Imaging of Epiretinal Membranes Using En Face Widefield Swept-Source Optical Coherence Tomography

Correlation between retinal sensitivity and retinal vascular perfusion after idiopathic epiretinal membrane peeling

BACKGROUND

To evaluate the correlations between anatomical and functional changes after idiopathic epiretinal membrane (iERM) surgery.

METHODS

In this prospective, observational, single-center study, consecutive patients who underwent iERM peeling were enrolled. Reported data were pre- and postoperative best-corrected visual acuity (BCVA), retinal sensitivity (RS) and fixation stability values on microperimetry, structural macular features on SD-OCT and OCTA. RS of foveal and parafoveal area was analysed and two sub-groups were identified whether RS improved or remained unchanged/worsened after surgery; consequently, vascular perfusion density (VPD) of the same area was studied.

RESULTS

Twenty-nine eyes of 29 patients were examined. The post-operative improvement in terms of BCVA, RS and fixation within the central 4 degrees was significant (p < 0.001, p < 0.001, p = 0.001), as well as the foveal thickness and macular volume change/reduction (p < 0.001). The pre-operative superficial VPD, choriocapillaris VPD and capillary free zone (CFZ) area were significantly reduced compared to the fellow healthy eye (p = 0.001, p = 0.02, p < 0.001). Choriocapillaris VPD showed a statistically significant increase after surgery (p < 0.02). Superficial, deep and choriocapillaris VPD of the improved RS group showed a significant increase both in foveal (p = 0.03, p = 0.03, p = 0.01) and parafoveal areas (p = 0.01, p = 0.03, p = 0.001).

CONCLUSIONS

We reported a higher VPD in the retinal area that experienced a retinal sensitivity improvement 6 months after ERM surgery. This result objectifies the tight bond between visual function and retinal perfusion in ERM patients.

Detection of neovascularisation in the vitreoretinal interface slab using widefield swept-source optical coherence tomography angiography in diabetic retinopathy

AIMS

To compare the efficacy of diabetic retinal neovascularisation (NV) detection using the widefield swept-source optical coherence tomography angiography (WF SS-OCTA) vitreoretinal interface (VRI) Angio slab and SS-OCT VRI Structure slab.

METHODS

A prospective, observational study was performed at Massachusetts Eye and Ear from January 2019 to June 2020. Patients with proliferative diabetic retinopathy (PDR), patients with non-proliferative diabetic retinopathy and patients with diabetes but without diabetic retinopathy were included. All patients were imaged with WF SS-OCTA using the 12×12 mm Angio scan protocol centred on the fovea and optic disc. The en-face SS-OCTA VRI Angio slab and SS-OCT VRI Structure slab were evaluated for the presence or absence of NV. SS-OCTA B-scan was used to classify NV according to cross-sectional morphology (forward, tabletop or flat). All statistical analyses were performed using SPSS V.26.0.

RESULTS

One hundred and forty-two eyes of 89 participants were included in the study. VRI Angio detected NV at higher rates compared with VRI Structure (p<0.05). Combining VRI Angio and Structure improved detection rates compared with VRI Angio alone (p<0.05). Due to segmentation errors of the internal limiting membrane, NV with flat morphological classification had lower rates of detection on VRI Angio compared with NV with forward and tabletop morphology (p<0.05).

CONCLUSIONS

WF SS-OCTA 12×12 mm VRI Angio and SS-OCT VRI Structure imaging centred on the fovea and optic disc detected NV with high sensitivity and low false positives. The VRI slab may be useful to diagnose and monitor PDR in clinical practice.

Identification and Characterization of Epivascular Glia Using En Face Optical Coherence Tomography

PURPOSE

The purpose of this study was to describe the clinical features of epivascular glia (EVG) using en face optical coherence tomography (OCT).

DESIGN

Retrospective cross-sectional study.

METHODS

Single-institution en face OCT images were reviewed. Eyes displaying EVG were captured with manual internal limiting membrane (ILM) segmentation and analyzed with customized segmentation . A random age- and sex-matched control group was selected to determine relative epiretinal membrane (ERM) prevalence.

RESULTS

Characteristic hyper-reflective ILM plaques with dendrite-like radiations were identified using en face OCT and displayed vascular predilection. A total of 161 eyes with EVG (the EVG group) and 2,315 eyes without EVG (control group) were identified from a total cohort of 1,298 patients (or 2,476 eyes). The prevalence of EVG was 161 of 2,476 eyes (6.5%) and 119 of 1,298 patients (9.2%) in the cohort. Mean age was 79.3 ± 10.7 years old in the EVG group and 55.9 ± 24.6 years old in the control group (P <.001). An advanced posterior vitreous detachment (PVD) stage was more common in the EVG group (grade 3: 41.7%; grade 4: 48.6%) than in the control group (grade 3: 18.5%; grade 4: 26.9%; P <.001). Contractile ERM was present in 71 of 161 eyes (44.1%) with EVG compared to 30 of 161 eyes (18.6%) in a random age- and sex-matched control cohort without EVG (P <.001).

CONCLUSIONS

EVG previously described with histopathology and scanning electron microscopy can be identified using en face OCT. In this study, these lesions were associated with older age, pseudophakia, and advanced PVD, supporting the role of Müller cell activation through ILM breaks triggered by PVD, a pathogenic mechanism proposed by previous studies.

Swept-Source OCT En Face Imaging of Paravascular Inner Retinal Defects

Widefield swept-source optical coherence tomography angiography (SS-OCTA) was performed on eyes with paravascular inner retinal defects (PIRDs) and the morphological alterations of PIRDs were described. Patients with PIRDs were imaged using 12 mm × 12 mm SS-OCTA scans. En face structural and angiographic images of the superficial retinal layers were reviewed along with retinal thickness maps. SS-OCTA en face structural images identified dark, scalloped regions along major retinal veins that corresponded to PIRDs on B-scans. The authors concluded that imaging with both structural and angiographic en face OCT was useful for the diagnosis and monitoring of patients with PIRDs. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:407-411.].

Early Vascular and Functional Changes after Vitreoretinal Surgery: A Comparison between the Macular Hole and Epiretinal Membrane

(1) Background: The aim of this observational comparative study was to investigate early retinal vascular and functional changes in patients undergoing vitreoretinal surgery for idiopathic epiretinal membrane (iERM) or macular hole (MH) using a widefield swept-source optical coherence tomography angiography (WSS-OCTA). (2) Methods: Forty one diseased eyes were enrolled in the study. Twenty three eyes with iERM diagnosis (ERM group) underwent 25-gauge vitrectomy with inner limiting membrane (ILM) and MER peeling, while eighteen eyes with MH (MH group) underwent 25-gauge vitrectomy with inverted flap technique. Functional and anatomical/perfusion parameters were evaluated pre- and postoperatively in all eyes by means of WSS-OCTA system, microperimetry (MP3), best corrected visual acuity assessment, central macular thickness (CMT) and MH diameter calculation. For each eye, 12 × 12 mm OCTA volume scans were acquired by a retinal specialist and a semi-automated algorithm was used for a quantitative vessel analysis of the superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris (CC). In detail, perfusion density (PD) of the SCP, DCP and CC was evaluated in four circles (one central in the macular area of 5 mm diameter; three midperiphery circles (temporal, superior and inferior) of 3 mm). In addition, the vessel length density (VLD) of the SCP and DCP for the same circles was quantified. (3) Results: In the MH group, PD of the SCP significantly increased in the macular area (p = 0.018) and in the superior ring (p = 0.016); PD of the DCP significantly increased in the macular area (p = 0.015) and in the superior and inferior ring (p = 0.016) 3 months after surgery. In the ERM group, PD of the SCP and DCP significantly increased in the macular area and superior ring, respectively (p = 0.001; p = 0.032), 3 months after surgery. During follow-up there was a significant improvement in terms of functional (Best corrected visual acuity, p = 0.007 and p = 0.029; microperimetry ((MP3) 10°, p = 0.003 and p = 0.004; MP3 2°, p = 0.028 and p = 0.003 in MH group and ERM group respectively) and anatomical parameters (CMT, p = 0.049 in ERM group; hole complete closure in MH group). (4) Conclusions: After vitreoretinal surgery, early retinal vascular and functional changes can be promptly observed and quantified to monitor and potentially predict surgery outcomes. Widefield OCTA devices allow for a detailed microvasculature analysis of retina and choriocapillaris in the macular area and in the periphery, showing a different behaviour of retinal sectors in two distinct vitreoretinal disorders.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Early retinal flow changes after vitreoretinal surgery in idiopathic epiretinal membrane using swept source optical coherence tomography angiography

(1) Background: The aim of this observational cross-sectional work was to investigate early retinal vascular changes in patients undergoing idiopathic epiretinal membrane (iERM) surgery using swept source optical coherence tomography angiography (SS-OCTA); (2) Methods: 24 eyes of 24 patients who underwent vitrectomy with internal limiting membrane (ILM) peeling were evaluated pre- and postoperatively using SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). For each eye, five 6x6-mm OCTA volume scans were acquired by two observers independently. The en face images of superficial capillary plexus (SCP) were then exported to imageJ and a semi-automated algorithm was used for subsequent quantitative analysis. Perfusion density (PD), vessel length density (VLD), vessel diameter index (VDI) and vessel tortuosity (VT) of SCP were evaluated in both the parafoveal (2.5 mm diameter) and perifoveal areas (5.5 mm diameter); (3) Results: At OCTA analysis statistically significant differences were found between controls and diseased eyes for all parameters in parafoveal and perifoveal regions (p < 0.001; p < 0.05) except for perifoveal VLD. During 6-month follow up, both anatomical/perfusion and functional parameters showed a statistically significant improvement if compared to preoperative values. In detail, at one-month post vitrectomy, VLD and VT significantly changed in parafoveal region (p = 0.043; p = 0.045), while PD and VDI showed a trend of increase in both parafoveal and perifoveal region. At 6 months after surgery, PD, VLD and VT of parafoveal region significantly improved (p = 0.021, p = 0.018, p = 0.047 respectively). (4) Conclusions: SS-OCTA provides a quantitative and qualitative analysis of the superficial capillary plexus allowing for early vascular changes assessment after vitrectomy with iERM and ILM peeling.