Objective To evaluate the orbital bone quantity by spiral computer tomography（CT） for orbital implant operation. Methods Fifty -two normal skull specimens with marks received spiral CT scan and their multiplanar images were obtained. The quantity （length×width） were measured on multiplanar images. Results The right orbital bone quantity at 7∶00 was the highest, average 11.91 mm×8.38 mm, and at 3∶00 was the lowest, average 2.31 mm×1.34 mm. The left orbital bone quantity at 5:00 was the highest, average 12.03 mm×8.56 mm, and at 9∶00 was the lowest, average 2.44 mm×1.29 mm. There had no significance correlation with gender at the same position in both sides. Conclusion Useful data had been obtained for the selection of the placement sites, direction, length, and diameter of orbital implants.
