Proxymetacaine is the local anaesthetic of choice for removal of corneal foreign bodies
Date First Published:
May 5, 2005
Last Updated:
July 29, 2005
Report by:
Jonel Steffen, SHO (St Mary's hospital, Paddington)
Search checked by:
Nicola Batrick, St Mary's hospital, Paddington
Three-Part Question:
In [an adult presenting for removal of a corneal foreign body] is [proxymetacaine the optimal local anaesthetic] at [achieving anaesthesia with best patient tolerability]?
Clinical Scenario:
A 24 year old woman presents to the Emergency Department with a corneal foreign body. You wonder which topical anaesthetic agent will provide adequate anaesthesia for removal of the foreign body with the least amount of stinging on instillation.
Search Strategy:
Medline 1966-04/2005 using the Dialog interface and by scanning the references of relevant papers.
Search Details:
[topical ADJ anesthesia OR topical ADJ anesthetics OR local ADJ anesthesia OR local ADJ anesthetics] AND [proxymetacaine OR propoxycaine OR proparacaine] AND LG=EN AND HUMAN=YES AND ADULT
Outcome:
Altogether 40 papers were found of which 38 were irrelevant or of insufficient quality. A further 3 papers were found by scanning the references of relevant papers, of which 1 was of insufficient quality. The four relevant papers are summarised in the table.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Topical anesthesia: Proxymethacaine vs Amethocaine for clear corneal phacoemulsification. Hamilton R, et al. 1998 UK. | 40 patients for routine corneal phacoemulsification 20 received topical 0.5% Proxymetacaine 20 received topical 1% Amethocaine |
Prospective study | Mean post-instillation pain score (scale 0-10) | Proxymetacaine 0.25, Amethocaine 2.70, (p<0.01) | Small sample size with no power calculation No details of randomisation Not blinded to investigators |
| Mean intra-operative pain score (scale 0-10) | Proxymetacaine 0.25, Amethocaine 0.25, (Not clinically significant) | ||||
| Mean pain score 2 hours after operation (scale 0-10) | Proxymetacaine 0.05, Amethocaine 0.15, (Not clinically significant) | ||||
| A comparison of Proparacaine and Tetracaine eye anesthetics. Bartfield JM, et al. 1994 USA. | 24 healthy adult volunteers 0.5% Proparacaine in one eye 0.5% Tetracaine in other eye |
Prospective, randomised, double-masked clinical trial | Mean pain score after instillation (Visual analog pain scale of 0-100mm) | Proparacaine 2mm, Tetracaine 26mm, (p<0.0002) | Power calculation showed 24 patient are adequate, but only 23 patients used for data analysis Depth of anaesthesia not evaluated |
| Duration of anaesthesia (Minutes to return of corneal blink reflex) | Proparacaine 10.7min, Tetracaine 9.4min, (p=0.0001) | ||||
| Comparison of the tolerability and efficacy of unit-dose, preservative-free topical ocular anaesthetics. Lawrenson JG, et al. 1998 UK. | 14 healthy male volunteers 2 sessions with installation of 0.4% Benoxinate, 0.5% Amethocaine, 0.5% Proxymetacaine and 0.9% Normal Saline consecutively in eyes |
Double-masked crossover trial | Mean discomfort rating after instillation (Linear 10 point arbitrary comfort scale) | Proxymetacaine 2.8, Benoxinate 6.1, Amethocaine 5.1, Normal Saline 0.9, (Proxymetacaine vs Benoxinate p<0.001, Proxymetacaine vs Amethocaine p<0.01, Benoxinate vs Amethocaine not significant) | Small sample size with no power calculation |
| Percentage of patients achieving total anaesthesia 1 minute post-instillation (Measured with Cochet-Bonnet anaesthesiometer) | Proxymetacaine 100%, Benoxinate 100%, Amethocaine 100% | ||||
| Randomised prospective masked study comparing patient comfort following the instillation of topical Proxymetacaine and Amethocaine. Shafi T, et al. 1998 UK. | 53 consecutive patients requiring tonometry at ophthalmic outpatient department 0.5% Proxymetacaine in one eye 0.5% Amethocaine in other eye |
Randomised, masked, double-blind, prospective study | Mean duration of stinging | Proxymetacaine 3.2 seconds, Amethocaine 22.1 seconds, (p<0.001) | Possible incorrect value for mean descriptive discomfort score of Amethocaine |
| Mean descriptive discomfort score (0-4) | Proxymetacaine 2.6, Amethocaine 14.2, (p=0.01) | ||||
| Mean linear analogue discomfort score (0-100mm) | Proxymetacaine 5.8, Amethocaine 35.6, (p<0.001) | ||||
| Successful tonometry as measure of adequate anaesthesia | Proxymetacaine 93%, Amethocaine 98%, (Not statistically significant with p=0.08) |
Author Commentary:
The above studies show that Proxymetacaine provides adequate corneal anaesthesia with significantly less stinging than other topical anaesthetic agents on the UK market. Using a topical anaesthetic agent that causes less pain on instillation is important, not only in minimising patient discomfort, but also to encourage further cooperation from an apprehensive patient. This may be of particular significance in the paediatric population, although children were not considered in this Best Bet.
Bottom Line:
Proxymetacaine is the topical anaesthetic of choice for the removal of corneal foreign bodies because it is significantly better tolerated by patients, with similar clinical efficacy.
References:
- Hamilton R, et al.. Topical anesthesia: Proxymethacaine vs Amethocaine for clear corneal phacoemulsification.
- Bartfield JM, et al.. A comparison of Proparacaine and Tetracaine eye anesthetics.
- Lawrenson JG, et al.. Comparison of the tolerability and efficacy of unit-dose, preservative-free topical ocular anaesthetics.
- Shafi T, et al.. Randomised prospective masked study comparing patient comfort following the instillation of topical Proxymetacaine and Amethocaine.