| Eye Anaesthesia |
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A good anaesthesia , either local or general, is essential for smoother surgery to save
sight ,and indeed, bad anaesthesia may be disastrous. |
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Local Anaesthesia (LA) |
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Most eye surgeons prefer to do cataract and other operations under local anaesthesia.
Advantages
1- It is easy to administer, and there is no need of trained anaesthetist.
2- Patient can co-operate during surgery.
3- It needs no special and costly investigations.
4- There is no major complication of GA example cardio – respiratory problems,
coughing, vomiting etc.Immediate post operative recovery is uneventful.
5- It is much less costly.
Disadvantages
1- It is difficult and sometimes hazardous for the nervous and non-co-operative
patients.
2- Head movements and straining ,may cause serious complications.
3- Cardiac shock may also occur in susceptible individual.
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General Anaesthesia (GA) |
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The agents commonly used
1- Anaesthetic agents;
- Inj lignocaine (2%) Onset of action 5-10 minutes ,duration of action 45 minutes-2
hours.
- Inj bupivacaine(0.50%- 0.75%) Onset of action 15-20 minutes , duration of action 5-8
hours
2- Adjuvents;
- Inj adrenaline(1 in 100,000) It decreases the systemic absorption of the anaesthetic
agent by local vasoconstriction.It also reduces the chance of bleeding, and prolongs the
duration of action.It is contraindicated in hypertension and heart diseases.
- Inj hyaluronidase –It enhances the diffusion of anaesthetic agents through the tissues. It
is used 75- 150 units/10 mlof anaesthetic solution. |
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Types of Local Anaesthesia |
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1- Surface Anaesthesia – This is either by instillation of 4%lignocaine or 0.5%-1%
amethocaine, twice at an interval of 5 minutes.It is most commonly required for
the removal of corneal foreign body ,syringing, tonometry or gonioscopy.
2- Infiltration (regional) anaesthesia- There is no need to say more than a few words
of encouragement and assurance , and to give a preliminary warning about the
prick of the needle which injects the anaesthetic solution. |
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Types of Infiltration Anaesthesia? |
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Infiltration anaesthesia is best achieved by a “mixture” con taining 50% of inj lignocaine
with adrenaline ( for rapid onset)+ 50% of inj bupivacaine ( for long duration of action)+
inj hyaluronidase .
Types of Infiltration Anaesthesia
1- Facial Block –It is to block the facial nerve ,or its zygomatic branch to paralyse the
orbicularis oculi muscle.The aim is to prevent closure and squeezing of eyelids during
operation.
2-Retro– bulbar block- The patient is asked to look up and opposite side.A long needle
(35mm)is introduced at the junction of middle –third and lateral- third along the inferior
orbital margin , and then directed backwards and medially, towards the apex of the
orbit.1-2 ml of anaesthetic solution is injected .Onset is indicated by mydriasis.The aim is
to block the ciliary ganglion,and to paralyse the extra ocular muscles.
3-Peribulbar block- Most surgeons have abandoned the retro bulbar block in favour of
peribulbar injections at superior and inferior parts of peripheral space of the orbit ,with a
23 or 24 gauge needle.
The superior injection is given superonasally beneath the superior orbital notch, with the
needle directed towards the orbit roof.
The inferior injection is given at the junction of middle and outer third of the lower
orbital margin.With the patient looking up ,the needle is directed towards the floor of the
orbit.
- A constant bulbar pressure is given against the closed eyelids for 10 minutes with the
help of fingers , “super pinky”or Honan balloon .This is to achieve lowering of IOP, and
reduction of orbital volume.
-It has all the effects of facial,retrobulbar and surface anaesthesia.
4-Regional blocks (at other sites)
They are different ,for different extra-ocular operations e.g.for dacryocystectomy or
Dacryocysto –rhinostomy operation, for lid tumours , for ptosis etc. |
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Author: Dr. Sanjay Dhawan
Last Updated on: 1 March, 2014 |
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