Characteristics of Posterior Precortical Vitreous Pockets and Cloquet’s Canal in Patients with Myopia by Optical Coherence Tomography

The Topographic Relationships and Geographic Distribution of Prevascular Vitreous Fissures and Cisterns Assessed by Ultrawidefield En Face Vitreous Images

Purpose

To determine the topographic relationships and geographic distribution of prevascular vitreous fissures (PVFs) and cisterns across the entire posterior vitreous membrane in healthy subjects, using ultrawidefield en face and cross-sectional swept-source OCT (SS-OCT) images.

Design

Observational cross-sectional study.

Participants

Ninety-six eyes of 96 healthy participants (age range, 20-49 years) without posterior vitreous detachment.

Methods

For each eye, a 29 × 24-mm SS-OCT volume scan was obtained, along with standardized horizontal and vertical scans through the fovea.

Main Outcome Measures

Ultrawidefield en face and cross-sectional images were analyzed to assess the topographic relationships and geographic distribution of PVFs and cisterns in the posterior vitreous.

Results

En face imaging readily distinguished various preretinal liquefaction spaces throughout the posterior vitreous, extending to near the equator. Aside from the posterior precortical vitreous pocket (PPVP) and the area of Martegiani, all preretinal liquefied fissures and cisterns were distributed along superficial retinal vessels, suggesting they originated from prevascular vitreous liquefaction. In 96 eyes of healthy young and middle-aged adults, PVFs were identified in all participants, presenting a continuous course. Cisterns were detected in 79 eyes (82.3%) and were distributed as follows: superotemporal (91.1%), infratemporal (63.3%), supranasal (41.8%), and inferonasal (22.8%), respectively. The superotemporal cistern was most frequently observed (P < 0.001), and cisterns were more likely to involve multiple quadrants with age (P = 0.005). Additionally, all preretinal liquefaction spaces, including the PPVP, PVFs, and cisterns, were consistently located overlying the vitreoretinal tightly adhered regions.

Conclusions

Ultrawidefield en face vitreous imaging in healthy young and middle-aged adults revealed that (1) PVFs distributed along superficial retinal vessels with continuous course; (2) cisterns may develop from PVFs and are more common in the superotemporal quadrant; (3) cisterns appear early in life and become more widespread with age; (4) preretinal vitreous liquefaction follows a stereotypic pattern, aligning along regions of firm vitreoretinal adhesion.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Characteristics of posterior precortical vitreous pockets visualized by swept-source OCT and en face OCT

To determine the characteristics of posterior precortical vitreous pockets (PPVPs) and to observe vitreous changes in myopic eyes by swept-source optical coherence tomography (SS-OCT) and en face imaging in a cohort of the Chinese Han population. This was a cross-sectional study. Volunteers (235 participants, 374 eyes) received an SS-OCT examination. The heights and widths of the PPVPs were measured by SS-OCT. The area of the PPVPs was measured on en face images. The relationships between PPVP size and sex, age, axial length (AL) and spherical equivalent (SE) were evaluated. The mean width and height were 6711.64 ± 1241.87 μm and 662.47 ± 326.39 μm, respectively. The area of the PPVPs was 30.296 ± 9.114 mm2. Boat-shaped, oval, and hook-shaped PPVPs were observed in 73.26%, 21.12%, and 5.62% of all eyes, respectively; 73.53% of all PPVPs had channels communicating with Cloquet's tubes. There was a significant difference in the PPVP width among the participates over and under 50 years old (t = -2.508, P = 0.031). Age had a positive correlation with the PPVP width (r = 0.53, P = 0.001). The PPVP height showed significant differences among the different myopia groups (F = 3.618, P = 0.013). SE had a negative correlation with the PPVP height (r = -0.176, P = 0.001). However, there were no correlations between the AL and the width, height or area of the PPVPs (P = 0.117; P = 0.334; P = 0.057, respectively). Age and myopia affect the size of PPVPs. SS-OCT greatly facilitates visualization of the complex structure of the vitreous.

IMI-Nonpathological Human Ocular Tissue Changes With Axial Myopia

Purpose

To describe nonpathological myopia-related characteristics of the human eye.

Methods

Based on histomorphometric and clinical studies, qualitative and quantitative findings associated with myopic axial elongation are presented.

Results

In axial myopia, the eye changes from a spherical shape to a prolate ellipsoid, photoreceptor, and retinal pigment epithelium cell density and total retinal thickness decrease, most marked in the retroequatorial region, followed by the equator. The choroid and sclera are thin, most markedly at the posterior pole and least markedly at the ora serrata. The sclera undergoes alterations in fibroblast activity, changes in extracellular matrix content, and remodeling. Bruch's membrane (BM) thickness is unrelated to axial length, although the BM volume increases. In moderate myopia, the BM opening shifts, usually toward the fovea, leading to the BM overhanging into the nasal intrapapillary compartment. Subsequently, the BM is absent in the temporal region (such as parapapillary gamma zone), the optic disc takes on a vertically oval shape, the fovea-optic disc distance elongates without macular BM elongation, the angle kappa reduces, and the papillomacular retinal vessels and nerve fibers straighten and stretch. In high myopia, the BM opening and the optic disc enlarge, the lamina cribrosa, the peripapillary scleral flange (such as parapapillary delta zone) and the peripapillary choroidal border tissue lengthen and thin, and a circular gamma and delta zone develop.

Conclusions

A thorough characterization of ocular changes in nonpathological myopia are of importance to better understand the mechanisms of myopic axial elongation, pathological structural changes, and psychophysical sequelae of myopia on visual function.

Machine learning-based 3D modeling and volumetry of human posterior vitreous cavity of optical coherence tomographic images

The structure of the human vitreous varies considerably because of age-related liquefactions of the vitreous gel. These changes are poorly studied in vivo mainly because their high transparency and mobility make it difficult to obtain reliable and repeatable images of the vitreous. Optical coherence tomography can detect the boundaries between the vitreous gel and vitreous fluid, but it is difficult to obtain high resolution images that can be used to convert the images to three-dimensional (3D) images. Thus, the purpose of this study was to determine the shape and characteristics of the vitreous fluid using machine learning-based 3D modeling in which manually labelled fluid areas were used to train deep convolutional neural network (DCNN). The trained DCNN labelled vitreous fluid automatically and allowed us to obtain 3D vitreous model and to quantify the vitreous fluidic cavities. The mean volume and surface area of posterior vitreous fluidic cavities are 19.6 ± 7.8 mm³ and 104.0 ± 18.9 mm² in eyes of 17 school children. The results suggested that vitreous fluidic cavities expanded as the cavities connects with each other, and this modeling system provided novel imaging markers for aging and eye diseases.

An en face swept source optical coherence tomography study of the vitreous in eyes with anterior uveitis

PURPOSE

To analyse vitreous anatomy patients with anterior uveitis (AU) using swept source optical coherence tomography (SS-OCT).

METHODS

Patients with newly diagnosed AU and healthy participants were scanned using 16-mm SS-OCT B-scans and 12 × 12 mm cube centred at the fovea. Linear SS-OCT scans were evaluated to identify the premacular bursa (PB) above the macula and the Cloquet's canal above the optic disc. A dynamic evaluation of the 12 × 12 mm cube enabled en face measurement of the vertical and horizontal diameters of the PB and the presence/absence of communication between the PB and Cloquet's canal.

RESULTS

One hundred and thirty-five subjects were included in the study. Forty-five patients were healthy (mean age 33.47 years). En face measurements of the horizontal and vertical PB mean diameters were 5.2 mm and 4.7 mm. In 90 subjects with AU (mean age 30.10 years), the mean horizontal and vertical diameter of the PB were significantly larger (p < 0.01). Thirty-seven eyes with AU presented with cystoid macular oedema (CME). The mean diameters of the PB in this subgroup were significantly larger (p < 0.01). In 75% of the entire cohort (51% of eyes in the control group, 87% of eyes with AU and 100% of eyes with AU and CME), a channel connecting the PB and Cloquet's canal could be identified.

CONCLUSIONS

SS-OCT identification of a connecting channel between the PB and the Cloquet's canal suggests that inflammatory cytokines may drain from the anterior chamber through this system of channels, thus increasing the risk of CME.

Wide-field swept source optical coherence tomography evaluation of posterior segment changes in highly myopic eyes

BACKGROUND

To investigate the features in the posterior pole of highly myopic (HM) eyes using a wide-field high-resolution swept source optical coherence tomography (SS OCT).

METHODS

This observational cross-sectional study involved 262 eyes of 139 patients, who were diagnosed as HM and had consecutively been examined by SS OCT in the Ophthalmology Department of the Peking Union Medical College Hospital between March 2019 and December 2019. The characteristics of OCT images were documented and analyzed.

RESULTS

In our study, SS OCT could demonstrate the entire layer of the choroid and detect the sclera in all eyes. The mean subfoveal retinal/choroidal/scleral thickness were 204.84 ± 119.86 μm, 92.80 ± 75.78 μm and 394.734 ± 123.09 μm, respectively. 138 eyes (52.67%) had posterior precortical vitreous pocket. Myopic foveoschisis was detected in 110 eyes (41.98%), and significantly associated with the presence of posterior staphyloma. 36 eyes (13.74%) had DSM in our study, of which 8 eyes (22.22%) showed a round dome, 16 (44.44%) were horizontal oval-shaped, 9 (25%) were vertical oval-shaped and 3 (8.34%) were oblique oval-shaped. Both SFCT and SFST were inversely and significantly associated with age and refractive errors. Macular neovascularization was significantly correlated with intrascleral vessels. Different deformation of the sclera and posterior staphyloma were vividly identified on SS OCT images.

CONCLUSIONS

This study provided a relatively comprehensive picture of posterior pole in HM eyes. Such good visualization of ocular fundus provided by wide-field SS OCT could be useful for the therapy option, disease condition monitoring and pathogenesis investigation.

Choroidal remodeling distribution pattern in the macular region in Chinese young patients with myopia

Background

The pathogenesis of myopia has been found to be associated with the blood supply of the choroid. This study aimed to determine the relationship between the distribution pattern of choroidal remodeling and the degree of myopia in young patients.

Methods

Young patients (age < 18 years) with the spherical equivalent of less than − 12 diopters (D) were included. Spectral-domain optical coherence tomography (SD-OCT) with enhanced depth imaging (EDI) modality was used to measure the choroidal thickness (CT) and choroidal vascularity index (CVI) in the macular regions. CVI was calculated as the proportion of luminal area to choroidal area and was measured within 1 mm and 3 mm nasal (N1 and N3), temporal (T1 and T3), superior (S1 and S3), and inferior (I1 and I3) to the foveal center. CVI was compared across different ages (i.e., 5 ~ 9 years, 10 ~ 13 years, and 14 ~ 18 years), axial lengths (ALs) (i.e., 21.00 ~ 25.00 mm and 25.01 ~ 29.00 mm), and spherical equivalents (SEs) (i.e., SE > -0.5D, − 0.5 ~ − 3.0D, − 3.01 ~ − 6.0D, and < − 6.0D). Linear regression analysis was applied to assess the association between independent (i.e., age, AL, SE, and intraocular pressure) and dependent variables (i.e., CVI of different regions).

Results

One hundred sixty-four eyes from 85 volunteers were included. The mean CT in the central foveal was 269.87 ± 63.32 μm (93.00 μm to 443.00 μm). The mean subfoveal-CVI was 67.66 ± 2.40% (57.84 to 79.60%). Multiple linear regression results revealed significant correlations between SE and T1-CVI (p < 0.05, r² = 0.082, β = 0.194), N1-CVI (p < 0.05, r² = 0.039, β = 0.212). Simple linear regression results revealed that T1-CVI (p < 0.05, r² = 0.09) and T3-CVI (p < 0.05, r² = 0.05) were negatively correlated with SE; N1-CVI (p < 0.05, r² = 0.05) and N3-CVI (p < 0.05, r² = 0.04) were negatively correlated with SE.

Conclusions

CVI in the horizontal meridian underwent the largest change as myopia worsened. Temporal and nasal CVIs within the r = 1 mm, and r = 3 mm subfoveal range were positively associated with the degree of myopia in young patients. The CVI value may be used to assess the vascular status of the choroid and be a potential marker of myopic progression.

Expression of Lymphatic Markers in the Berger's Space and Bursa Premacularis

We previously reported that the bursa premacularis (BPM), a peculiar vitreous structure located above the macula, contains numerous cells expressing markers of lymphatic endothelial cells, such as podoplanin and LYVE-1. Herein, we examined the expression of lymphatic markers in the Berger’s space (BS), BPM, and vitreous core (VC). BS, BPM, and VC specimens were selectively collected in macular hole and epiretinal membrane patients during vitrectomy and were then immunostained with antibodies for podoplanin, LYVE-1, and fibrillin-1 and -2. By visualization using triamcinolone acetonide, the BS was recognized as a sac-like structure with a septum located behind the lens as well as BPM. Those tissues adhered to the lens or retina in a circular manner by means of a ligament-like structure. Immunostaining showed intense expression of podoplanin and LYVE-1 in the BS. Both BS and BPM stained strongly positive for fibrillin-1 and -2. The VC was faintly stained with antibodies for those lymph-node markers. Our findings indicate that both BS and BPM possibly belong to the lymphatic system, such as lymph nodes, draining excess fluid and waste products into lymphatic vessels in the dura mater of the optic nerve and the ciliary body, respectively, via intravitreal canals.

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.