Ocular Anasthesia (Facial 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
Facial block
For intraocular surgery it's necessary to dam the facial which supplies the orbicularis oculi muscle, in order that patient cannot squeeze the eyelids.
Orbicularisakinesia are often achieved by blocking the facial at its terminal branches (van Lint block), superior branches (Atkinson block) or proximal trunk (O’Brien or Nadbath block).
1. Blocking the peripheral branches of facial nerve:
this system blocks the terminal branches of the facial , producing localized akinesia of the orbicularis oculi muscle without associated facial paralysis.
In this technique, 2.5 ml of anaesthetic solution is injected in deeper tissues just above the eyebrow and slightly below the inferior orbital margin, through some extent about 2 cm behind the lateral orbital margin, level with outer canthus.
2. facial trunk block:
In it facial is blocked near the condylar process.
The condyle is found 1cm anterior to thetragus.
it's easily palpated if the patient is asked to open and shut the mouth with the operator’s index located across the neck of the mandible.
At now the needle is inserted until contact is formed with the periosteum then 4 to six ml of local anesthetic is injected while the needle is withdrawn.
This technique is related to pain at the injection site and unwanted facial paralysis.
3. Nadbath block:
during this technique, the facial is blocked because it leaves the skull through the stylomastoid foramen. This block is additionally painful.
4. Atkinson’s block:
In it superior branches of the facial are blocked by injecting anesthetic solution at the inferior margin of the cheekbone .
Retrobulbarblock
Peribulbarblock
Local Anasthesia
Ocular Anasthesia
Tags:
ANASTHESIA