Although all types of anaesthesia are compatible with bimanual phaco, local anaesthesia remains the most reasonable alternative as compared to locoregional or general anaesthesia in microincision cataract surgery. This has been made possible by the developments inherent in bimanual phaco, including microincision surgery at constant intraocular pressure and by the advent of soft and injectable intraocular lenses capable of being introduced through incisions of less than 1.5 mm.
Local anaesthesia in ophthalmology has been known since 1884 when Knapp used a 5% cocaine solution in cataract surgery. However, this technique was later abandoned due to its high degree of toxicity in respect of the corneal epithelium, and replaced first by retrobulbar and later by peribulbar anaesthesia. Only in 1991 did Richard Fichman reintroduce local anaesthesia using tetracaine in cataract surgery by phacoemulsification. In 1995, James Gills made it possible systematically to use local anaesthesia by means of intracameral injection of a 1% lidocaine solution without preservatives.
The sensitive nerve system of the anterior segment of the eye consists of the short ciliary nerves, arising from the ciliary ganglion and entering into the sclerotic coat around the optical nerve. Their ends travel through the suprachoroidal space from back to front to constitute the ciliary plexus on the external face of the ciliary body. From this plexus arise internal rami dedicated to the ciliary body and the iris, and external rami dedicated to the cornea. The external rami pierce the sclerotic coat 3 mm behind the limbus and subdivide into a rich pericorneal network. This arrangement accounts for the quality of the analgesic effect on the cornea under local anaesthesia and the persistence of iridociliary sensitivity. This type of anaesthesia is therefore perfectly appropriate for clear cornea microincision surgery.
Present day local anaesthesia protocols comprise four modes that can be used separately or in combination: Instillation of anaesthetic collyria, use of anaesthetic gel, intracameral injection of a local anaesthetic and use of a viscoanaesthetic product (viscoelastic anaesthetic).
The most frequently instilled collyria are: Oxybuprocaine as it is innocuous; tetracaine at 0.5 or 1%, whose duration of action is of 20 minutes; and bupivacaine, with a longer duration of action. No more than three or four preoperative instillations should be made in order not to alter the corneal epithelium and to preserve its transparency. The reduced transcorneal penetration of anaesthetic collyria generates low intracamerular concentrations, which explains the persistence of iridociliary sensitivity. Patients retain tactile, pressure and burn sensitivity.
Anaesthetic gels based on 2% lidocaine solutions are relatively popular because they prevent repetitive collyrium instillation and their persistence on the eye surface provides greater anaesthetic comfort. However, cases of infectious endophtalmitis have been reported with this procedure, explained by a likely screening effect of the gel as regards the iodated polyvidone whose antiseptic capacity is reduced. Therefore the importance of carrying out the antiseptic stage prior to application of the gel in the inferior conjunctival fornix to prevent septic complications should be kept in mind.
A 10 second intracameral injection of 0.3 ml 1% lidocaine without preservative followed by an exchange with the viscoelastic product advantageously completes local anaesthesia of the eye surface. This approach is justified by the absence of anaesthesia of the ciliary body as discussed above when anaesthetic collyria are instilled. The patient’s comfort is improved and the intraocular pressure sensation is less frequently reported. Without preservatives, lidocaine has no toxic effects on the corneal endothelium. Intracamerular lidocaine should not be used in the presence of lesions of the posterior capsule or of the zonule in order not to compromise the integrity of the retinal ganglion cells and the optical nerve as a result of the toxic effect of lidocaine.
More recently, the association of an anaesthetic (1% lidocaine without preservatives) with a viscoelastic product (sodium hyaluronate) in one and the same pre-filled sterile syringe has simplified the intracamerular anaesthesia procedure. For the time being, no eye structure toxicity has been reported, and there is no modification to the behaviour of the viscous product.
The main arguments in favour of local anaesthesia as compared to locoregional anaesthesia are the elimination of iatrogenic risks connected with periocular injections, less onerous anaesthesia protocols for outpatient surgery, increased patient comfort with more active preoperative participation and immediate post-operative visual recovery. Ocular akinesia becomes optional as two intraocular instruments introduced through two microincisions can easily stabilise the eyeball during the bimanual phaco intervention. Active perioperative patient cooperation is obtained by maintaining reassuring verbal contact throughout the procedure. In the absence of amaurosis, the light of the surgical microscope can be set as necessary to prevent eye movements. Analgesia lasts for about twenty minutes, appropriately covering the duration of a bimanual phaco intervention.
How to manage perioperative problems under local anaesthesia ?
In the event of eye pain, multiplying the instances of anaesthetic collyrium instillation most frequently has no result other than causing epithelial oedema that may negatively affect the proper course of the intervention. It is preferable to reinject lidocaine at 1% intracamerular without preservatives to improve patient comfort during the procedure.
In the event of a failure at the capsulorhexis stage, pursuing the intervention with the bimanual phaco technique is generally contraindicated. At that point it would be better to change operative techniques and perform periocular anaesthesia after having emptied the anterior chamber of viscoelastic product.
In the event of a simple capsular rupture or of a rupture associated with an egress of vitreous substance, it is possible to continue under local anaesthesia to perform bimanual anterior vitrectomy reshaping the anterior segment with viscoelastic product. No intracamerular lidocaine reinjections should be performed with this type of complication.
In the event of nuclear fragments falling into the vitreous body, anterior segment cleaning is normally completed under local anaesthesia. This serious complication should be treated secondarily under locoregional or general anaesthesia by a practitioner specialising in posterior segment surgery.
