Eye Care Blog

Choice of Anaesthetic

At one time almost all intraocular surgery was performed under a local anaesthetic. For two reasons local anaesthesia is used much less commonly today. First, the whole science of general anaesthesia has greatly advanced and the likelihood of coughing has been considerably reduced. Second, methods of repairing the cataract wound are now better than they used to be. Coughing and sneezing after the operation consequently constitute less of a threat than formerly.

The decision about which type of anaesthetic is to be used is dependent largely on the patient’s personal choice provided that his overall condition does not contraindicate a general anaesthetic.

In the case of children or anxious patients a general anaesthetic is to be preferred, but in insulin-dependent diabetics a local anaesthetic may be advised so that the diabetic control is not upset. Patients with severe chest problems, heart conditions, or greatly raised blood pressure are usually better suited to local anaesthesia.

Local anaesthetic

About an hour before the operation is due to take place the patient is usually given a mild sedative, such as diazepam (Valium), which allays the anxiety that is almost inevitable at such a time. Drops of local anaesthetic and other drops to dilate the pupil are then instilled into the eye to make the operation easier to perform.

After the patient enters the operating theatre the skin around the eye and forehead is cleaned with an antiseptic solution. A number of injections are given around the eye. These have two functions: first, to deaden the area and, second, to prevent eye movements and to stop muscles around the eye from ’squeezing’. The injections are uncomfortable but not painful. One of them, given through the lower or upper lid into the tissue behind the eye, has the additional effect of making the vision in that eye very poor indeed for about an hour. The patient therefore will not be able to see details of the operation and will not be disturbed by the sight of instruments.

Although the area around the eye is completely numb, the forehead and cheek are not. The surgeon’s hands may be felt resting on the face or moving about around the area which is undergoing the operation. This has given rise to such statements as ‘They took my eye out and laid it on my cheek while they took the cataract out.’ Of course no such thing is done! It is simply that the eye itself and the surrounding tissue is completely without feeling during the operation.

After these preparatory steps have been taken all areas apart from the eye itself are covered with sterile drapes and the operation proceeds.

General anaesthetic

As with a local anaesthetic, a mild sedative may be given pre-operatively, but in this case it will be given by injection. The reason for this is that no one undergoing general anaesthesia for any reason may take anything by mouth for at least four hours before the operation because of the danger of vomiting. Vomiting while unconscious or semi-conscious is extremely dangerous.

In addition to the sedative, atropine is also given in the premedication to dry up any secretions in the mouth and throat, as these could cause problems later by making the patient cough and strain. By the time the patient reaches the operating theatre he or she is usually calm, warm, and comfortable, but has a very dry mouth.

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