correlates.

Optical coherence tomography biomarkers in early and intermediate age-related macular degeneration: A clinical guide

Advanced forms of age-related macular degeneration (AMD), characterised by atrophic and neovascular changes, are a leading cause of vision loss in the elderly population worldwide. Prior to the development of advanced AMD, a myriad of risk factors from the early and intermediate stages of AMD have been published in the scientific literature over the last years. The ability to precisely recognise structural and anatomical changes in the ageing macula, altogether with the understanding of the individual risk implications of each one of them is key for an accurate and personalised diagnostic assessment. The present review aims to summarise updated evidence of the relative risk conferred by diverse macular signs, commonly seen on optical coherence tomography, in terms of progression to geographic atrophy or macular neovascularization. This information may also serve as a basis for tailored follow-up monitoring visits.

SUBRETINAL LIPID GLOBULES AN EARLY BIOMARKER OF MACULAR NEOVASCULARIZATION IN EYES WITH INTERMEDIATE AGE-RELATED MACULAR DEGENERATION

PURPOSE

To explore the association between subretinal lipid globules (SLGs) detected in eyes with intermediate age-related macular degeneration with the presence of nonexudative macular neovascularization.

METHODS

This was a retrospective analysis of 113 consecutive patients with bilateral intermediate age-related macular degeneration (226 eyes) followed for a least 6 months. All eyes underwent multimodal imaging with fundus autofluorescence, spectral-domain optical coherence tomography, and optical coherence tomography angiography. Subretinal lipid globules were identified on spectral-domain optical coherence tomography as round hyporeflective lesions measuring 31 to 157 µ m located between the ellipsoid zone and the retinal pigment epithelium/Bruch membrane complex. Nonexudative macular neovascularization was detected with optical coherence tomography angiography. The features of NE-MNV lesions detected in eyes with SLGs were compared with those in eyes without SLGs.

RESULTS

Subretinal lipid globules were identified in 15 eyes of which 14 eyes (93.3%) demonstrated NE-MNV on optical coherence tomography angiography. In the remaining 98 eyes without SLGs, 18 (18.4%) displayed NE-AMD on optical coherence tomography angiography. The macular neovascularization area was larger in the SLG subgroup (+0.38 vs. +0.21 mm 2 , P = 0.008) and showed faster horizontal growth (+727 µ m, CI 95% 250.4, 1,205.4) than MNV in eyes without SLGs (+64.9 µ m, CI 95%, 24.3, 154) on optical coherence tomography B-scans. After a mean of 11.6 months, the conversion rate to exudative MNV was similar between eyes with SLGs and those without SLGs [8/26 (38.5%) versus 3/13 (27.3%), P = 0.56)].

CONCLUSION

The detection of SLGs in eyes with intermediate age-related macular degeneration was strongly correlated with the presence of NE-MNV. Although these MNV lesions were larger and grew faster than NE-MNV detected in eyes lacking SLGs, the rates of conversion to exudative MNV appeared similar.

Quantitative multimodal imaging of extensive macular atrophy with pseudodrusen and geographic atrophy with diffuse trickling pattern

To compare clinical and imaging characteristics of extensive macular atrophy with pseudodrusen-like appearance (EMAP) versus diffuse-trickling geographic atrophy (DTGA) and non-diffuse-trickling geographic atrophy (nDTGA) phenotypes of age-related macular degeneration. Prospective, observational study performed in the Ophthalmology Department of IRCCS San Raffaele Hospital between January 2015 and January 2021. Patients examination included fundus autofluorescence (FAF) and optical coherence tomography at baseline and follow-up visits. We measured subfoveal choroidal thickness (SCT), Sattler/choroid ratio (SCR), choroidal vascularity index and ellipsoid zone disruption distance on OCT scans. We calculated progression rates and circularity of the atrophic lesions on FAF images. These variables were compared between the three groups and correlations with progression rates and visual acuity were assessed. Sixty-three eyes from 63 patients were included: 18 with EMAP, 18 with DTGA and 27 with nDTGA. Mean follow-up was 3.73 ± 2.12 years. EMAP and DTGA shared a faster progression, lower circularity and SCR, and higher EZ disruption distance than nDTGA, while SCT and CVI were similar between the three groups. Baseline circularity and SCR correlated with progression rates. EMAP and DTGA show similar OCT and FAF characteristics, which differ from nDTGA.

MULTIMODAL IMAGING OF A CHOROIDAL NEVUS WITH CAVERNS IN THE SETTING OF PACHYCHOROID DISEASE

PURPOSE

To describe the multimodal imaging findings of extensive choroidal caverns within a choroidal nevus in an eye with pachychoroid spectrum disease.

METHODS

A 69-year-old woman was referred with a known history of branch retinal vein occlusion in the right eye and choroidal nevus in the left eye. Fundus examination of both eyes revealed subretinal yellow deposits, suggestive of pachydrusen. Retinal venous collaterals were noted in the temporal macular of the right eye. A lightly pigmented choroidal lesion with nearly confluent overlying drusen and retinal pigment epithelial alterations, consistent with chronic choroidal nevus, was noted in the macula of the left eye.

RESULTS

Optical coherence tomography B-scans revealed thickened choroid (pachychoroid) with subfoveal choroidal thickness of 504 µ m and 580 µ m with large hyporeflective spaces suggestive of pachyvessels in both eyes. In the region of the choroidal nevus, the choroidal vascular spaces appeared comparatively large and were classified as "caverns" measuring up to 480 µ m in diameter. Optical coherence tomography angiography and indocyanine green angiography demonstrated the absence of flow within the caverns. Indocyanine green angiography further illustrated choroidal vascular hyperpermeability with patchy hyperfluorescent areas in both eyes. Wide-field swept-source optical coherence tomography showed mild posterior scleral bowing, a feature occasionally documented with choroidal nevus, and highlighted greater hyporeflectivity and hypertransmission on optical coherence tomography within the caverns compared with the noncavernous choroidal vessels.

CONCLUSION

Choroidal caverns can occur within choroidal nevus in the setting of pachychoroid disease.

SUBRETINAL TRANSIENT HYPOREFLECTIVITY IN AGE-RELATED MACULAR DEGENERATION: A Spectral Domain Optical Coherence Tomography Study

PURPOSE

To describe and assess the prognostic significance of subretinal transient hyporeflectivity (STHR) on a novel spectral domain optical coherence tomography (SD-OCT) in age-related macular degeneration.

METHODS

Consecutive patients with age-related macular degeneration (AMD) presenting STHR, defined as a small, well-defined, round subretinal, hyporeflective lesion, on SD-OCT and without exudative signs were included. Clinical examination and SD-OCT (SPECTRALIS, Heidelberg Engineering, Heidelberg, Germany) were analyzed at inclusion, 1 month before inclusion, and until the onset of exudative signs during the 12-month follow-up.

RESULTS

Thirty-five STHR in 21 eyes of 20 patients were included. Among the 21 eyes, 2 eyes had early AMD, 1 eye had nonexudative asymptomatic macular neovascularization, and 18 eyes presented late AMD: 17 eyes neovascular AMD and 1 eye geographic atrophy. During the 2-month follow-up, 97.1% (34/35) of STHR disappeared. During the 12-month follow-up, 57.1% of eyes (12/21) developed exudative signs on 1 eye with early AMD and 11 eyes with neovascular AMD.

CONCLUSION

Subretinal transient hyporeflectivity is a novel SD-OCT sign in patients with AMD. The eyes with isolated STHR should be closely monitored on a monthly basis to detect further exudation.

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.

OCT Biomarkers in Neovascular Age-Related Macular Degeneration: A Narrative Review

Age-related macular degeneration (AMD) is the leading cause of legal blindness in elderly people. Neovascular AMD (nAMD) is responsible for the majority of cases of severe visual loss in eyes with AMD. Optical coherence tomography (OCT) is the most widely used technology for the diagnosis and follow-up of nAMD patients, which is widely used to study and guide the clinical approach, as well as to predict and evaluate treatment response. The aim of this review is to describe and analyze various structural OCT-based biomarkers, which have practical value during both initial assessment and treatment follow-up of nAMD patients. While central retinal thickness has been the most common and one of the first OCT identified biomarkers, today, other qualitative and quantitative biomarkers provide novel insight into disease activity and offer superior prognostic value and better guidance for tailored therapeutic management. The key importance of retinal fluid compartmentalization (intraretinal fluid, subretinal fluid, and subretinal pigment epithelium (RPE) fluid) will be discussed firstly. In the second part, the structural alterations of different retinal layers in various stages of the disease (photoreceptors layer integrity, hyperreflective dots, outer retinal tubulations, subretinal hyperreflective material, and retinal pigment epithelial tears) will be analyzed in detail. The last part of the review will focus on how alterations of the vitreoretinal interface (vitreomacular adhesion and traction) and of the choroid (sub-RPE hyperreflective columns, prechoroidal clefts, choroidal caverns, choroidal thickness and choroidal volume, and choroidal vascular index) interact with nAMD progression. OCT technology is evolving very quickly, and new retinal biomarkers are continuously described. This up-to-date review article provides a comprehensive description on how structural OCT-based biomarkers provide a valuable tool to monitor the progression of the disease and the treatment response in nAMD patients. Thus, in this perspective, clinicians will be able to allocate hospital resources in the best possible way and tailor treatment to the individual patient's needs.