Immunohistochemical characterization of sub retinalmembranes (SRMs) in proliferative vitreoretinopathy

Purpose: To provide immuno histo chemical characterization of sub retinal bands removed during retinal surgery in eyes with proliferative vitreo retinopathy (PVR). Methods: This study included all eyes with the clinical diagnosis of PVR that underwent pars plana vitrectomy surgery during which the subretinal tissue causing retinal detachment was obtained. The subretinal bands were removed “en bloc” through retinotomy using subretinal intraocular forceps. The excised tissue was sent for histopathologic analysis. Immunohistochemistry (IHC) was performed to confirm the cellular nature and components of these subretinal membranes. The IHC stains included, glial fibrillary acidic protein (GFAP), Pancytokeratin, CD3 CD20 CD68 and CD34. Results: Subretinal membranes (SRMs) from 7 eyes were included in the analysis. All cases had successful surgical outcome with reattachment six months after surgery. The microscopic examination of the excised tissue nicely demonstrated the constituents of the SRM as follows: retinal pigmented epithelial (RPE) cells that stained positively with cytokeratin (7/7), avascular plaques of RPE cells showing metaplasia in the form of spindle cells (7/7). Fragments of gliotic GFAP-positive neural retina was adherent to the fibrous plaque (6/7). Bruch’s membrane was identified in one specimen. CD68 positive macrophages were seen in (5/7) being silicon oil- laden macrophages in2/5. Rare CD3 positive cells were also noted in 1 specimen. Conclusion: Subretinal bands in PVR are mainly composed of reactive avascular plaques of RPE metaplasia and macrophage infiltration. The overlying gliotic retina or Bruch’s membrane are likely to be adherent to such plaques and might be inadvertently excised during removal of such membranes. Removal of SRMs is essential for successful reattachment of the retina.