الفهرس 
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Abstract
PPV, combined with intraocular silicone oil tamponade, has become a relatively common technique for ”the repair of complicated retinal detachments since first introduced by Cibis in 1962 (Larkin et af., 1998).
The use of silicone oil as a long retinal tamponade has improved the
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chances of reattaching the retina in complicated cases of retinal detachment.
Unfortunately, the presence of intraocular silicone oil is associated with several complications, the commonest of which is cataract formation occurring in up to 100% of eyes retaining silicone oil for 6 months or more (Franks et af., 1991).
Cataract surgery in silicone filled eyes is complicated and requires modification in the surgical technique. Many difficulties are encountered when operating on these eyes. These difficulties may be encountered preoperatively as assessing the status of the retina and calculating the IOL power. Assessment of the status of the retina is a mandatory step prior to surgery. This, should determine whether the silicone oil will be removed or not during surgery. This is best done by the vitreoretinal surgeon operating on the original pathology (Coombes and Gartry, 2003).
Biometry is substantially altered by silicone oil tamponade within the posterior segment. Significant postoperative refractive errors may result because the echographically measured AL in eyes containing silicone oil is greater than the true AL. This is because the speed of sound in silicone oil (987m/s in silicone oil of viscosity 1000 centistokes) is slower than in vitreous humor (l532m/s). Different methods have been proposed to correct this error (Hoffer, 1994). Recently, non invasive optical biometry (The IOL Master) and lenstar are used (Hofzer et af., 2009).
Summary
The choice of IOL design and material needs careful consideration, palticularly if the oil is not removed. Lenses with an optic constructed of silicone should be avoided if contact with silicone oil may occur. Large diameter 10L with no positioning holes and a plano posterior surface is preferred (Ryan, 2006).
Intraopertively, small pupil and unstable zonules often coexist but they can usually be dealt with. The absence of the vitreous base, fluctuation of the ACD and movement of the lens-iris diaphragm may be a problem during phacoemulsification. This is parti~ularly important becaus~ the flaccid posterior capsule can then become aspirated and damaged (Coombes and Gartry, 2003).
Removal of the oil can be combined with phacoemulsification (Baer et al.,1995). There are various techniques of combined phacoemulsification and silicone oil removal (Tanner et al., 1998). One of these techniques is pars plana evacuation of silicone oil either before phacoemulsification or after its completion (Gonvers et a., 1985).
Another techniques is transpupilllary passive floatation of silicone oil through planned posterior capsulorrhexis and corneal wound following phacoemulsification and before IOL implantation (Assi et al., 2001)
Silicone oil removal is a procedure that carries a definite risk of serious complications as RD, keratopathy, hypotony, rubeosis irides and other complications. The incidence of these complications vary considerably (8-40%) (MeCuen et al., 1985).
Postoperatively, recurrent retinal detachment may occur following cataract extraction in eyes that have previously undergone PPV, and this is probably most common in those that have had an ICCE performed. Patients with previous retinal detachment treated with vitrectomy need be observed carefully.