Sir,

We describe the histopathology of an epiretinal membrane (ERM) that developed after intraoperative use of perfluorocarbon liquids (PFCL: fully fluorinated compounds with high specific gravities1).

Case report

A 94-year-old man was referred to our unit with vision loss, right eye. Past ocular history included vitreous loss and ‘dropped nucleus’ during right eye cataract surgery. Examination revealed a visual acuity of 20/80 and rhegmatogenous retinal detachment. The fellow eye was unremarkable. He underwent three-port pars plana vitrectomy with vitreous base trimming, internal subretinal fluid drainage and endolaser. The PFCL perfluoroctane was used to assist surgery and was carefully removed afterwards. After fluid–air exchange, the eye was filled with perfluoropropane gas. Three months later, the patient represented with metamorphopsia and vision of 20/200 due to macular ERM. The ERM was microsurgically excised (residual PFCL was not noticed during this procedure) and was fixed in 10% neutral buffered formalin. After dehydration in graded concentrations of ethanol, it was embedded in paraffin wax.

Tangential sections through the specimen (stained with haematoxylin and eosin, periodic acid Schiff or an immunohistochemical technique to delineate various cellular elements) revealed epithelial and a few fibroblastic cells with little extracellular matrix. There was focal pigmentation. The epithelial cells contained slightly refringent material in variable-sized vacuoles, along with periodic acid Schiff-positive material that distends the cells. These vacuolated cells and the fibroblastic (metaplastic) cells exhibited the immunophenotypes of retinal pigment epithelial (RPE) cells, being positive for cytokeratin 7 and pan-cytokeratin (which recognises several different cytokeratins including 8/18), and negative for glial and macrophage markers (Figure 1).

Figure 1
figure 1

Sections through the excised ERM. (a) Section stained with the PAS method and counterstained with haematoxylin. The cells have a mixed epithelial and fibroblastic (metaplastic) phenotype, with many of the epithelial cells distended by vacuoles within PAS-positive cytoplasm (arrow). (b) Immunohistochemistry for cytokeratin 7 (red chromogen haematoxylin counterstain) demonstrate that the vast majority of the cells are of retinal pigment epithelial origin. (c) As in b but the section has been labelled for glial cells (using the glial marker glial fibrillary acidic protein: red chromogen haematoxylin counterstain). Glial cells are not seen but a focus of pigment is present (arrow). (d) Immunohistochemistry for the macrophage marker CD68pg (red chromogen haematoxylin counterstain) reveals only a few cells that express this marker in the membrane (arrow). All figures are at the same magnification: scale bar=100 μm.

Full size image

Comment

ERMs that occur following retinal detachment, that is, in proliferative vitreoretinopathy, are fibrocellular in nature with a mix of glial and RPE cells. To this ‘proliferative vitreoretinopathy reaction’ may be added a macrophagic foreign body response if a liquid tamponade agent is present.2 In our patient, the ERM had a markedly different microscopic appearance, with little extracellular matrix formation and grossly swollen RPE cells that appeared to contain tamponade agent (it was not possible to directly identify the intracellular material as PFCL). No glia were present and the typical foreign body response was also absent. Although a similar response has been reported following silicone oil use,3 it has not been reported after PFCL use. Indeed, because of their toxicity, these agents are not usually left in the eye following their use as intraoperative tools. Nevertheless, despite careful removal of residual PFCLs droplets, some may occasionally be retained in the vitreous cavity, and the unusual ERM appearance in our patient presumably reflects this situation. Interestingly, experimental subretinal injection of PFCLs results in phagocytosis of PFCL by RPE within 3 h of injection,4 which may help explain the appearances of the epiretinal RPE in our patient.