Effects of sub-Tenon's anaesthesia on ocular hemodynamics.

OBJECTIVE: To research the effects of sub-Tenon's anaesthesia (STA) on ocular hemodynamics in patients with cataract using colour Doppler imaging (CDI). DESIGN: Prospective clinical study. PARTICIPANTS: Thirty-four eyes of 34 patients with age-related cataract. METHODS: Peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) values of the ophthalmic artery (OA), central retinal artery, and central retinal vein were measured by CDI before and immediately after performing sub-Tenon block using 2 mL of 2% lidocaine with adrenaline (1:200 000). RESULTS: Both PSV and EDV values were significantly decreased after sub-Tenon injection in all the studied vessels of the patients. However, no important changes were observed in the RI values of the vessels. CONCLUSIONS: STA markedly reduced ocular blood flow. The reduction may be more acceptable compared with other retrobulbar block methods. Sub-Tenon block should be performed carefully to senile patients with cataract with vascular occlusive disorder.

[Physiological mechanism for the regulation of ocular circulation].

Ocular circulation is regulated to maintain the homeostasis of retinal function in response to physiological stimulus. It is important to understand the mechanism of the regulation of ocular circulation under physiological conditions because the impairment of ocular circulation should cause severe retinal disorders. We previously investigated the physiological mechanism of ocular circulation in response to hypoxia, hypercapnia, and acute increased systemic blood pressure. In addition, it was reported that transpupillary thermotherapy might change ocular blood flow in patients with age-related macular degeneration. However, it still remains unclear whether the increased ocular tissue temperature may be associated with alteration of the ocular blood flow. Therefore, we examined the effect of ocular warming on retinal blood flow (RBF) and subfoveal choroidal blood flow (CBF) in humans. Ocular warming was induced in 10 healthy volunteers using an ocular warming lamp for 10 minutes. The RBF in the retinal artery and vein and the CBF in the foveal region were examined with a retinal laser Doppler velocimetry system and a laser Doppler flowmeter, respectively. Ocular warming increased RBF in the retinal artery and vein but decreased CBF in the foveal region. The CBF in the foveal region may contribute to maintaining a constant retinal temperature in response to ocular warming.

Colour Doppler imaging before and after retrobulbar anaesthesia in patients undergoing cataract surgery.

PURPOSE: To investigate the effect of retrobulbar anaesthesia on retrobulbar haemodynamics, colour Doppler imaging was performed. Furthermore, the additive effect of epinephrine was examined. METHOD: Forty-one patients (age 72.7+/-8.9; 22 f, 19 m) undergoing planned cataract surgery were included in a prospective study. Colour Doppler imaging was performed before and directly after retrobulbar anaesthesia and after cataract surgery to measure the peak systolic velocity (PSV) and end-diastolic velocity (EDV) in the ophthalmic artery, central retinal artery and central retinal vein. In 18 patients lidocaine 2% without additives (2 ml, retrobulbar transconjunctival injection) and in 23 patients lidocaine 2% with epinephrine 1:200,000 was used. RESULTS: After retrobulbar anaesthesia both groups had a significant reduction of the PSV and of the EDV. After surgery flow velocities increased again. The addition of epinephrine resulted in a significantly greater reduction and slower recovery of flow velocities. CONCLUSION: Retrobulbar anaesthesia induces a marked reduction of velocity in the retrobulbar vessels. The supplement epinephrine increases this effect, and recovery is much slower. Thus, particularly in patients with already disturbed ocular haemodynamics epinephrine should not be used in order to avoid irreversible functional damage.