White dot fovea

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.

DESCRIBING THE LOCATION AND MORPHOLOGY OF THE DOTS IN WHITE DOT FOVEA USING ADAPTIVE OPTICS

PURPOSE

To characterize the white dots in white dot fovea, an entity chiefly described in Japan, using adaptive optics imaging and propose a hypothesis regarding their origin.

METHOD

The patient underwent comprehensive ophthalmic examination, including color and green monochromatic fundus photography, fluorescein angiography, spectral-domain optical coherence tomography, and adaptive optics imaging.

RESULTS

An asymptomatic 66-year-old Korean woman presented with bilateral white, glistening deposits in a ring pattern around the fovea of both eyes. The dots were highly reflective on green monochromatic images, were not visible on fluorescein angiography, and appeared hyperreflective in the inner retina using spectral-domain optical coherence tomography. Adaptive optics showed polygonal granules ranging from 1 to 10 μ m in size. The patient denied any systemic disorder or the use of any medications related to crystalline retinopathy. The patient had lived in Japan for 35 years before just moving to the United States.

CONCLUSION

The location, small size, and polygonal shape of the dots in white dot fovea are suggestive of intraretinal deposition of crystals, and not cells on the surface of the fovea as has been previously proposed. Carotenoid deposition related to dietary habits is a plausible cause because of the similarity to other retinopathies associated to these compounds.

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.

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.

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.

Müller cells and astrocytes in tractional macular disorders

Tractional deformations of the fovea mainly arise from an anomalous posterior vitreous detachment and contraction of epiretinal membranes, and also occur in eyes with cystoid macular edema or high myopia. Traction to the fovea may cause partial- and full-thickness macular defects. Partial-thickness defects are foveal pseudocysts, macular pseudoholes, and tractional, degenerative, and outer lamellar holes. The morphology of the foveal defects can be partly explained by the shape of Müller cells and the location of tissue layer interfaces of low mechanical stability. Because Müller cells and astrocytes provide the structural scaffold of the fovea, they are active players in mediating tractional alterations of the fovea, in protecting the fovea from such alterations, and in the regeneration of the foveal structure. Tractional and degenerative lamellar holes are characterized by a disruption of the Müller cell cone in the foveola. After detachment or disruption of the cone, Müller cells of the foveal walls support the structural stability of the foveal center. After tractional elevation of the inner layers of the foveal walls, possibly resulting in foveoschisis, Müller cells transmit tractional forces from the inner to the outer retina leading to central photoreceptor layer defects and a detachment of the neuroretina from the retinal pigment epithelium. This mechanism plays a role in the widening of outer lameller and full-thickness macular holes, and contributes to visual impairment in eyes with macular disorders caused by conractile epiretinal membranes. Müller cells of the foveal walls may seal holes in the outer fovea and mediate the regeneration of the fovea after closure of full-thickness holes. The latter is mediated by the formation of temporary glial scars whereas persistent glial scars impede regular foveal regeneration. Further research is required to improve our understanding of the roles of glial cells in the pathogenesis and healing of tractional macular disorders.

Different modes of full-thickness macular hole formation

Full-thickness macular holes (FTMH) are an important cause of visual deterioration. However, different modes of FTMH formation are less investigated. It is also not clear whether the development of edematous cysts contributes to FTMH formation. In this retrospective case series of 30 eyes of 30 patients, we describe using spectral-domain optical coherence tomography different modes of FTMH formation. Morphological alterations of established FTMH are shown in 5 eyes of 5 patients. We found in 2 of 30 eyes investigated that anterior hyaloidal traction induced a hyperreflectivity of the inner Müller cell layer of the foveola prior to FTMH formation. In 3 eyes, FTMH were caused by anterior hyaloidal traction which produced foveal pseudocysts that developed to an outer lamellar hole (OLH) characterized by a disruption of the central outer retina. The OLH developed to a FTMH by the disruption of the inner layer of the foveola. FTMH formation from an OLH by hyaloidal traction was observed also in further 7 eyes. In 2 eyes, the OLH, which preceded FTMH formation, was generated by a serous retinal detachment. In 3 eyes, anterior hyaloidal traction caused a detachment of the fovea from the retinal pigment epithelium (RPE); the subsequent disruption of the foveola resulted in a FTMH. Six eyes showed the development of a FTMH from a degenerative lamellar hole (DLH). In 5 eyes with macular pucker, FTMH were formed by traction of epiretinal membranes (ERM) or hyaloidal traction. Two eyes showed the development of a FTMH by anterior or tangential hyaloidal traction likely without a formation of an OLH. FTMH formation from an OLH proceeded with or without an enlargement of cystic cavities in the foveal walls. The formation of FTMH from a DLH, after a detachment of the fovea, and in macular pucker eyes was associated with a formation of cystic cavities in the foveal walls. The best-corrected visual acuity (BCVA) of eyes with an OLH or FTMH was inversely correlated to the base and minimum diameters of the holes, and with the height of the foveal walls; the highest correlation coefficients were found between the BCVA and the base diameter. The data show that FTMH may be formed via different modes by hyaloidal traction and/or traction of ERM, or after a serous retinal detachment. It is suggested that, after FTMH formation, the impaired fluid clearance through the RPE after detachment of the central outer retina causes the development of edematous cysts in the foveal walls which enlarges the FTMH. The BCVA of eyes with an OLH or FTMH mainly depends on the size of the central photoreceptor-free area.

Glia of the human retina

The human retina contains three types of glial cells: microglia and two types of macroglia, astrocytes and Müller cells. Macroglia provide homeostatic and metabolic support to photoreceptors and neurons required for neuronal activity. The fovea, the site of the sharpest vision which is astrocyte- and microglia-free, contains two populations of Müller glia: cells which form the Müller cell cone in the foveola and z-shaped Müller cells of the foveal walls. Both populations are characterized by morphological and functional differences. Müller cells of the foveola do not support the activity of photoreceptors and neurons, but provide the structural stability of the foveal tissue and improve the light transmission through the tissue to the photoreceptors. This article gives overviews of the glia of the human retina and the structure and function of both Müller cell types in the fovea, and describes the contributions of astrocytes and Müller cells to the ontogenetic development of the fovea.

Multimodal imaging of benign yellow dot maculopathy

PURPOSE

To describe the clinical features of 2 unrelated families affected with Benign Yellow Dot Maculopathy and to analyze anatomical and functional findings of this peculiar phenotype Methods: Case series Results: We retrospectively described 5 patients (3 males, 2 females) affected with Benign Yellow Dot Maculopathy. The mean age at referral was 50,8 years (range 34-69 yrs.). All patients were characterized by a good visual acuity (20/20 in both eyes) and by symmetric multiple yellow dots at the posterior pole in both eyes. In 3 patients (P1, P3, P4) the yellow dots were mainly located at the nasal side of the macula. The yellow dots appeared hyper-autofluorescent at the fundus autofluorescence (FAF) imaging. OCT examination revealed in 3 patients (P1, P3, P4) mild irregularities at the level of the retinal pigment epithelium (RPE) and at the interdigitation (IZ) and ellipsoid zone (EZ). OCT angiography (OCT-A), performed in 3 patients (P1, P4,P5), was normal. Adaptive Optics imaging (AO) showed a peculiar pattern of the cone mosaic: the yellow dots were detectable as hyper-reflective lesions at the macular region. In 2 patients (P1, P4) we reported a follow-up of 2 and 18 years respectively. Genetic examination performed on patient P1 did not reveal pathogenic variants for retinal dystrophies.

CONCLUSIONS

Our work confirmed the benign nature of this peculiar macular phenotype showing a normal macular function and a stable clinical picture during a long-term follow-up. Multimodal imaging allows a detailed detection and monitoring of Benign Yellow Dot Maculopathy.

The primate fovea: Structure, function and development

A fovea is a pitted invagination in the inner retinal tissue (fovea interna) that overlies an area of photoreceptors specialized for high acuity vision (fovea externa). Although the shape of the vertebrate fovea varies considerably among the species, there are two basic types. The retina of many predatory fish, reptilians, and birds possess one (or two) convexiclivate fovea(s), while the retina of higher primates contains a concaviclivate fovea. By refraction of the incoming light, the convexiclivate fovea may function as image enlarger, focus indicator, and movement detector. By centrifugal displacement of the inner retinal layers, which increases the transparency of the central foveal tissue (the foveola), the primate fovea interna improves the quality of the image received by the central photoreceptors. In this review, we summarize ‒ with the focus on Müller cells of the human and macaque fovea ‒ data regarding the structure of the primate fovea, discuss various aspects of the optical function of the fovea, and propose a model of foveal development. The "Müller cell cone" of the foveola comprises specialized Müller cells which do not support neuronal activity but may serve optical and structural functions. In addition to the "Müller cell cone", structural stabilization of the foveal morphology may be provided by the 'z-shaped' Müller cells of the fovea walls, via exerting tractional forces onto Henle fibers. The spatial distribution of glial fibrillary acidic protein may suggest that the foveola and the Henle fiber layer are subjects to mechanical stress. During development, the foveal pit is proposed to be formed by a vertical contraction of the centralmost Müller cells. After widening of the foveal pit likely mediated by retracting astrocytes, Henle fibers are formed by horizontal contraction of Müller cell processes in the outer plexiform layer and the centripetal displacement of photoreceptors. A better understanding of the molecular, cellular, and mechanical factors involved in the developmental morphogenesis and the structural stabilization of the fovea may help to explain the (patho-) genesis of foveal hypoplasia and macular holes.

Incipient white dot fovea syndrome in a child

An 8-year-old girl with normal visual acuity was found to have bilateral macular lesions on retinal examination. Ocular coherence tomography showed discrete perifoveal inner retinal deposits that characterize the "white dot fovea." This report documents the clinical presentation of white dot fovea in early childhood, suggesting that this condition may represent an isolated foveal dystrophy.