[The effect of preventing anterior segment ischemia by preservation of anterior ciliary vessels in rabbit].

Objective: To investigate the effect of preserving anterior ciliary vessels (ACVs) on the prevention of anterior segment ischemia syndrome (ASI) during the surgery of extraocular muscles.

Methods: Thirty-two adult New Zealand white rabbits were randomly divided into four groups. ACVs of the right eyes were preserved among all of the rabbits, and were cut off in all of the left eyes. Group A: internal and external recti were cut off in two eyes; Group B: superior and inferior recti were cut off in two eyes; Group C: internal, external and superior or inferior recti were cut off in two eyes; Group D: all of the recti were cut off in two eyes. All rabbits were observed under slit microscope. The intraocular pressure (IOP), the total protein and lactic acid in the aqueous humor were recorded preoperatively and postoperatively. Eyes were enucleated at the forth week postoperatively to obtain the iris and the ciliary body for histopathologic study and electron microscopy.

Results: No signs of ASI were observed in the right eyes of all four groups under the slit lamp and under the light and election microscopes. The IOP and levels of ingredients of aqueous humor (total protein and lactic acid) showed no difference between preoperative and postoperative interval. No obvious ASI was observed in the left eyes of group A. Mild reactions of ASI were observed in the left eyes of group B. Moderate to severe reactions of ASI were observed in the left eyes in group C and group D. The IOP reduced from (17.21 +/- 3.76) mm Hg (1 mm Hg = 0.133 kPa) preoperatively to (14.48 +/- 3.36) mm Hg postoperatively in group C (P < 0.05); and from (16.68 +/- 2.33) mm Hg reduced to(3.17 +/- 0.92) mm Hg in group D. (P < 0.05). The level of total protein and lactic acid in the aqueous humor increased from (505.3 +/- 5.0) mg/L and (7.54 +/- 0.47) g/L preoperatively to (811.9 +/- 44.4) mg/L and (11.00 +/- 3.59) g/L postoperatively in group C, respectively (P < 0.05). In group D, the level of total protein and lactic acid in the aqueous humor increased from (504.6 +/- 4.1) mg/L and (7.17 +/- 1.44) g/L preoperatively to (1025. 8 +/- 78.3) mg/L, (8.23 +/- 1.68) g/L postoperatively, respectively (P < 0.05). There were various histopathological changes under the light and electron microscope in groups C and D. While no obvious ischemic changes were observed in group A.

Conclusion: Two vertical muscles cut off at one eye simultaneously would produce mild reactions of ischemia, while three or more muscles cut off simultaneously could obstruct blood flow in eyes and induce ASI. Preservation of the ACVs could avoid the occurrence of ASI.