11.7 Local anaesthetics
Oxybuprocaine hydrochloride 0.4% (benoxinate hydrochloride, single use eye drops) is the recommended local anaesthetic for ophthalmic use. It causes less initial irritation than tetracaine and has a very rapid onset of action (about 30 seconds).
Lidocaine 4% and fluorescein 0.25% (single use eye drops) is used in tonometry. Avoid in preterm neonates.
Proxymetacaine 0.5% (single dose eye drops) causes less initial stinging and is useful for children. Use with care in preterm neonates.
Proxymetacaine 0.5% and fluoresceine 0.25% (single dose eye drops). Avoid in preterm neonates. Used as for lidocaine/fluorescein.
Tetracaine 0.5% and 1% (single use eye drops) has a longer duration of action than oxybuprocaine but is more likely to cause stinging, which may be extremely painful.
Cocaine 4% eye drops [unlicensed product] has local anaesthetic and vasoconstrictor actions. It is used in the diagnosis of Horner's syndrome and as a nasal vasoconstrictor prior to DCR surgery.
PRESCRIBING POINTS FOR LOCAL ANAESTHETICS
- Local anaesthetic eye drops should not be used for the symptomatic control of pain. Not recommended for welders flash, other than for diagnostic purposes.
- Local anaesthetics should never be used for the management of ocular symptoms.
- The use of local anaesthetic eye drops is essential when removing foreign bodies from the eye.
- Patients should be warned that the eye drops might sting.
- One drop instilled and repeated once after 1 minute will provide effective ocular surface anaesthesia for 10-20 minutes.