Sir,
We thank Professor Dr J Draeger for his interest in our paper.
He agrees that single-use devices are ‘perfect, safe and reliable,’ but goes on to claim that ultraviolet (UV) irradiation of the applanation body surface is ‘equally reliable, simple and cheap.’ Our inquiries reveal that re-sterilization or decontamination by UV irradiation is considered neither safe nor effective, at least in this country. Its routine use does not appear to be accepted universally.
The references1,2,3,4 quoted by Professor Draeger report effective decontamination of devices when exposed to various viruses, but no evidence is provided that UV irradiation was effective when they were exposed to the agent responsible for vCJD. In the document5 produced by two expert advisory committees to the Government, UV irradiation is listed under Table B.2 as one of the ‘Chemicals & processes INEFFECTIVE against TSE agents’ (authors’ emphasis).
In a more recent directive6 than the one quoted in our article, the Medical Devices Directorate repeats the advice that ‘the devices that touch the surface of the eye should be restricted to single patient use.’ Unless our sterilization and disinfecting processes are proven totally safe and effective against all known pathogens including the agent responsible for vCJD, ophthalmologists will be turning to disposable instruments where available.
Professor Draeger claims that the use of disposable devices seems to be a more expensive method of avoiding contamination, but at just over 70 pence (UK) each prism and 33 cents (USA) for each silicone shield, the cost of the devices represents a very small addition to the costs of service provision.
References
Draeger J, Hinzpeter Th, Mai K . Untersuchungen zur Tonometersterilisation. Doc Ophthal 1969; 26: 648–663
Draeger J . Einfache Möglichkeit zur Tonometersterilisation. Klin Mbl Augenheilk 1970; 157: 70–74
Schmitz H, Draeger J . Inaktivierung von HTLV-III/LAV durch UV-Bestrahlung und chemische Desinfektion. Klin Mbl Augenheilk 1985; 189: 154–157
Schmitz H, Draeger J, Emmerich P . Inaktivierung von Herpes-simplex-Virus Typ I (HSV-I) und Adenovirus (Typ II) durch ultraviolette Bestrahlung. Klim Mbl Augenheilk 1990; 196: 225–227
Advisory Committee on Dangerous Pathogens, Spongiform Encepalopathy Advisory Committee. Transmissible spongiform encephalopathy agents: safe working and the prevention of infection The Stationery Office: London 1998 ISBN 0113221665 Annex B; Table B.2: 45
Medical Devices Directorate. Sterilization, Disinfection and Cleaning of Medical Equipment: guidance on decontamination from the Microbiology Advisory Committee to Department of Health 2000 ISBN 1858395186 Part 2 Protocols. Section 2.38
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Desai, S., Sivakumar, S. & Fryers, P. Evaluation of a disposable prism for applanation tonometry. Eye 16, 675 (2002). https://doi.org/10.1038/sj.eye.6700129
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DOI: https://doi.org/10.1038/sj.eye.6700129