Kor J Ophthalmol Vol.20, No.2, 2006 cataract. Therefore, in these cases, lens-sparing vitrectomy should be avoided. In addition, Maguire and Trese24 reported that cataracts developed in two out of three eyes with stage 5 ROP after lens-sparing vitrectomy. The presence of plus disease in stage 4 and stage 5 ROP is also a predictor of poor surgical outcome.23 There is a wide range in the severity of the disease,31 so we created a division between moderate cases and those of a more severe degree. The severity of plus disease may not influence the surgical outcome, but its presence may be rather important by itself. All cases in this study exhibited progressive retinal detach- ment with plus disease in spite of previous treatment with laser photocoagulation. This is, in part, a cause of the failure of retinal reattachment and intra- or post-operative vitreous hemorrhage. If our study patients had had a lower incidence of plus disease, our surgical outcomes would have very likely been better. Glaucoma and vitreous hemorrhage were both reported to be causes of poor outcomes in severe ROP.19,36 Our results also revealed retinal reattachment failure after lens-sparing vitrectomy in cases that also had such compli- cations. To avoid this, lens-sparing vitrectomy should be performed before stage 5 ROP develops, and also in the absence of plus disease. If the plus disease presents as a severe condition, there will be a higher probability of intra-operative and post-operative complications, and the surgical prognoses should be guarded. Luna et al.37 reported that peripheral retinal laser photocoagulation before lens-sparing vitrectomy for stage 4a ROP eyes affected surgical outcomes. Without laser photo- ablation before surgery, the organized vitreous was easier to cut and the retina was less rigid and could be smoothly flattened. Conversely, with pre-surgical laser photoablation, the organized vitreous became more difficult to manipulate, and the retina became more rigid. All the members of our study had undergone laser photocoagulation before surgery, so our study cannot speculate on the differences observed by the previous study. The observation by Luna et al. may or may not be true, but the difficulty of surgical manipulation and the retinal rigidity seem to depend more on the fibrovascular proliferative changes of the detached retina than on any pre-operative procedure. In the treatment of stage 5 ROP, the lens-sparing vitrectomy produced less-than-desirable results, but in the treatment of stage 4a or stage 4b ROP, the lens-sparing vitrectomy yielded rather promising results. However, several limitations of this study should be noted. One is the small case number of our study. The second limitation is that we could not standardize the gestational age and birth weights of our subjects. Further studies with a larger number of patients are required in order to determine the timing and criteria for surgery to treat stage 4 ROP, and also to decide which surgical technique is the most desirable for treatment of stage 4 and stage 5 ROP. In summary, we described the results of lens-sparing vitrectomy as a treatment for stage 4 and stage 5 ROP. Surgical outcomes for stage 4 ROP produced better 116 post-operative results than those for stage 5. Some cases manifested such post-operative complications as cataracts, vitreous hemorrhages, glaucoma, and the formation of retinal breaks. These results demonstrate that while lens-sparing vitrectomy may be beneficial in cases of stage 4 ROP, it is certainly not without risk of complications. References 1. Ng EY, Connolly BP, McNamara JA, et al. A comparison of laser photocoagulation with cryotherapy for threshold retinopathy of prematurity at 10 years: Part 1. visual function and structural outcome. Ophthalmology 2002;109: 928-35. 2. 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