Minimising the risk of prion transmission by contact tonometry.

AIMS The unknown prevalence of variant Creutzfeldt-Jakob disease (vCJD) in the UK population has led to fears of horizontal transmission through routine medical procedures. The potential risk of transmission via contact tonometry was examined. METHODS The total amount of protein carried over by tonometer tips after applanation of patients was assessed. RESULTS Tonometer tips had an inherent ability to carry proteinaceous material. There was a large variability in the load carried over between individual patients. Rinsing tonometer tips in water reduced protein carryover. Wiping the tonometer tips also reduced carriage, though less dramatically. CONCLUSION There is a small theoretical risk of transmission of vCJD by contact tonometry through reuse, but this should be reduced if the prisms are washed and wiped. In the light of these findings a protocol for the management of reusable tonometer prisms is recommended.