Anesthesia for Eye Surgery
Ocular surgery may be performed under topical, local or general anesthesia. Local anaesthesia is more preferred because it is economical, easy to perform and the risk involved is less. Local anaesthesia has a rapid onset of action and provides a dilated pupil with low intraocular pressure.
Susruta Samhita has evidences of use of anaesthesia for ocular surgeries. Inhalational anaesthesia was used for this purpose. Egyptian surgeons used carotid compression to produce transient ischemia during eye surgery to reduce the perception of pain. In 1884, Karl Koller used cocaine for ocular surgery. The same year, Herman Knapp used cocaine for retrobulbar block. In 1914, van Lint achieved orbicularis akinesia by local injection
Topical (Surface) anaesthesia:
Surface anaesthesia is given by instillation of 2.5 ml xylocaine. One drop of xylocaine instilled four times after every 4 minutes will produce conjunctival and corneal anaesthesia. Paracaine, tetracaine, bupivacaine, lidocaine etc. may also be used in place of xylocaine. Cataract surgery by phacoemulsification is frequently performed under surface anaesthesia. Facial nerve, which supplies the orbicularis oculi muscle, is blocked in addition for intraocular surgeries. Topical anaesthesia is known to cause endothelial and epithelial toxicity, allergy and surface keratopathy.
There are four types of facial block : van Lint's block, Atkinson block, O' Brien block and Nadbath block.
van Lint's block : In van Lint's block, the peripheral branches of facial nerve are blocked. This technique causes akinesia of orbicularis oculi muscle without associated facial paralysis.
O' Brien's block : It is also known as facial nerve trunk block. The block is done at the level of the neck of the mandible near the condyloid process.
Atkinson's block : The superior branch of the facial nerve is blocked by injecting the anaesthetic solution at the inferior margin of zygomatic bone.
Nadbath block : In Nadbath block, the facial nerve is blocked at the stylomastoid foramen. The patient is likely to experience pain.
Retro bulbar block
This technique was first practiced by Herman Knapp in 1884. Here, 2% xylocaine is introduced into the muscle cone behind the eyeball. The injection is usually given through the inferior fornix of the skin of the outer part of the lower lid when the eye is in primary gaze.
Per bulbar block
This technique was first applied by Davis. In peribulbar block, 6 ml of local anaesthetic is injected to the peripheral spaces of the orbit. The anaesthetic diffuses into the muscle cone and eyelids, causing global and orbicularis akinesia and anaesthesia. After injection, orbital compression is applied for around 15 minutes.
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Anesthesiology Case Reports