Kor J Ophthalmol Vol.20, No.2, 2006 Lens-sparing vitrectomy in infants has been performed in the treatment of several diseases, and its main advantage is the phakic condition that results during visual rehabilitation after surgery.23-27 Lensectomy-vitrectomy produces an aphakic condition that can limit visual development during a critical period of development in infants. Scleral buckling surgery results in a myopic shift and necessitates additional surgery for buckle removal.28,29 Recently, several reports have shown that lens-sparing vitrectomy was effective in treating stage 4 ROP.30-32 Although lens-sparing vitrectomy appears to have some advantages, there is little available literature about the outcomes of this surgical technique and concerning complications from the treatment of stage 4 and stage 5 ROP. The purpose of this retrospective study is to describe the results of lens-sparing vitrectomy in the treatment of retinal detachment of stage 4 and stage 5 ROP. Materials and Methods Seventeen patients at Seoul National University Children’s Hospital between 1999 and 2003 with stage 4 (subtotal retinal detachment) and stage 5 ROP (total retinal detachment) and with plus disease who had undergone a lens-sparing vitrec- tomy in at least one eye were included in this study. All patients had been treated with laser photocoagulation of the avascular retina for threshold ROP, but they had not regressed. The inclusion criterion of patients with stage 5+ ROP in the present study was a posterior total tractional retinal detachment that resulted from the progression of rush-type ROP with plus disease, i.e. the vascularized retina was limited within the zone I area. The surgical technique for the lens-sparing vitrectomy for ROP has been described by Maguire and Trese.33 Surgery was complete when as much of the tractional membrane as possible was removed without an injury to the lens and when the entire retina was finally free from the traction. At the end of surgery an intravitreal air injection was performed for maintaining eyeball pressure, but a gas tamponade or silicone oil injection was not given. Postoperatively, spontaneous reattachment of the retina was periodically examined. The patients with bilateral symmetric ROP disease (i.e. with the same stage and severity of plus disease in both eyes) had undergone a lens-sparing vitrectomy in one eye and a scleral buckling surgery or lensectomy-vitrectomy in the other. Both eyes underwent surgery, either simultaneously or consecutively, within several days in accordance with the systemic condition of each patient. The patients with stage 4 or stage 5 ROP with plus disease in one eye and regressed ROP in the other eye had undergone a unilateral lens-sparing vitrectomy. Data from the eyes that had undergone a lens-sparing vitrectomy only were analyzed. Stages of ROP were defined in accordance with the international classification of ROP34 and plus disease, i.e., vascular dilation and tortuosity in the posterior pole. Patients were also subdivided into groups of both a moderate and a 114 severe degree, in accordance with the severity of the plus disease. A moderate degree of plus disease was defined as grade 4 vascular dilation and tortuosity by Wallace et al.35 A severe degree of plus disease was characterized by more severe vascular dilation and tortuosity than was seen in grade 4. Informed consent was obtained from the parents of all participants before sedation for examination and surgery. A review of the pre-operative clinical findings, post- operative results, and any complications was performed, and the results of the lens-sparing vitrectomy were compared in accordance with the stages. Anatomical success was defined as an attachment of the retina, at least in the posterior pole, during the post-operative follow-up periods. For the evalua- tion of visual development at the last follow-up, vision was classified into three categories: form vision (patients can fix their eyes on a small moving toy), light follow (patients can fix their eyes on a moving pen-light), and light perception (patients can differentiate between the light on and off ). Results Seventeen patients comprised the study population, and ten of the patients were females. The mean gestational period was 28.8 weeks (range: 25-34 weeks) and the mean birth weight was 1224 grams (range: 800-1870 grams). The mean post-operative follow-up period was 2.2 years (range: 1.1-4.8 years). The eight bilateral symmetric patients underwent a lens-sparing vitrectomy in one eye. Among them, three patients had scleral buckling surgery while the other five had the lensectomy-vitrectomy in the other eye. The nine unilateral patients underwent a lens-sparing vitrectomy in only one eye. Their other eyes had regressed without retinal detachment, which was resultant from the laser photocoagulation. Pre-operative stages of ROP and post-operative results are summarized in Table 1. At the last follow-up examination, visual development was assessed in ten eyes in which the retina was post-operatively attached. Form vision was seen in six of these eyes, light follow was noted in three eyes, and no light perception was found in one. None of the eyes in which the retina was not attached had light perception. Among the 17 cases of lens-sparing vitrectomy, cataracts and dense vitreous hemorrhages occurred as a post-operative complication in three patients. Two of these patients required lens surgery due to dense cataracts, and the remaining one patient did not require surgery but experienced mild lens opacity. Three occurrences of dense vitreous hemorrhage were observed, and they all resulted in a failure of the retina to reattach. In one of the unilateral patients, a retinal break was noticed during surgery which caused a failure of retinal reattachment. Two patients with stage 5 ROP experienced the post-operative complication of angle-closure glaucoma. The overall anatomical success rate was 58.8% (10/17), and the post-operative results of stage 4 ROP patients were