· AIM:To study the effect of external route microsurgery for giant retinal tear(GRT)caused by vitreous incarceration in the inner aspect of sclerotomy sites during or after vitrectomy.· METHODS:From June 2008 to February 2010,12 cases of patients with GRT related to vitreous incarceration of sclerotomy were treated using external route microsurgery and analyzed retrospectively.The encircling,silicone buckle,transscleral cryopexy and perfluorapropane tamponade were performed under a surgical microscope.Among them,4 cases of GRT were treated intraoperatively and 8 cases were occurred and treated postoperatively.· RESULTS:The following up time ranged from 2 to 15 months(mean 6 months).The retinas were reattached in eleven eyes after one operation.The retina was redetached in one eye one month later and another microsurgery was performed.At last,retinal reattachment was achieved in all patients.The postoperative best-corrected visual acuity was lower than 0.1 in 4 eyes(33%),0.1-0.3 in 5 eyes(42%)and higher than or equal to 0.4 in 3 eyes(25%).· CONCLUSION:The GRT related to vitreous incarceration of sclerotomy is a serous surgical complication.It is a secure and effective technique that the encircling,silicone buckle,tranascleral cryopexy and perfluorapropane tamponadd are used to treat the complication under the surgical microscope.·