Proliferative Vitreoretinopathy (PVR) is a serious complication that develops primarily following surgery to repair a retinal detachment. This condition involves an abnormal, excessive wound-healing response leading to the formation of contractile scar tissue inside the eye. PVR is the most common cause of failure in initially successful retinal detachment surgery, accounting for up to 75% of cases where the retina detaches a second time. This scarring can result in severe, often uncorrectable, vision loss or blindness if left untreated.
Understanding Proliferative Vitreoretinopathy
The development of PVR is rooted in a cellular mechanism triggered by a break in the retina, which allows cells to enter the vitreous cavity. The main culprits are retinal pigment epithelial (RPE) cells, which normally form a single layer beneath the light-sensing photoreceptors. When the retina detaches, these RPE cells are released and begin to migrate and proliferate in an uncontrolled manner.
The RPE cells undergo epithelial-mesenchymal transition, changing their form and function to resemble fibroblasts, which are scar-forming cells. These transformed cells lay down an extracellular matrix, creating fibrotic membranes both on the surface of the retina (epiretinal membranes) and beneath it (subretinal membranes). These membranes are highly contractile.
This contraction exerts a powerful, inward pulling force, or traction, on the delicate neural retina. This force physically pulls the retina away from its underlying support structure, causing a tractional redetachment. This biological process typically occurs weeks to months after the initial event, complicating what was thought to be a successful surgical repair.
Recognizing the Signs and Risk Factors
A patient experiencing the onset of PVR often notices a gradual or sudden deterioration of vision following initial retinal detachment repair. Symptoms include an increase in floaters or flashes of light caused by the contracting membranes pulling on the retina. A shadow or fixed veil may appear in the peripheral vision, indicating a new detachment. Central vision loss occurs if the macula is involved in the redetachment.
Several factors increase the risk of developing PVR. The severity of the initial retinal detachment is a major predictor, particularly if there are large or multiple retinal tears or if the detachment was present for a long period before surgery. Ocular trauma, such as a severe blow or open globe injury, carries a very high risk, sometimes up to 50% of cases.
Other conditions that increase risk include significant bleeding inside the eye (vitreous hemorrhage), chronic inflammation (uveitis), or having had multiple previous eye surgeries. The majority of PVR cases develop within the first four to eight weeks following the initial retinal detachment surgery.
Surgical Treatment Approaches
Surgical intervention represents the only effective treatment option for PVR, as no approved pharmacological agent exists to prevent or halt the scarring process. The standard approach involves pars plana vitrectomy, where the vitreous gel is removed from the eye’s interior. This allows the surgeon access to the retinal surface.
Once the vitreous is cleared, the surgeon performs membrane peeling using specialized instruments like micro-forceps or diamond-dusted scrapers. This intricate process involves carefully peeling away the contractile epiretinal and subretinal membranes from the surface of the retina to release the traction. Complete removal of this scar tissue is necessary to allow the retina to flatten back into its correct anatomical position.
After the retina is free of traction, it is reattached using a temporary heavy liquid, which gently pushes the retina back onto the underlying tissue. The reattached retina is then secured using laser energy (endolaser photocoagulation) around the tears or detachment borders to create a permanent seal.
Finally, an intraocular tamponade agent is placed inside the eye to provide internal support while the retina heals. The choice is between a long-acting gas (e.g., perfluoropropane) or silicone oil. Silicone oil is often preferred in severe PVR cases because it provides mechanical support for a longer duration, which is necessary to counteract the high potential for scar tissue reformation. The gas eventually dissipates and is replaced by the eye’s natural fluid, but silicone oil requires a second surgical procedure for its removal once the retina is stable.
Prognosis and Managing Recurrence
PVR has a guarded long-term outlook. Despite advanced surgical techniques, visual recovery is often limited due to permanent damage to the photoreceptors caused by prolonged detachment and the scarring itself. The anatomical success rate is typically between 45% and 85% after a single PVR surgery, but the rate of achieving useful vision is lower.
A significant challenge in managing PVR is the high rate of recurrence, where the scar tissue begins to form again after surgery. This is because the underlying inflammatory and cellular processes that caused the initial scarring are not fully eliminated. Recurrence typically manifests within two months of the initial PVR surgery, requiring close and continuous follow-up care.
Patients with PVR frequently require multiple surgical interventions to control the disease and achieve a stable retinal attachment. Long-term management involves monitoring for signs of new traction and utilizing the most effective tamponade agent to maximize the chance of a lasting anatomical and functional result.