POSTERIOR VITREOUS DETACHMENT

Posterior vitreous detachment (PVD) is a common condition in which the vitreous separates from the inner surface of the retina. A PVD is a frequent cause of urgent consultations. It affects men and women equally and occurs in the sixth and seventh decades of life, or earlier in patients with myopia.

Symptoms

The symptoms of PVD include a sudden onset of one or more floaters (often described by the patient as veils or cobwebs). Patients often report small, crescent-shaped flashing lights in the temporal periphery that are stimulated by eye movement and are more easily seen under dark-adapted conditions.

Clinical Features

The presence of a Weiss ring, the circular piece of condensed vitreous that has separated from the optic nerve, confirms the clinical diagnosis of PVD. An optically empty space behind the posterior hyaloid is also suggestive of PVD. There may be associated nerve fiber layer hemorrhage on the optic disc or retina. On clinical examination alone, it is difficult to be certain if the posterior vitreous separation is truly complete. It is possible for the vitreous to be detached over the optic nerve but remain attached in the macula. In patients with PVD, the presence of a vitreous hemorrhage or pigment in the anterior vitreous (tobacco dust or Shaffer’s sign) is highly correlated with the presence of a retinal tear.

Ancillary Testing

Fundus examination should be supplemented by 360° indirect ophthalmoscopy with scleral depression, or three-mirror contact lens examination of the periphery, or both, in order to exclude a retinal tear. Incomplete vitreous separation (with the posterior vitreous still attached in the macula) may be seen on optical coherence tomography or B-scan ultrasonography. Ultrasound examination is very helpful in confirming the diagnosis of PVD when vitreous hemorrhage is present.

Pathology/Pathogenesis

Degradation of the vitreous collagen matrix (syneresis) accompanied by thinning of the posterior hyaloid results in a sudden disruption of the posterior hyaloid membrane. This breakdown allows fluid from the vitreous body to enter the preretinal space, and dissect the relatively weak adhesion between the vitreous and

the inner retina.

Treatment/Prognosis

No treatment is required for PVD. Patients who present with an acute PVD and have no associated findings are at a relatively low risk for developing a retinal tear. The risk of developing a retinal tear is greatest in patients who present with PVD and vitreous hemorrhage and/or peripheral vitreoretinal traction. In these latter patients, a follow-up visit should be scheduled for 3 to 6 weeks after the onset of symptoms. All patients with PVD should be warned of the signs and symptoms of retinal tear and detachment.

Systemic Evaluation

There are no known systemic associations of PVD.

A Weiss ring (arrow) is seen suspended in front of the optic disc. Note that the retinal details are blurred because the focal plane of the Weiss ring is anterior to the optic disc/retina.

Patients with acute posterior vitreous detachment are at risk for developing retinal tears. Acute, symptomatic horseshoe tears should be treated to reduce the risk of retinal detachment.

Retroillumination reveals a prominent Weiss ring in a patient with a posterior vitreous detachment.

This photograph was taken during pars plana vitrectomy. It demonstrates the advancing line of vitreous separation as the posterior hyaloid is peeled off the retina.

Proliferative vitreoretinopathy (PVR) is a modified wound-healing response that occurs in eyes with rhegmatogenous retinal detachment. It can occur following primary retinal detachments (especially in patients in whom there is a delay in repairing the detachment), or following surgical repair of retinal detachment.

Symptoms

Contracting PVR membranes can reopen treated retinal breaks, or cause new breaks, thus leading to retinal redetachment and associated sudden visual loss. In the absence of retinal breaks, PVR is asymptomatic, unless there are membranes on the macula, causing symptoms of metamorphopsia and central blurring.

Clinical Features

The clinical features of PVR have been classified according to severity and location. Grade A consists of vitreous haze and pigment in the vitreous. In grade B there is wrinkling of the retina with vascular tortuosity. In grade C, full-thickness retinal folds (star folds) have developed. The extent of the folds in clock hours and the location (anterior or posterior) are dictated by numbers and the letters A and P. The notation CP2, for example, means two clock hours of posterior full-thickness retinal folds.

Ancillary Testing

In the presence of dense media opacity, ultrasound examination can be helpful in determining the configuration of the retinal detachment.

Pathology/Pathogenesis

Proliferative vitreoretinopathy results in the formation of fibrocellular contractile membranes on both surfaces of the detached neurosensory retina, on the posterior vitreous face, and in the vitreous base. Inflammation and breakdown of the blood-ocular barrier are followed by migration and proliferation of retinal pigment epithelial cells. Membranes are formed by cells laying down collagen under the influence of growth factors and adhesion molecules. Finally, contraction of the membranes occurs, leading to retinal shortening.

Treatment/Prognosis

Proliferative vitreoretinopathy is a serious complication of retinal detachment surgery, and may lead to severe loss of vision. Anterior PVR compromises the function of the ciliary body, leading to hypotony. Treatment requires vitrectomy surgery to relieve traction, treatment of retinal breaks, and the insertion of a tamponade agent (either long-acting gas or silicone oil). Success rates of treatment vary according to the severity of the disease, but functional results are often poor.

Systemic Evaluation

There are no known systemic associations of PVR.

Proliferative vitreoretinopathy is characterized by fullthickness retinal folds radiating from an area of fibrocellular proliferation.

This fundus photograph demonstrates an early funnelshaped retinal detachment in a patient with proliferative vitreoretinopathy.

The classic finding in patients with proliferative vitreoretinopathy is a star fold, as seen in this patient following a retinal detachment.

B-scan ultrasound of the same patient reveals a characteristic pattern of a funnel-shaped retinal detachment.