Imaging the Vitreous With a Novel Boosted Optical Coherence Tomography Technique

Abstract

Purpose: To evaluate the anatomic changes in the vitreous associated with evolving posterior vitreous detachment over the macula.Methods: A novel scanning method by which four A-scans at each position were averaged before the Fourier transform that boosted the image quality sufficiently such that frame averaging could occur. B-scans and volume rendered images of eyes with evidence of any partial separation of the vitreous in the macular regions were evaluated.Results: There were 43 eyes of 23 subjects with particular attention paid to the findings of seven eyes with various stages of posterior vitreous detachment occurring over the macula. In eyes from young subjects with no vitreous degeneration, the outer vitreous showed a diffuse, poorly defined increase in reflectivity in the region where the vitreous cortex was expected to be. In eyes with vitreous degeneration, there was a hyperreflective zone, called the cortical vitreous condensation, that coursed parallel to the curvature of the retina. The posterior vitreous face elevated from the retina with either a well-defined, smooth outer surface, consistent with the posterior vitreous membrane, or a poorly defined flocculent outer border. The cortical vitreous near the fovea was thin and in eyes in the process of posterior vitreous detachment had visible tears. In more advanced eyes, a circular dehiscence of the cortical vitreous in the central macula occurred with herniation of the vitreous gel through the hole. Conclusion:The methodology produced images of unprecedented clarity that highlighted several newly described details concerning the vitreous changes associated with posterior vitreous detachment over the macula.

The Way Patients See Floaters

“…14,15 Type II collagen spontaneously aggregates with other collagen fibrils because of mutual attraction to form collagen fibers. 14,15 Excessive aggregation of Type II collagen is prevented by Type IX collagen, which sequesters Type II collagen into inner fibers when hybrid fibrils between Types II and IX collagen are made. 14,15 As one ages, there is exponential loss of Type IX collagen, which leads to exposure of sequestered Type II collagen and spontaneous aggregation of Type II collagen fibrils.…”

“…14,15 Excessive aggregation of Type II collagen is prevented by Type IX collagen, which sequesters Type II collagen into inner fibers when hybrid fibrils between Types II and IX collagen are made. 14,15 As one ages, there is exponential loss of Type IX collagen, which leads to exposure of sequestered Type II collagen and spontaneous aggregation of Type II collagen fibrils. 14,15 Vitreous cisterns also form when pockets of liquid vitreous result from the collection of solubilized hyaluronan and its associated water molecules 14,15 (Figure 4).…”

“…14,15 As one ages, there is exponential loss of Type IX collagen, which leads to exposure of sequestered Type II collagen and spontaneous aggregation of Type II collagen fibrils. 14,15 Vitreous cisterns also form when pockets of liquid vitreous result from the collection of solubilized hyaluronan and its associated water molecules 14,15 (Figure 4).…”

Role of Optical Coherence Tomography in Management of Acute Posterior Vitreous Detachment and Its Complications

“…Enhanced vitreous imaging OCT uses six radial scans with a scan width of 30°c entered at the fovea and uses built-in functions, including focusing on the vitreous, positioning the retinal layers inferiorly to allow maximum imaging depth into the vitreous, and adjusting the image brightness to allow optimal imaging resolution and depth into the vitreous. 29,30 Such built-in functions to enhance imaging of the vitreous complex can be adopted for use in other OCT modalities to enhance visualization of the vitreous.…”

Posterior vitreous detachment in absentia

“…Historically, much has been theorised on the combined biological changes of syneresis and synchisis leading in some ill-defined manner to weakening adhesion at the vitreoretinal interface, inducing the outer vitreous cortex to separate from the inner limiting membrane of the retina. In contrast, more recent research [ 11 – 14 ] has demonstrated that PVD is not simply an inevitable consequence of age related syneresis but more a distinct immunohistochemically confirmed separation of the posterior hyaloid membrane (PHM) from the retinal surface and that separation of this type IV collagen basement membrane can still occur in individuals in whom all cortical gel (syneretic or otherwise) has been previously removed during by vitrectomy surgery.…”