What are the potential complications of retrobulbar anesthesia? Are
there any other blocks that are satis-factory with less morbidity?
The onset time of retrobulbar blockade is 5–10
minutes. Retrobulbar blockade has a low failure rate of less than 1% in skilled
hands. However, retrobulbar anesthesia is asso-ciated with a number of
complications. The recognized complications of retrobulbar blockade are:
· Central retinal artery occlusion
· Retrobulbar hemorrhage
· Subdural or subarachnoid injection
· Intraneuronal injection
· Globe puncture
· Oculocardiac reflex
Peribulbar block is a good alternative to
retrobulbar block and is associated with fewer complications. To perform a
retrobulbar blockade, local anesthetic is injected into the eye’s muscle cone.
Peribulbar blockade is per-formed by injecting local anesthetic around the eye.
The failure rate of peribulbar block is as high
as 10%, and the onset time is 10–12 minutes, which is slower than that of
retrobulbar block. An alternative to the retrobulbar and peribulbar block is
the more recently popularized sub-Tenon block. The sub-Tenon block is performed
somewhat similarly to a retrobulbar block. In the sub-Tenon block a
blunt-tipped cannula is inserted between the fused conjunctiva and anterior
Tenon capsule. It is advanced to midway between the insertion of the medial and
inferior rectus muscles into a thin channel to the posterior sub-Tenon space.
Success rates are reported as high as 98.8%.