Analysis of Hyperreflective Dots Within the Central Fovea in Healthy Eyes Using En Face Optical Coherence Tomography

A Mathematical Model of Interstitial Fluid Flow and Retinal Tissue Deformation in Macular Edema

Purpose

This study aims to develop a mathematical model to elucidate fluid circulation in the retina, focusing on the movement of interstitial fluid (comprising water and albumin) to understand the mechanisms underlying exudative macular edema (EME).

Methods

The model integrates physiological factors such as retinal pigment epithelium (RPE) pumping, osmotic pressure gradients, and tissue deformation. It accounts for spatial variability in hydraulic conductivity (HC) across the retina and incorporates the structural role of Müller cells (MCs) in maintaining retinal stability.

Results

The model predicts that tissue deformation is maximal at the center of the fovea despite fluid exudation from blood capillaries occurring elsewhere, aligning with clinical observations. Additionally, the model suggests that spatial variability in HC across the thickness of the retina plays a protective role against fluid accumulation in the fovea.

Conclusions

Despite inherent simplifications and uncertainties in parameter values, this study represents a step toward understanding the pathophysiology of EME. The findings provide insights into the mechanisms underlying fluid dynamics in the retina and fluid accumulation in the foveal region, showing that the specific conformation of Müller cells is likely to play a key role.

Hyperreflective Dots in Central Fovea Visualized by a Novel Application of Visible-Light Optical Coherence Tomography

Visible-light optical coherence tomography (vis-OCT) is a novel noninvasive retinal imaging system that offers improved resolution compared to conventional near-infrared (NIR) OCT systems. Here, we utilized vis-OCT to produce fibergrams (vis-OCTF) for the first time in human patients, enabling en face visualization and precise quantification of hyperreflective dots in the central fovea in two patients. We also directly compare the imaging qualities of conventional vis-OCT and NIR-OCT. Vis-OCT generated a 3 × 3 mm2 en face image with an impressive axial resolution of 1.3 μm, whereas NIR-OCT produced an en face image with a larger field of view (FOV) (9 × 9 mm2) but a lower resolution of 7.0 μm. Moreover, vis-OCTF unveiled clear images of hyperreflective dots in the fovea of both patients, which were not discernible in the NIR-OCT en face images. Foveal dots have often been linked to several age-related and pathological conditions. The high-resolution images generated by vis-OCTF enable more precise characterization of changes in retinal sublayers within the central fovea.

Fingerprint sign of the Henle fibre layer in epiretinal membrane: a cross-sectional and longitudinal study

PURPOSE

To investigate the incidence and distribution of fingerprint-like microwaves in the Henle fibre layer (HFL) of the eyes with epiretinal membrane (ERM).

METHODS

Patients with idiopathic ERM were included. The fingerprint sign was defined using en-face optical coherence tomography images of the HFL, and its extent was classified into three grades.

RESULTS

At baseline, fingerprint sign was found in 70 of 83 (84.3%) eyes with ERM and was more frequently observed in eyes with a higher ERM stage (P < 0.001). Its extent increased (P < 0.001) with an increase in ERM stage or the central macular thickness (P < 0.001). Best corrected visual acuity (BCVA) was worse in eyes with a fingerprint sign than in those without (P = 0.024). Metamorphopsia was more common in eyes with a greater extent of fingerprint-like microwaves (P = 0.048). The fingerprint sign persisted over a mean follow-up period of 18.0 ± 23.3 without surgery. In 45 eyes that underwent surgery, the extent of fingerprint-like microwaves decreased at 1.2 months (P = 0.001), and further decreased at 13.7 months postoperatively (P = 0.019). However, the proportion of eyes with a fingerprint sign after surgery was similar to that observed preoperatively (P = 0.912).

CONCLUSIONS

Fingerprint-like microwaves were commonly found in eyes with ERM and were associated with ERM severity and BCVA. The microwaves remained long after surgery, although their extent may have decreased after the ERM was resolved. These results suggest that ERM traction may cause long-lasting changes in the HFL.

Presumed Müller Cell Activation in Multiple Evanescent White Dot Syndrome

Purpose

The purpose of this study was to investigate the foveal changes occurring in multiple evanescent white dot syndrome (MEWDS) using multimodal imaging techniques with a specific focus on hyper-reflective dots (HRDs).

Methods

This was a retro-prospective observational study including 35 eyes with active MEWDS. Structural and en face optical coherence tomography (OCT) was performed, with follow-up visits at 2 weeks, 6 weeks, and 2 months from baseline. HRD percentage area (HRD % area) was calculated in a 600 µm fovea centered circle on en face OCT, after background subtraction and image binarization. HRD % area was compared with 23 fellow control eyes. Longitudinal changes in the HRD % areas were assessed using repeated-measure statistics.

Results

HRDs were observed as scattered hyper-reflective spots on the vitreoretinal interface on en face OCT images, colocalizing with HRDs or vertical hyper-reflective lines on structural OCT images. The baseline evaluation showed a significantly higher HRD % area in MEWDS eyes compared to fellow eyes (0.10 ± 0.03 vs. 0.08 ± 0.04, P = 0.01). The HRD % area correlated positively with LogMAR visual acuity and inversely with the duration of symptoms. Longitudinal analysis revealed a significant reduction in the HRD % area over time. There was no significant interaction between the rate of HRD disappearance and clinical or demographic factors at baseline.

Conclusions

As HRD potentially represents the end-feet projections of activated Müller cells on the retinal surface, this study supports the involvement of Müller cells in the pathogenesis of the disease. The findings highlight the potential of en face OCT imaging for monitoring the progression of MEWDS.

Long-term assessment of internal limiting membrane peeling for full-thickness macular hole using en face adaptive optics and conventional optical coherence tomography

OBJECTIVE

To evaluate the long-term structural and microvascular retinal effects of internal limiting membrane peeling for full-thickness macular hole (FTMH) using en face adaptive optics optical coherence tomography (AO-OCT), conventional OCT, and OCT angiography (OCTA).

DESIGN

Interventional case series.

PARTICIPANTS

Patients with FTMH treated with vitrectomy, internal limiting membrane peeling, and gas tamponade.

METHODS

Eleven eyes with FTMH that had at least 12 months of postoperative follow-up were enrolled in the study. En face AO-OCT was used to image the superficial retina in the peeled and nonpeeled areas. En face structural OCT was performed to image the inner retinal dimples (IRDs), macular thickness, and retinal nerve fibre layer (RNFL). En face OCTA was used to examine the integrity of the peripapillary nerve fibre layer (NFL) plexus.

RESULTS

AO-OCT showed RFNL wrapping around the IRDs, and no obvious peripapillary NFL plexus dropout was seen with OCTA. Scattered hyper-reflective dots were observed on the surface of the peeled retina in all patients imaged with AO-OCT. No significant differences were found in IRD number (91.5 ± 24.4 versus 77.2 ± 14.7; P = 2.07), IRD proportionate area (8.36 ± 3.34 versus 7.53 ± 2.60; P = 0.159), or macular thickness between the 6- and 12-month (or greater) postoperative visits.

CONCLUSION

IRDs do not to progress beyond 6 months postoperatively, and no obvious damage to RFNL and peripapillary NFL plexus was detected. Hyper-reflective dots on the surface of the retina suggestive of possible Müller cell reactive gliosis were identified with AO-OCT.

En Face OCT Detects Preretinal Abnormal Tissues Before and After Internal Limiting Membrane Peeling in Eyes with Macular Hole

PURPOSE

To assess preretinal abnormal tissue (PAT) using en face OCT in eyes with idiopathic macular holes (MHs).

DESIGN

Retrospective, observational study.

PARTICIPANTS

Patients with MH who received 6 × 6-mm spectral-domain-OCT scans.

METHODS

Preretinal abnormal tissue was detected by en face OCT images with a custom slab, defined with an anterior boundary of 6 μm anterior to the internal limiting membrane (ILM) and a posterior boundary at 3 μm posterior to the ILM. The PAT was defined as any abnormal tissues observed in en face OCT.

MAIN OUTCOME MEASURES

Characteristics of preoperative and postoperative PAT.

RESULTS

Sixty eyes with MH from 60 patients were included. Fifty-one eyes underwent preoperative analysis, and 46 eyes underwent postoperative examination. Before surgery, 48 (94%) eyes had a mean (standard deviation [SD]) PAT of 6.6 (9.8) mm². The corresponding cross-sectional OCT showed PAT consisting of epiretinal proliferation, epivascular glia, and a preretinal hyperreflective band. Preretinal abnormal tissue was contiguous to the hole (peri-MH PAT) in 12 eyes (24%), whereas others (36 eyes, 76%) had a scattered distribution (extrafoveal PAT). The area of PAT was greater in eyes with a peri-MH PAT than in eyes with an extrafoveal PAT (P < 0.0001). Compared to the eyes with the extrafoveal PAT, the eyes with the peri-MH PAT were associated with men (P = 0.0059) and worse baseline visual acuity (VA) (P = 0.0002). In eyes with ILM peeling (42 eyes), postoperative PAT proliferation was observed from the edge of the ILM peeling toward the periphery over a 1-year follow-up. The mean (SD) area of PAT at 2 weeks after surgery was 3.4 (3.6) mm² and increased to 12.1 (6.4) mm² at 12 months (P < 0.0001). However, no PAT increase was observed in 4 eyes that underwent vitrectomy without ILM peeling. The postoperative PAT size was not associated with the postoperative VA.

CONCLUSIONS

En face OCT revealed PAT in most eyes with MHs. Peri-MH PAT was associated with worse VA and was seen more frequently in male patients. Postoperative PAT proliferation may be triggered by ILM peeling, but it is not associated with worse VA.

Imaging biomarkers of leukaemic choroidopathy

PURPOSE

To longitudinally investigate choroidal and choriocapillaris perfusion metrics and the number of choroidal hyperreflective foci (HRF) in patients with acute leukaemia (AL) before and after disease remission and to correlate these metrics with systemic parameters during active disease.

METHODS

Prospective, longitudinal study of 26 eyes of 14 AL patients. All patients underwent optical coherence tomography (OCT) and OCT-angiography (OCTA) in the acute phase. Subfoveal choroidal thickness (CT), total, luminal and stromal choroidal area (TCA, LCA, SCA), choroidal vascularity index (CVI), choriocapillaris flow deficits (cFD) density, and choroidal HRF number were computed. In a subset, the measurements were repeated after AL remission. Age- and gender-matched 26 healthy controls were recruited for cross-sectional comparisons.

RESULTS

Patient's mean age was 59 ± 12 years. The TCA, LCA, SCA and choroidal HRF number were significantly higher in patients than controls (p = 0.028, p = 0.044, p = 0.024 and p = 0.001, respectively). Lower haemoglobin levels were associated with lower CT (r = 0.58, p = 0.008). Higher D-dimer values were associated with lower TCA (r = -0.52, p = 0.008), lower LCA (r = -0.50, p = 0.006), higher cFD density (r = 0.41, p = 0.044) and higher choroidal HRF number (r = 0.47, p = 0.008). The CT, TCA, SCA and choroidal HRF number significantly reduced after AL remission (p = 0.001, p = 0.047, p = 0.007 and p = 0.002 respectively). The CVI increased significantly compared to the active phase (p = 0.013).

CONCLUSION

The study demonstrates a subclinical choroidal involvement in patients with AL, with relative stromal thickening in the acute phase, and normalization after disease remission. Choroidal HRF were identified as a biomarker of leukaemic choroidopathy. Choriocapillaris and choroidal vascularity were inversely correlated with a systemic pro-coagulant state.

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.

En Face Optical Coherence Tomography Imaging of Foveal Dots in Eyes With Posterior Vitreous Detachment or Internal Limiting Membrane Peeling

Purpose

To analyze the morphology of foveal hyperreflective dots (HRD) identified with en face optical coherence tomography (OCT) and evaluate the effects of internal limiting membrane (ILM) peeling and posterior vitreous detachment (PVD) on the number of these lesions.

Methods

Retrospective cross-sectional study of patients with OCT angiography and en face OCT. Using en face OCT, superficial HRD lying on the foveal floor were measured and quantitated in eyes with ILM peel and in the fellow nonsurgical eyes. Eyes with foveal PVD were also compared to fellow eyes without foveal PVD. High-magnification en face OCT was also performed to better understand the morphology of HRD in the fovea.

Results

Eyes that underwent ILM peel (n = 10) displayed fewer HRD (P = 0.012) compared to control fellow nonoperated eyes. In eyes with foveal PVD, the mean number of HRD was numerically greater, but without statistical significance, compared to the contralateral eye without foveal PVD. High-magnification en face OCT illustrated HRD with irregular shapes and fine cilia-like or dendriform extensions. Average length of HRD was between 15 to 21 µm in all four groups.

Conclusions

HRD decreased in eyes with ILM peeling by en face OCT compared with fellow nonoperated eyes and exhibited a glial cell-like morphology and size closely resembling the white dot fovea described previously using scanning electron microscopy. HRD may represent processes of activated retinal glia, possibly Muller cells, that traverse defects in the ILM.