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We removed preretinal membranes previously in contact with an intraocular silicone oil bubble from 22 human eyes for ultrastructural examination. All had membrane-bound intracytoplasmic vacuoles, which most likely had been filled with silicone oil before tissue processing. The vacuolation was more pronounced at the surface of the membrane. In the course of ingestion of silicone oil by preretinal cells, giant vacuoles may form by fusion of smaller vacuoles as these cells lack the ability to digest silicone oil.

In the aphakic eye, with intact iris diaphragm, silicone oil has frequently caused a pupillary block. In this situation aqueous humour accumulates behind the iris and forces silicone oil through the pupil into the anterior chamber. An iridectomy at the 6 o'clock position can effectively prevent this pupillary block. The iridectomy allows free passage of aqueous to the anterior chamber which remains free of silicone oil. No permanent contact with silicone oil and the cornea is established, and development of keratopathy is prevented. The effect of this iridectomy in 62 eyes with intact iris diaphragm in patients in Rotterdam (35 cases) and Nagoya (27 cases) is demonstrated. Only in 6.5% of the cases was silicone oil present in the anterior chamber at the end of the follow-up period of 7 months.

Two episodes of infection with epidemic methicillin-resistant Staphylococcus aureus (EMRSA) associated with silicone oil baths are described. In vitro studies indicated that certain organisms, including EMRSA, can survive in silicone oil for several days. We conclude that the oil acted as a reservoir for continuing infection in our patients. We suggest routine care of silicone oil baths in order to prevent cross infection.

We analyzed retrospectively 45 patients who had received silicone oil injection for vitreoretinal problems and divided them into three groups: aphakic patients who had undergone an extracapsular cataract extraction (AEC), aphakic patients who had undergone an intracapsular cataract extraction (AIC) and phakic patients (PHA). Patients were followed up from 4 to 13 months (average: 8.5 months). Irreversible silicone keratopathy was found in 50% of the eyes in the AIC group between 4 and 8 weeks postoperatively. An intact lens or capsule correlated well with the absence of this complication. In phakic eyes, secondary cataract was the most prominent early complication, developing by the end of the eighth week in 60% of eyes. Other early complications were inflammatory surface silicone membranes, rubeosis, iritis, glaucoma and capsular opacification.

The use of silicone oil as a retinal tamponade in the treatment of proliferative vitreoretinopathy is often complicated by membrane reproliferation. We studied the development of traction retinal detachments following the intravitreal injection of 15,000 retinal pigment epithelial cells in silicone-, perfluoropropane-, and fluid-filled rabbit eyes. By 28 days a higher proportion of silicone-filled eyes (83%) had severe proliferative vitreoretinopathy than either the perfluoropropane-filled (30%) or fluid-filled (10%) eyes. An in vitro proliferation assay using the vitreous samples showed that the silicone-filled vitreous had increased mitogenic activity for retinal pigment epithelial cells compared with the gas-filled or fluid-filled vitreous. Silicone oil appears to increase proliferation by stimulating the release of more or different mitogenic factors as well as by concentrating active factors into a smaller volume near the retina.

Out of 196 aphakic and 4 phakic eyes with silicone oil in the anterior chamber (all vitrectomized, postoperative follow-up 6 months to 5 years) we found 83 eyes (42%) with keratopathy. They present clinically and histologically as calcific band keratopathy (55 eyes) or diffuse bullous corneal edema (28 eyes). Time of onset, course and frequency in correlation to preoperative diagnosis are analyzed. Pathogenesis, prevention and therapy of keratopathy are discussed.

The results of silicone oil surgery in a consecutive series of 500 patients are reported. Special emphasis is given to anatomical and functional long-term results, postoperative glaucoma and keratopathy, and to the results following silicone oil removal.

We reviewed the results of silicone oil removal after vitreous surgery for recurrent retinal detachment with proliferative vitreoretinopathy in 55 eyes. The minimum follow-up period was six months. Retinal detachment recurred in five eyes (9%). Evidence of recurrent epiretinal membrane formation at the time of or after silicone oil removal was noted in 21 eyes (38%). Penetrating keratoplasty combined with silicone oil removal was successful in five of six patients. Mild corneal changes noted in ten eyes (18%) remained the same or cleared in seven eyes after silicone oil removal. Overall, postoperative visual acuity improved in 24 eyes (44%), remained the same in 18 eyes (33%), and decreased in 13 (24%). In 22 eyes without clinical evidence of silicone-associated complications at the time of silicone oil removal, postoperative visual acuity remained unchanged or improved in 20 (91%).

Silicone oil is now used with increasing frequency to treat cases of complicated retinal detachment (RD). The authors report their results using silicone oil in eyes with RD resulting from proliferative diabetic retinopathy (PDR) or proliferative vitreoretinopathy (PVR). The retina was completely reattached at last examination in 16 (70%) of 23 eyes with PDR and 20 (67%) of 30 eyes with PVR. Final vision of 5/200 or better was obtained in 5 eyes with PDR (22%) and 16 eyes with PVR (53%) (P = 0.0016). Reproliferation of epiretinal membranes occurred in 26% of diabetics and 23% of eyes with PVR. Silicone oil did not cause regression of iris neovascularization. Complications of silicone oil included corneal decompensation, lens opacification, intraocular pressure elevation, and hypotony.

A total of 42 cases (42 eyes) with silicone oil in the anterior chamber after pars plana vitrectomy (PPV) and after silicone oil injection into the vitreous cavity (SIV) were analyzed. The main complications caused by silicone oil were corneal endothelial cell damage and secondary glaucoma. Specular microscopy showed decreased cell density, apparent pleomorphism of endothelial cells, and increased corneal thickness. In some cases, edematous and necrotic endothelial cells were found. The characteristic optical artifacts resulting from silicone oil coming into contact with the endothelium, such as a bright reflex, reversed pattern of illumination, and interference fringes, were also observed. There was a definite correlation between elevated intraocular pressure (IOP) and the presence of silicone oil in the anterior chamber; the IOP dropped significantly on removal of the oil. The treatment and prevention of conditions involving silicone oil in the anterior chamber are briefly discussed.

The use of intravitreal silicone oil injection to separate preretinal membranes from the retinal surface in proliferative vitreoretinopathy (PVR) was pioneered in the United States. The anatomical results obtained were encouraging but complications of cataract, glaucoma and keratopathy frequently occurred. This method was therefore discontinued in the United States once the techniques of pars plana vitrectomy and membrane dissection had been developed. More recently, however, it has become clear that in severe PVR treated by vitrectomy procedures, recurrent traction is almost inevitable and prolonged vitreous substitution is required to limit the associated retinal detachment. Silicone has been selectively re-introduced for this purpose. Improved techniques and oil removal in some cases have reduced the incidence of complications. Insoluble gases have also been widely used in the United States to achieve the same objective but have generally been found to be less effective. The comparative merits of these alternative forms of vitreous substitution remain controversial. A randomized clinical trial is currently being conducted in the United States to address this issue. The trial embodies features of multicenter clinical trials used successfully in other prospective clinical studies. Silicone oil is still used less frequently than in Europe or in Japan for the management of diabetic traction detachment and giant tears.

The comparatively high refractive index of silicone oil significantly alters the refractive power of the human eye when it is placed into the vitreous cavity during retinal reattachment surgery. If cataract extraction and intraocular lens (IOL) implantation are subsequently performed, significant refractive errors result with most IOL styles if standard formulas are used to determine lens power. Thick-lens optical analysis of four IOL styles showed that the meniscus style yields the smallest difference between predicted (Binkhorst, Sanders-Retzlaff-Kraff formulas) and actual postoperative refraction. This IOL style also minimizes the change in refractive error that accompanies subsequent alterations in the contents of the vitreous cavity, including removal of silicone oil and replacement with balanced salt solution.

The results of a retrospective study of the effects of silicone oil removal from 85 eyes in 85 patients are reported. Pars plana vitrectomy and fluid/silicone oil exchange had been undertaken for retinal detachments associated with giant retinal tears or with proliferative vitreoretinopathy in all cases. Clinically significant cataract developed in 60% of lenses that were clear at the time of oil removal, and 85% of pre-existing lens opacities progressed. Removal of oil from 19 eyes with uncontrollable glaucoma was combined with drainage surgery in 14 eyes. Postoperatively the intraocular pressure was controlled in 13. Corneal decompensation either improved or was unchanged in eight out of nine patients after silicone oil removal, and three patients had penetrating keratoplasty and maintained a clear corneal graft. Patients who did not have glaucoma or keratopathy at the time of silicone oil removal did not develop these complications.