Although rare and mostly benign, allergy to HA should be included in the differential diagnosis when chemosis, proptosis and restriction of eye movements occur after parabulbar or retrobulbar anaesthesia. The authors feel that the beneficial effect of HA in small volumes of RA warrants its use despite this potential complication.

SUMMARYThe modes of action of topical cyclosporin A were studied in rabbits. Immunorejection of corneal allografts was provoked by placing the grafts eccentrically, in contact with the limbus. Topical application of cyclosporin A five times daily for 28 days prevented the rejection of corneal allografts. All grafts were rejected in the control animals. The seven rabbits of the cyclosporin A group were subsequently treated for six months with a lower dosage of cyclosporin A 1%. In six rabbits the graft remained clear. One rabbit treated with two drops a day showed an allograft reaction that could be suppressed by increasing the dosage. After six months, discontinuation of the therapy resulted in rejection of all grafts within four weeks. Cyclosporin A could be detected in the plasma and aqueous humour of both eyes at the end of the treatment, raising the question whether the immunosuppressive effect of topically applied cyclosporin A was due to local or systemic action. Cyclosporin A 1% was therefore applied to the fellow eye five times daily following transplantation, and this treatment, producing similar plasma levels of cyclosporin A, failed to delay the rejection of eccentric corneal allografts. Consequently the suppression of the allograft rejection by topical cyclosporin A is primarily a local immunosuppressive effect, though systemic influence is not ruled out.

Circulating fibrocytes and their dendritic derivatives are a new aspect of FECD that deserves further investigation. Because they are known to cause fibrosis in a variety of organs, they may play a similar role in FECD and might be a valuable target for nonsurgical therapy.

Using in situ immunohistochemical techniques and a broad panel of antibodies directed against intermediate filament proteins, vascular endothelial markers, neuroectodermal/neuroendocrine markers, and monoclonal antibodies raised against human corneal endothelial cells (HCECs), a comparative phenotypical analysis was performed on HCECs, keratocytes, trabecular cells, and cells lining the canal of Schlemm. The coexpression of cytokeratins and neurofilaments by HCECs argues in favor of a neuroectodermal origin, which is further supported by the fact that they stain positive for neuron-specific enolase (NSE) and that they express neural cell adhesion molecules (N-CAM) at their surface. The expression of NSE and N-CAM also applies to the trabecular cells. The cells lining the canal of Schlemm were found to share many immunophenotypical features with vascular endothelial cells (i.e., factor-VIII-related antigen and BMA-120), rather than with HCECs. This was further supported by the reactivity of two monoclonal antibodies (i.e., 9.3 E and 5.52 H) that were raised against HCECs, and which labelled vascular endothelium and cells lining Schlemm's canal.