The adherence of silicone oil to standard and heparin-coated PMMA intraocular lenses

During combined cataract extraction and intraocular lens insertion in eyes undergoing removal of silicone oil, we noted that oil became adherent to the implant. This adhesion persisted post-operatively. Although patients seemed not to be symptomatic as a result of this effect, the oil interferes with the fundal examination. Since heparin-coated intraocular lenses are more hydrophilic than unmodified lenses, oil should spread less well on these lenses and therefore be less adherent. This study was conducted to test this hypothesis. Heparin-surface-modified and unmodified polymethylmethacrylate (PMMA) lenses were immersed in 1000 centistoke neat silicone oil and in an emulsion of silicone oil taken from a patient. The lenses were washed with saline solution in an attempt to remove adherent oil. The lenses were photographed for examination and qualitative comparison. It was found that both neat and emulsified silicone oil was strongly adherent to both surface-modified and unmodified lenses, and could not easily be washed off. The heparin-coated lenses showed a tendency for adherence of emulsified oil. It is concluded that heparin coating of intraocular lenses does not prevent, though may reduce, oil adherence. We recommend that care be taken to avoid contact between oil and implant during combined oil removal and cataract extraction.link_to_subscribed_fulltex

Pathobiology of epiretinal and subretinal membranes: Possible roles for the matricellular proteins thrombospondin 1 and osteonectin (SPARC)

Epiretinal and subretinal membranes are fibrocellular proliferations which form on the surfaces of the neuroretina as a sequel to a variety of ocular diseases. When these proliferations complicate rhegmatogenous retinal detachment (a condition known as proliferative vitreoretinopathy or PVR), the membranes often contain numerous retinal pigment epithelial (RPE) cells and a variety of extracellular proteins. The extracellular proteins include adhesive proteins like collagen, laminin and fibronectin. In addition, several matricellular proteins with potential counter-adhesive functions are present in the membranes. Two such matricellular proteins, thrombospondin 1 and osteonectin (or SPARC: Secreted Protein Acidic and Rich in Cysteine), tend to be codistributed with the RPE cells in PVR membranes. By virtue of their counter-adhesive properties, thrombospondin 1 and SPARC may reduce RPE cell-matrix adhesion and so permit key RPE cellular activities (for example, migration or shape change) in periretinal membrane development. Furthermore, within a 'cocktail' containing other proteins such as the metalloproteinases and growth factors like the scatter factor/hepatocyte growth factor family, matricellular proteins may play a role in the RPE cell dissociation from Bruch's membrane, which characterises early PVR.link_to_OA_fulltex

Challenges in ophthalmic pathology: The vitreoretinal membrane biopsy

The introduction of vitreoretinal microsurgery has produced a new type of biopsy; that of the vitreoretinal membrane. This review investigates methods by which these scar-like tissues are handled in the laboratory and explores the implications of the results of such evaluations. The study of vitreoretinal membrane biopsies has provided much information concerning the pathobiology of the various conditions which may give rise to the tissue as well as insights into how membranes themselves develop. Moreover, the application of new laboratory techniques is expected to enhance our understanding of the formation of vitreoretinal membranes, and lead to further advances in their surgical and medical management.link_to_subscribed_fulltex