In vivo imaging of the fibrillar architecture of the posterior vitreous and its relationship to the premacular bursa, Cloquet’s canal, prevascular vitreous fissures, and cisterns

Proliferative vitreoretinopathy: a revised concept of retinal injury and response

Previous concepts for the pathogenesis of proliferative vitreoretinopathy (PVR) have focused on the central role of retinal pigment epithelium cells only, potentially contributing to the lack of clinical advances. More recent studies have demonstrated the essential role of retinal glial cells in the PVR healing response but failed to identify a consistent triggering mechanism.We propose a revised concept for the pathogenesis of PVR based on retinal injury and response. A posterior vitreous detachment (PVD) is invariably present in patients with rhegmatogenous retinal detachment and PVR. There is evidence to suggest that the shearing forces of acute PVD can cause mechanical injury to the inner retina and trigger a subsequent intraretinal glial healing response. That response is characterised by subclinical glial cell activation and proliferation that may then be amplified into full-blown PVR by coexisting pathology such as retinal breaks and detachment.Whether a PVD causes interface pathology depends on the plane of separation of the posterior vitreous and areas of increased vitreoretinal adhesions. If the vitreous separates in a plane or location that damages the inner retina then glial cell activation and proliferation are likely to develop. The severity of the subclinical inner retinal damage may then represent one of the missing links in our understanding of the pathogenesis of PVR and would explain many of the findings we encounter in clinical practice. Controlling the process of acute PVD and subsequent intraretinal response may be essential in the prevention and management of PVR.

[Age-related changes in human vitreous]

There are two main age-related changes that can occur in the vitreous body of healthy individuals throughout life: liquefaction (synchesis) and aggregation of collagen fibrils into dense bundles (syneresis). Progressive age-related degradation leads to posterior vitreous detachment (PVD). At present many classifications of PVD exist, in which authors relied either on the morphological features, or on the differences in pathogenesis before and after widespread use of OCT. The course of PVD can be either normal or anomalous. Physiological PVD induced by age-related vitreous changes progresses in specific stages. The review emphasizes that PVD can occur initially not only in the central zone of the retina, but also on the periphery with further spread to the posterior pole. Anomalous PVD can lead to various negative effects on the retina, as well as on the vitreous as a result of traction in the area of vitreoretinal interface.

Hypodense regions in the peripapillary region increased the risk of macular retinoschisis detected by optical coherence tomography

Purpose

The purpose of the present study was to investigate the clinical features of peripapillary regions in patients with myopic macular retinoschisis (MRS) and its association with the development of retinoschisis (RS).

Methods

In this cross-sectional study, high-myopic patients with or without MRS were recruited, and the hypodense regions were analyzed in the peripapillary regions. The vitreoretinal adhesions around both macular and paravascular arcades were compared between groups. The risk factors for the development of MRS were analyzed by logistic regression.

Results

Of 88 myopic eyes, MRS was detected in 45 eyes (51%). The eyes with MRS showed a higher rate of peripapillary and paravascular retinoschisis (P < 0.001 and P = 0.006). Hypodense regions were detected in 25 eyes (20.35%). Higher rates of horizontal and vertical macular MRS were detected in the hypodense group (P = 0.012 and P = 0.002). Lower refractive error, longer axial length, and higher rates of outer retinoschisis both in horizontal and vertical macular regions were observed in the hypodense group (P = 0.012, P = 0.006, P = 0.038, and P = 0.034). Higher rates of inner and outer retinoschisis, vitreoschisis, and microfolds along superior vascular arcade were detected in the hypodense group (P = 0.005, P = 0.001, P = 0.014, and P = 0.014). Higher rates of internal limiting membrane (ILM) detachment, inner and outer RS were detected along the inferior vascular arcade in the hypodense group (P = 0.008, P = 0.001, and P = 0.028). Hypodense regions, the axial length and PICC (peripapillary intrachoroidal cavitation) were significantly correlated with the severity of MRS (Odds ratio = 0.207, P = 0.010; Odds ratio = 1.399, P = 0.016; Odds ratio = 0.142, P = 0.010).

Conclusions

The hypodense regions were likely to affect outer retinoschisis both in macular and paravascular regions. It was a risk factor for the development of MRS.

Imaging the Vitreous with a Novel Boosted Optical Coherence Tomography Technique: Vitreous Degeneration and Cisterns

PURPOSE

To evaluate the degenerative findings including cistern formation in the premacular vitreous using optical coherence tomography (OCT).

METHODS

A novel enhanced vitreous imaging method by which 4 A-scans at each position were averaged prior to the Fourier transform increased the image quality per frame so that subsequent image registration for averaging could occur. Analysis of B-scans and volume rendered images of eyes in subjects of various ages was performed.

RESULTS

There were 43 eyes of 23 subjects ranging in age from 23 - 68 years. The texture in the vitreous images suggests specific orientations of the vitreous fibers in the macular region; there were fibers circumferential to the retina immediately anterior to the premacular bursa. The pattern of the vitreous fibers seemed less well defined internal to the zone of circumferential fibers. In younger eyes, there were striations oriented in a roughly inferior to superior direction in this zone. In older eyes there were striations in the same orientation but actually were alternating zones of vitreous synchysis and syneresis. In these same eyes numerous cisterns appeared at various levels in the vitreous gel. With extensive vitreous condensation and synchysis, definition of the premacular bursa was lost.

CONCLUSIONS

With this novel method of enhanced vitreous imaging, the vitreous appeared to have stereotypic patterns of degeneration. The formation of vitreous syneresis and synchysis may be related to organization architecture of the vitreous, including the pattern of vitreous collagen deposition, and the effects of eye motion through decades of time.

STARDUST SIGN AND RETINAL TEAR DETECTION ON SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

The causes of floaters include posterior vitreous detachment and fundus hemorrhage, both of which are risk factors for retinal tears. We observed the vitreous of patients with floaters using swept source optical coherence tomography.

METHODS

Fundus examination was performed, and the vitreous was observed using swept source optical coherence tomography in 202 eyes of 202 patients with floaters. Patients with uveitis, diabetic retinopathy, and other fundus diseases were excluded.

RESULTS

Swept source optical coherence tomography revealed posterior vitreous detachment in 145 of 202 eyes (71.8%) and dot reflex like stardust in the vitreous in 42 of 202 eyes (20.8%). Posterior vitreous detachment occurred in 35 of 42 eyes (83.3%) and 110 of 160 eyes (68.8%) in the stardust (+) and stardust (-) groups, respectively; a significant difference was observed (P <0.001). In the stardust (+) group, 11 of 42 eyes (26.2%) had retinal tears with posterior vitreous detachment and 21 of 42 eyes (50.0%) had fundus hemorrhage. Three of 160 eyes (1.9%) and 4 of 160 eyes (2.5%) in the stardust (-) group had retinal tears with posterior vitreous detachment and fundus hemorrhage, respectively. Both tears and fundus hemorrhage were more frequent in the stardust (+) group than in the stardust (-) group (P <0.001).

CONCLUSION

The stardust sign on swept source optical coherence tomography indicates the risk of retinal tear.

Determining posterior vitreous structure by analysis of images obtained by AI-based 3D segmentation and ultrawidefield optical coherence tomography

AIMS

To determine the three-dimensional (3D) structure of the vitreous fluid including the posterior precortical vitreous pockets (PPVP), Cloquet's canal and cisterns in healthy subjects by AI-based segmentation of the vitreous of swept-source optical coherence tomography (OCT) images. In addition, to analyse the vitreous structures over a wide and deep area using ultrawidefield swept-source OCT (UWF-OCT).

METHODS

Ten eyes of six patients with the mean age was 40.7±8.4 years and the mean refractive error (spherical equivalent) was -3.275±2.2 diopters were examined.

RESULTS

In the UWF OCT images, the structure of the vitreous was observed in detail over 23 mm wide and 5 mm area. AI-guided analyses showed the complex 3D vitreous structures from any angle. Cisterns were observed to overlie the PPVP from the anterior. The morphology and locations of the cisterns varied among the subjects but tended to be similar in the two eyes of one individual. Cisterns joined the PPVPs superior to the macula to form a large trunk. This joined trunk was clearly seen in 3D images even in eyes whose trunk was not detected in the B scan OCT images. In some eyes, the vitreous had a complex appearance resembling an ant nest without large fluid-filled spaces.

CONCLUSIONS

A combination of UWF-OCT and 3D imaging is very helpful in visualising the complex structure of the vitreous. These technologies are powerful tools that can be used to clarify the normal evolution of the vitreous, pathological changes of vitreous and implications of vitreous changes in various vitreoretinal diseases.

PREVALENCE OF VITREOUS CORTEX REMNANTS IN EYES WITH PRIMARY RHEGMATOGENOUS RETINAL DETACHMENT UNDERGOING VITRECTOMY

BACKGROUND/PURPOSE

To evaluate the prevalence and extent of vitreous cortex remnants (VCR) on the surface of the retina in eyes with primary rhegmatogenous retinal detachment (RRD) and posterior vitreous detachment.

METHODS

Triamcinolone acetonide was injected in the vitreous cavity of 100 consecutive cases of acute primary RRD undergoing pars plana vitrectomy. A multivariate regression analysis was performed to determine any association between the presence and pattern of stained VCR on the surface of the retina and the following variables: age, diabetes, axial length, phakic status, extent of RRD, and macular status.

RESULTS

Vitreous cortex remnants were found in 42 eyes. These were focal in eight eyes and diffuse in 34 eyes. Age was the only strong and independent risk factor associated with the presence of VCR (P = 0.0019). Age (P < 0.0001), axial length (P = 0.0037), and phakia (P = 0.01) were independent risk factors associated with the diffuse pattern. Neither diabetes, extent of RRD, nor macular status were significant risk factors for the presence or extent of VCR.

CONCLUSION

Older patients with primary RRD and posterior vitreous detachment seem to be at a higher risk of having diffuse VCR. Further studies are needed to investigate the relevance of VCR in the pathogenesis, progression and treatment of RD.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.