Proliferative vitreoretinopathy (PVR) is the formation of scar tissue on the surface of the retina and within the vitreous cavity, the gel-like substance that fills the eye. This condition is a complication that most often arises after a retinal detachment or the surgery to repair it. As this scar tissue contracts, it pulls on the retina, which can cause it to detach again. PVR is the most common reason that retinal reattachment surgery fails.
Development and Progression of PVR
The development of PVR is an abnormal wound-healing response inside the eye, often triggered by a retinal tear, surgery, or significant trauma. These events disrupt normal barriers within the eye, allowing cells like retinal pigment epithelial (RPE) and glial cells to migrate into the vitreous cavity and onto the retinal surface.
Once on the retina, these cells multiply, driven by growth factors and inflammatory signals from the initial injury. As the cells proliferate, they produce extracellular matrix components, forming fibrous membranes that adhere to the retina. Over time, these membranes mature and contract, much like a scar on the skin.
This contraction exerts a pulling force on the retinal tissue, which can cause wrinkles, folds, or new tears, leading to a recurrent retinal detachment. The severity of PVR is classified into grades to help surgeons plan treatment. These include Grade A (minimal changes), Grade B (wrinkling of the inner retinal surface), and Grade C (full-thickness retinal folds). Advanced stages are characterized by fixed, stiff folds in the retina, making repair more challenging.
Symptoms and Diagnosis
The symptoms of PVR can appear gradually or suddenly and often mimic those of a primary retinal detachment. Patients may experience a decrease in vision that is blurry or distorted, a phenomenon known as metamorphopsia. The appearance of new floaters, which look like spots or webs, or seeing flashes of light are also common complaints.
Because PVR frequently develops after surgery to repair a retinal detachment, an indicator for patients is worsening vision in an eye that had been improving. This change signals that a new problem is occurring. The condition can lead to a loss of peripheral vision, and if the macula becomes involved, it can cause the loss of detailed central vision.
An ophthalmologist diagnoses PVR through a comprehensive eye examination. A dilated fundus exam, where the pupil is widened, allows the doctor to look at the retina and identify scar tissue membranes, wrinkling, or detachment. If the view of the retina is blocked, a B-scan ultrasonography is used. This imaging technique uses sound waves to create an image of the eye’s internal structures, revealing the extent of the membranes and detachment.
Surgical Management
The primary treatment for PVR is a surgical procedure called a pars plana vitrectomy. The goal of this operation is to relieve the traction on the retina caused by scar tissue and reattach it to the back of the eye. The surgery is performed through tiny incisions in the sclera, the white part of the eye.
During the vitrectomy, the surgeon first removes the vitreous gel from the eye. This eliminates the scaffold upon which scar tissue can grow and provides better access to the retinal surface. The next step is the membrane peel, where the surgeon uses micro-forceps to meticulously peel away the contractile membranes from the retina, taking great care not to cause new tears in the delicate tissue.
Once the membranes are removed, the surgeon flattens the retina against the back of the eye. To hold the retina in place while it heals, an internal tamponade agent like a gas bubble or silicone oil is injected into the eye. A scleral buckle, a flexible band placed around the eye, may also be used with the vitrectomy to increase the chances of successful reattachment.
Recovery and Prognosis
If a gas bubble is used as a tamponade, the patient must maintain a specific head position, often face-down, for several days to weeks. This positioning ensures the bubble presses against the correct area of the retina to support it as it heals. The gas bubble is absorbed by the body over time and replaced by the eye’s natural fluid.
In cases where silicone oil is used, strict head positioning is generally less of a concern. However, silicone oil does not dissolve on its own and needs to be removed in a second surgical procedure months later. The oil can provide longer-term support for the retina in complex cases.
The prognosis for visual recovery is guarded and often slow. The final visual acuity a patient achieves depends on the severity of the PVR and whether the macula was detached. Even with successful reattachment, vision may not return to its previous level, and some distortion can remain. PVR also has a chance of recurring even after successful surgery.