Posterior vitreous detachment (PVD) is a common degenerative, usually bilateral, condition carrying with it the risk of damage to the associated retina. The vitreous is normally attached at the following locations:
- a loose ring shaped attachment at the macula;
- a ring shaped attachment around the margin of the optic nerve, related to the developmental tubular structure known as Cloquet’s canal;
- the vitreous base is an attachment area 2 to 3mm wide at the ora serrata;
- the vitreous may also be loosely adherent at the retinal blood vessels;
- Mittendorf’s dot is the attachment of Cloquet’s canal at the posterior lens surface.
With age the vitreous becomes more liquefied (synchysis senilis) and shrinks (vitreous syneresis). Fine collagen fibrils in the vitreous may congregate, forming small “floating” opacities. The vitreous moves more readily with eye movements or trauma, tugging the hyaloid membrane anteriorly, away from the retinal internal limiting membrane. Retinal tearing or edema may subsequently occur. If there is flow of the liquid vitreous under the Retinal Pigment Epithelium (RPE), it may lead to rhegmatogenous retinal detachment.
PVD is commonly associated with visual symptoms. The patient may observe small dark spots or lines close to the visual axis, known as ‘floaters’. They may also report brief flashes of light in their peripheral vision (photopsia) or, less commonly, central distorted vision (metamorphopsia).
Examination of the vitreous is a dynamic procedure, in order to observe the subtle opacities within the transparent vitreous or the displaced posterior hyaloid face. The most common vitreous opacity associated with PVD has a ring or partial-ring shape anterior to the optic nerve head (Weiss ring). PVD at the macula may cause transient macular edema.
RPE pigment granules that enter the vitreous are known as tobacco dust or Shafer’s sign. These are virtually pathognomonic of a retinal tear or retinal detachment. Small pre-retinal or diffuse vitreous hemorrhages may occur. Careful evaluation of the peripheral retina through dilated pupils with indirect ophthalmoscopy is indicated, to identify any retinal breaks or tears.
Very common (greater than 1/10) particularly in older patients or in younger patients with myopia
A symptomatic PVD represents a risk factor for significant retinal complications such as retinal breaks, detachment or macular hole.
Macular hole, Vitreomacular Traction Syndrome, Epiretinal membrane, Retinal detachment – classification, White without pressure, Vitreous Anomalies
A PVD is only urgent if there are concurrent signs of retinal breaks or retinal detachment.
Ocular coherence tomography (OCT) may show the vitreous face (hyaloid membrane) having detached and separated from the retina; indicating the resolution of vitreo-retinal traction in that zone.
Retinal detachment is most likely to occur within 6 months of a symptomatic PVD; by which time the vitreo-retinal traction is likely to have stabilized. If the PVD has caused an acute retinal tear, then retinal detachment is most likely to occur within one to two months subsequent.
If the only signs and symptoms relate to vitreous floaters, the patient is reassured, and advised to return for annual review and at once if symptoms change. PVD alone is not usually an indication for vitrectomy
Posterior vitreous traction at the macula.
Vitreous fl oater