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Editor,—It seems a surprising omission from the Waldocks' recent commentary1 on the future of microsurgical instrumentation not to have mentioned contamination with specific reference to transmissible spongiform encephalopathies (TSE).
It is known that prion protein is not reliably destroyed by most disinfection or sterilisation procedures, including autoclaving at a temperature as high as 138°C for an hour.2 Although more effective methods, such as exposure to combinations of alkali and heat, are being developed3 they may require instruments to be particularly durable. Also fine, and particularly, toothed instruments require thorough cleaning before sterilisation by current procedures, to avoid retention of tissue.
Although there is no clear evidence of the transmission of TSE from one patient to another by ophthalmic surgery other than through corneal transplantation,4 the only extant Department of Health guidelines state that any instruments used on patients with Creutzfeldt-Jakob (CJD) or suspected of this condition must be destroyed. Patients with classic sporadic CJD are predominantly in their 60s and may come into contact with ophthalmologists because of cataract, glaucoma, and macular degeneration or because of visual symptoms caused by their condition.5
The number of individuals in the UK who are incubating variant CJD (vCJD), believed to be the human form of bovine spongiform encephalopathy (BSE), is unknown. Prion protein has been shown to be present in the tonsils and appendices of its victims; the possibility of it being present in the eye, and particularly in the retina and optic nerve of apparently healthy individuals, must unfortunately be entertained. The Department of Health has identified neurosurgery and ophthalmology as areas of particular risk, though arguably many forms of routine surgery could, in theory, pass on prions from one patient to another via contamination of instruments.
The only certain way to avoid the as yet unquantifiable risks of ophthalmic (or any set) surgical instruments as vectors of transmissible disease is for them to be disposable. Even then, the temptation to reuse disposable instruments for cost containment will be present. The Medical Devices Agency has already issued guidelines on devices that touch the eye, in particular contact lenses, though the full implementation of these recommendations is not possible without the eye services grinding to a halt. Nevertheless, there are situations when disposable instrumentation could be implemented—for example, eye banking, without compromising standards or indeed increasing costs, by saving on tracing and autoclaving.
We agree that surgeons, engineers, and manufacturers should engage in an active and productive debate on instrumentation for the 21st century, but this should include further initiatives to utilise new materials to facilitate disposable instruments. This dialogue may also bring about a rethink of the number of instruments on trays, the majority of which may be autoclaved time and again without being used.
Editor,—I thank Tullo and Taylor for their interest in our commentary and for highlighting a very important issue regarding the future of microsurgical instrumentation. Instrument manufacturers are aware of the implications of contamination, in particular from transmissible spongiform encephalopathies. We agree that there is a need for everyone associated with “high risk of transmission” surgery, such as ophthalmology, to rethink the strategies towards avoiding the risks of contamination. This needs to include a review of cleaning and sterilisation procedures as well as surgical instrument design.
As far as engineers and manufacturers of ophthalmic surgical instruments are concerned, there needs to be a complete reconsideration of instrument design. This includes a review of the materials being utilised, taking into account the need for durability to rigorous sterilisation procedures as well as cost. The assembly of the instruments must enable easy and thorough cleaning, while an evaluation of the methods by which manufacturing costs can be kept to a minimum may enable the production of affordable disposable instruments. Despite such criteria, it is important to maintain the high standards of quality which are required from instruments used in this field of surgery. This poses an interesting challenge and one which we agree requires an active and productive discussion from surgeons, eyebank technicians, engineers, and manufacturers,
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