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Cataract Surgery

2008-09-13 Cataract extraction after silicone oil repair of retinal detachments due to necrotizing retinitis. Cataract is common after silicone oil repair of retinal detachment due to necrotizing retinitis in acquired immunodeficiency syndrome. Unpredictable refractions in the first 16 eyes prompted refinement of lens calculations and resulted in a reduction in refractive errors. Silicone Study To compare, through a randomized, multicenter surgical trial, the postoperative tamponade effectiveness of intraocular silicone oil with that of an intraocular long-acting gas for the management of retinal detachment complicated by proliferative vitreoretinopathy (PVR), using vitrectomy and associated techniques.The use of silicone oil and gas. The treatment of retinal detachment complicated by PVR remains controversial. Although some cases are managed successfully by pars plana vitrectomy and with temporary tamponade provided by intraocular gas, others eventually redetach with this technique. Preliminary reports indicate that prolonged tamponade with liquid silicone results in improved anatomical success, but the eventual visual outcome may be prejudiced by silicone-related complications, particularly glaucoma and keratopathy. The addition of hydraulic reattachment by simultaneous fluid/gas exchange to vitrectomy surgery has proved to be an important development. Although complications are few with these procedures, subsequent redetachment is frequent. The Silicone Study was a randomized trial to investigate the relative merits of silicone oil or gas as tamponade modalities. All study patients underwent vitrectomy and were randomized intraoperatively either to silicone oil or to gas. Two groups of eyes were entered into the study: eyes that had not had a prior vitrectomy (Group 1) and those that had undergone previous vitrectomy outside the study. A critical element in the study was a standardized surgical procedure for PVR. This surgical procedure, intended to relieve retinal traction with vitrectomy techniques, was followed by assessment of the relief provided by an intraocular air tamponade. The eye was randomized to silicone oil or gas only after completion of the entire surgical procedure to eliminate investigator bias that might develop through knowledge of the treatment modality. Patients were examined 5 to 14 days following the randomization and again at 1, 3, 6, 12, 18, 24, and 36 months after that date. Repeated surgery was permitted for either treatment modality. The Fundus Photograph Reading Center staff processed and analyzed photographs taken at all the clinics, graded the preoperative severity of PVR on the basis of baseline visit photographs, and confirmed the macular status at followup visits. The Silicone Study Group: Proliferative vitreoretinopathy [Editorial]. Am J Ophthalmol 99: 593-595, 1985.A 3-step modification of intraocular lens calculations is recommended: (1) use of specific sound velocities to calculate axial length; (2) use of convexoplano lenses; and (3) addition of a constant to the lens power to compensate for the refractive index of silicone oil. Good surgical technique and accurate lens calculations should improve management of cataracts that arise after retinal detachment repair with silicone oil in patients with acquired immunodeficiency syndrome. Keywords: Adult AIDS-Related Opportunistic Infections/COMPLICATIONS Cataract/*ETIOLOGY Child Cytomegalovirus Retinitis/COMPLICATIONS Female Human Lenses, Intraocular Male Middle Age *Phacoemulsification Postoperative Complications Retinal Detachment/ETIOLOGY/*SURGERY Retinal Necrosis Syndrome, Acute/*COMPLICATIONS *Silicone Oils A total of 151 eyes were randomized to receive either gas or silicone oil. Four hundred and four eyes were randomized to receive either gas or silicone oil. In the Silicone Study, anatomic and vision results and prevalence of complications suggest that the differences in outcomes between Groups 1 and 2 were not as great as previously believed. Intraocular pressure (IOP) abnormalities were a common postoperative complication in eyes with PVR. Chronically elevated IOP was found in 5 percent of the eyes; chronic hypotony was found in 24 percent of the eyes. Chronically elevated IOP was more prevalent in silicone oil eyes than in gas eyes. Chronic hypotony was more prevalent in C gas eyes than in silicone oil eyes, more prevalent in eyes with anatomical failure, and correlated with poor postoperative vision, corneal opacity, and retinal detachment. The presence of diffuse contraction of the retina anterior to the equator should alert the vitrectomy surgeon that the eye is likely to be hypotonous postoperatively. Retinotomy in the Silicone Study: Using data from the Silicone Study, we compared the cohort of eyes that underwent relaxing retinotomy with the cohort of eyes that did not in regard to preoperative and intraoperative findings and to visual and anatomic outcomes and complications. We concluded that eyes undergoing vitreous surgery for the first time for the treatment of PVR can be treated successfully in most instances by conventional techniques without the need for relaxing retinotomy. Retinotomy may be required more frequently in patients undergoing repeat vitreous surgery for PVR. In those patients, silicone oil and gas appeared to be equally effective tamponade modalities. In eyes undergoing retinotomy that have not been previously vitrectomized, silicone oil may initially increase the likelihood of visual success and may decrease the likelihood of hypotony at 6 months; however, long-term observations at 24 months suggested a trend toward worsening in silicone oil-filled eyes and improvement in gas-filled eyes. Outcomes After Silicone Oil Removal: Because the advisability of silicone oil removal from these complex eyes remains controversial, we used data from the Silicone Study to compare visual and anatomic outcomes in the cohort of eyes from which oil was removed with visual and anatomic outcomes in the cohort of eyes in which oil was retained. Compared with the oil-retained eyes evaluated at a comparable time after silicone oil injection, oil-removed eyes at the examination before oil removal were more likely to have attached retinas, have visual acuity 5/200, and not be hypotonous. Eyes with attached retinas at the time of oil removal generally showed improvement in visual acuity at the last followup examination. In a matched-pair cohort analysis comparing oil-removed eyes with oil-retained eyes, there was an increased risk of recurrent retinal detachment at the last followup examination in the oil-removed eyes. However, in oil-removed eyes with attached retinas at the last followup examination, overall visual acuity improved and the incidence of complications decreased. Corneal Abnormalities in the Silicone Study: The Silicone Study was the first study to document that the postoperative incidence rates of corneal abnormalities are equivalent between oil and gas. The incidence of corneal abnormalities in eyes randomized to gas was higher than expected, and the incidence of corneal abnormalities in eyes randomized to silicone oil remained high in spite of the use of an inferior iridectomy. Successful surgical repair of the retinal detachment with a single operation and prevention and early management of silicone oil-corneal touch should help to prevent corneal abnormalities. If rubeosis iridis or severe aqueous flare is present, preoperative treatment with intense topical and possibly periocular steroids might help to reduce preoperative and postoperative inflammation, which may mediate corneal damage. Postoperative Macular Pucker in the Silicone Study: Macular pucker is a term that describes wrinkles and folds in the central retina resulting from contraction of an epiretinal membrane. A limited manifestation of PVR, macular pucker is observed within 6 months in 4 to 13 percent of eyes after successful conventional surgery for retinal detachment without PVR. Using data from the Silicone Study, we found that the 6-month point prevalence rate of postoperative macular pucker was 15 percent. The occurrence of macular pucker following successful surgery for retinal detachments complicated by severe PVR was not influenced by the choice of intraocular tamponade. Prognosis Using the Silicone Study Classification System: As part of the study, a Silicone Study classification system for PVR was developed based on the characteristic patterns of retinal distortion produced by the contraction of proliferative membranes on the retina or within the vitreous base. This classification was designed to document the extent and anatomic distribution of PVR present preoperatively and to help standardize the surgical treatment. Using data from the Silicone Study, we demonstrated that identification of the anteroposterior extent of the PVR was prognostic of visual acuity and hypotony at 24 months. The joint knowledge of the location of PVR (using the Silicone Study classification system) and the tightness of the funnel for retinas with 9 to 12 clock hours involved by fixed folds (using the Retinal Study classification system) has prognostic utility for eyes presenting with anterior plus posterior PVR. Comparison of Outcome in Anterior Versus Posterior PVR in the Silicone Study: Using the Silicone Study classification system, we compared preoperative and intraoperative findings, and vision and anatomic outcomes and complications, in the cohort of eyes with anterior PVR and the cohort of eyes with only posterior PVR. We found that anterior PVR was more prevalent in these Silicone Study eyes than was posterior PVR and had a worse prognosis. Eyes with anterior PVR and clinically significant posterior PVR changes had a better visual prognosis if silicone oil rather than gas was used. Long-Term Outcome in the Silicone Study: At the time of study closeout (June 30, 1991), the National Eye Institute funded an extension of the Silicone Study to provide long-term followup in the cohort of eyes (randomized to silicone oil or long-acting gas) with attached maculas at the 36-month followup examination. During 6 years of followup, attachment of the macula was maintained for all eyes. No significant differences in the rates of complete retinal attachment, visual acuity greater than 5/200 or glaucoma were found between treatment groups. In contrast, gas-treated eyes had more hypotony. Success in the first operation for PVR is paramount in obtaining better visual results. Overall, surgery for PVR had a high likelihood of retinal reattachment, and if anatomically and visually successful at 3 years, there is an excellent chance that the results will be maintained over the long term.