Retrobulbar block
Ocular surgery may be performed under topical, local or general anaesthesia.
Local anaesthesia is more frequently employed as it entails little risk and is less dependent upon patient’s general health.
It is easy to perform, has got rapid onset of action and provides a low intraocular pressure with dilated pupil. Above all, in developing countries like India, with a large number of cataract cases, it is much more economical.Retrobulbar block was introduced by Herman Knapp in 1884.
it's administered by injecting 2 ml of anaesthetic solution (2% xylocaine with added hyaluronidase / ml and with or without adrenaline one in one lac) into the muscle cone behind the eyeball.
It's usual to offer the injection through the inferior fornix or the skin of outer a part of lower lid with the attention in primary gaze.
The needle is first directed straight backwards then slightly upwards and inwards towards the apex of the orbit, up to a depth
of 2.5 to 3 cm.
Retrobulbar block anaesthetizes the ciliary nerves, ciliary ganglion and third and sixth cranial nerves thus producing globe akinesia, anaesthesia and analgesia.
The superior oblique muscle isn't usually paralyzed as the fourth nerve is outside the muscle cone.
Complications
Retrobulbar haemorrhage
Globe perforation
Optic nerve injury
Extraocular muscle palsies
Tags:
ANASTHESIA