Both long posterior ciliary arteries were occluded or the three extraocular muscles were tenotomized to produce anterior segment ischemia in rabbits, and the aqueous levels of vascular endothelial growth factor (VEGF) were measured. The occlusion of both long posterior ciliary arteries led to clinical and histological anterior segment ischemia in varying degrees. The aqueous VEGF levels increased significantly compared with controls on all days examined (Mann-Whitney U test: day 1, P = 0.0039; day 4, P = 0.0065; day 7, P = 0.0039; day 14, P = 0.0104), while the levels at days 7 and 14 decreased significantly compared with those at day 4 (Wilcoxon signed-rank test; day 4 to day 7 and day 4 to day 14, P = 0.0464). In contrast, tenotomy of the three extraocular muscles resulted in no histological changes. The VEGF levels increased significantly compared with controls at day 1 and day 4 after surgery (Mann-Whitney U test: day 1 and day 4, P = 0.0104), while the levels at day 14 decreased significantly compared with those at day 1 (Wilcoxon signed-rank test, P = 0.0499). Aqueous VEGF levels represent the severity of anterior segment ischemia and could be used as an indicator for the extent of ischemia. (C) 1998 Japanese Ophthalmological Society.