| Pars plana vitrectomy methods are used to treat various types of posterior diseases, and surgery is often required in phakic as well as in aphakic and pseudophakic eyes. Serious posterior segment complications are infrequent, and the most common postoperative complication is later progressive lens opacity. To keep the patient's eyesight, we must try to keep the crystalline lens clear. But it is very common that the lens lose it's clarity after operation. The mechanism can not be confirmed at the moment. We studied an expanded series of these patients with a follow-up of 6 months in order to evaluate the incidence of postoperative cataract in patients of different ages and in groups of eyes in which different compositions of intraocular replacements were used. Such as : 18% perfluoropropane(18%C3F8) gas, silicon and BSS fluid.The patients were from the number two hospital of JiLin university who were in hospital from 2001-5 to 2003-10.We reviewed 103 consecutive records of posterior segment diseases in phakic eyes, which had been treated by vitrectomy. The patients had no history of previous ocular surgery and no known other ocular diseases. Only patients with an intact crystalline lens in both eyes were included, thereby permitting comparison between both lenses of the same patient. One 14-year-old boy was excluded because of long-term high-dose corticosteroid therapy for a separate systemic condition. The patient developed posterior subcapsular cataracts in both eyes because of the corticosteroids, thereby masking any possible effect of vitrectomy. Two other patients were excluded because the minimum of six months of follow-up could not be obtained. Thus, the study population was 100 patients(100 eyes). We divided the 100 patients into two groups:≥50 years old (53 persons) and ＜50 years old (47 persons).During the operation BSS were used as irrigating fluid. There were 29 patients who used silicon as the intraocular replacement,48 patients used 18%C3F8,23 patients used BSS fluid. Postoperative lens status was determined using the Lens Opacities Classification System Ⅲ (LOCSⅢ).The LOCSⅢ system has been shown to have excellent intra-observer agreement and to give results comparable to objective lens grading systems. Under this system, color slit-lamp photographs with the slit beam oriented at 450 and the camera focused on the center of the lens were taken by trained photographs. Of the patients aged 50 or above 50 years old the rate of occurrence of cataract formation after pars plana vitrectomy is 73.58%,of the patients under 50 years old the rate of which is 42.55% (P﹤0.05).The rate of occurrence of cataract formation in patients who use 18%C3F8, silicon and BSS fluid to replace the vitreous after pars plana vitrectomy is 52.08%, 82.76% and 43.48% respectively( P﹤0.05).The result showed that cataract formation after pars plana vitrectomy was relate to the patients' ages. The older the patients were, the higher the rate of occurrence of cataract formation. The style of the postoperation cataract was related to the patients' ages and the composition of the intraocular replacements. If the patients was older than 50, it was easy to suffer from nuclear sclerotic cataract after vitrectomy. However posterior subcapsular cataract was often seen in patients who used 18%C3F8 as intraocular replacement after pars plana vitrectomy. Cataract formation after vitrectomy was also relate to diseases after operation, such as high intraocular pressure, uveitis et al. Cataract formation after vitrectomy was also relate to the operation itself. There were at least three possible mechanisms proposed: intraoperative light toxicity, intraoperative oxidation of lens proteins, and surgery-induced changes of the lens'biochemical microenvironment.Conclusion: Cataract formation after vitrectomy was relate to the patients'ages and the composition of the intraocular replacements. Using silicon as intraocular replacement after pars plana vitrectomy tends to develope lens opacity mostly. Diseases after th...
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