Retrobulbar blockade of somatic, motor, and visual nerves by local anesthetics

Somatosensory, motor, and visual sensory blockade were investigated after retrobulbar injection of 3 mL 2% lidocaine, prilocaine, or mepivacaine plus hyaluronidase (15 U/mL) and naphazoline nitrate (1:20,000) in 90 cataract patients (n = 30 per group). Before injection as well as 20 and 90 minutes after injection, and then every 30 minutes, the quality of the retrobulbar blockade was evaluated in terms of the following factors until full recovery of function: (1) corneal sensitivity at the three extraincisional quadrants as determined with an esthesiometer; (2) horizontal and vertical motility, and elevation of the lid; (3) visual acuity on an arbitrary score scale ranging from 0 (no light perception) to 6 (visual acuity > 0.05); and (4) the time required for recovery from retrobulbar anesthesia. The data were analyzed by one- (anesthetic) and two-factor (anesthetic and time) analysis of variance. Full somatic recovery of corneal sensitivity occurred within 247 +/- 10.2 minutes after lidocaine, within 221 +/- 9.2 minutes after prilocaine, and within 280 +/- 8.5 minutes after mepivacaine (F = 10.1; P < .0001). Full motor recovery (all muscles) occurred within 290 +/- 5.8 minutes after lidocaine, within 258 +/- 5.7 minutes after prilocaine, and within 295 +/- 4.8 minutes after mepivacaine (F = 13.3, P < .0001). On the average, visual acuity decreased most after mepivacaine and least after lidocaine administration, although the differences between the three anesthetics in this regard were not significant. One patient temporarily lost vision after mepivacaine administration. Overall, the somatosensory and motor blockade were most pronounced after mepivacaine.