Effects of irrigation fluid temperature on choroidal circulation during vitrectomy.

PURPOSE: To investigate the effects of irrigation temperature on choroidal circulation during vitrectomy. METHODS: After anesthetized albino rabbits underwent closed vitrectomy, choroidal blood flow was monitored while the vitreous cavity was irrigated with solutions (BSS plus) of various temperatures (6-42 degrees C). Irrigation pressure was maintained at 15 mmHg. A non-contact Doppler laser flowmeter was used to measure choroidal blood flow. Temperature change at the retina and mid-vitreous was also measured during irrigation. RESULTS: Choroidal blood flow showed a downward peak when perfused at 34 degrees C. As irrigation temperatures deviated above or below 34 degrees C, the blood flow increased. However, when irrigation temperature was below 16 degrees C, the blood flow decreased as the temperature declined. The temperature at the retina was maintained at a relatively constant level when irrigation was between 30 degrees C and 40 degrees C. CONCLUSION: The choroid acts as a thermostat to minimize intraocular temperature fluctuations by changing its blood flow.