Introduction: In the late stages of proliferative diabetic retinopathy (PDR) the vascularized posterior cortical gel (PCG) contracts leading to a partial posterior hyaloidal separation, hemorrhage, and traction retinal detachment (TRD). "Additional epiretinal membranes" have been described previously. These are thin, usually transparent epiretinal membranes which extend anteriorly from the point of attachment of the elevated posterior cortical gel to the edge of the TRD. The origin and frequency of the occurrence as well as the clinical significance of such additional epiretinal membranes are the subjects of controversy.
Purpose: To quantitate the authors' clinical impression that additional epiretinal membranes are common in advanced PDR, to characterize them immunohistochemically, and to demonstrate the rationale for the authors' surgical approach.
Methods: Intraoperative observations for all patients undergoing diabetic vitrectomy and delamination over the last 2 years were reviewed retrospectively. The presence of additional epiretinal membrane was searched for in the initial stages of vitrectomy. When identified, their apparent continuity with the elevated portion of the PCG was confirmed. Surgical specimens were obtained from nine patients for immunohistochemical study.
Results: Additional epiretinal membranes were observes in 145 (81%) of 179 consecutive eyes with PDR that underwent surgery for macular TRD. Immunohistochemical staining with type II collagen antibody was positive in all specimens, suggesting that these membranes were of vitreous origin.
Conclusions: It is likely that the additional epiretinal membranes represent the posterior leaf of a split PCG, the anterior leaf being the elevated portion of the PCG. The two leaves remain fused in the main, fibrovascular portion of the epiretinal membrane. These findings help explain the clinical experience that once the posterior leaf of the PCG is identified and elevated, it provides an accurate point of entry into the surgical plane facilitating delamination of the fused (vascularized) portion of the PCG from the detached retina.