Objective    To explore the safety margin of harvesting limbal stem cells autograft from fellow eye.     Methods    The corneas of lagophthalmus divided into 7 groups according to the angle of harvesting ranging from 30°  to 210°  at stepwise increment of 30°. The three clinical indexes including opacity

fluorescein staining

neovascularization of corneas were observed at the end of 1

st

week

2

nd

week and a month postoperatively

the imprint cytology of corneal epithelium and HE staining were used to observe phaenotype and pathologic changes of corneal epithelial cells.     Results    When the angle of harvesting limbal stem cells autograft exceeded 150°

the corneal opacity

pe

rsistent corneal epithelial defect

corneal new vessels started to emerge (Rank test

P0.01). The imprint cytology showed the corneal cells was positive for PAS staining. The decreased layers of limbal epithelial cells and corneal new vessels could be manifested by histopathologic examinations.     Conclusion    The safety margin of harvesting limbal stem cells autograft was smaller than or equaled to 150°. If the angle exceeded 150°

the decompensations of limbal stem cells could not be corrected. The imprint cytology was a simple and effective method to diagnose the defect of limbal stem cells.