Indiana State University researchers Thomas Tsai and Dr Kathleen Dannelly have published a paper 'How dangerous is noncompliance with multipurpose solutions?' in Contact Lens Spectrum (January 2000). The authors claim that Pseudomonas aeruginosa has emerged as a 'significant threat to contact lens wearers, especially extended-wear lens wearers'. They say that it has been observed to initiate an infection of the cornea in a matter of hours and can quickly lead to vision impairment and blindness. Two strains isolated from patients' eyes were tested against five solutions: Alcon's Opti-Free Express Enhanced Disinfection Formula, Opti-Free Solution, Opti-Free Express Multi-Purpose Solution, Bausch & Lomb's ReNu MultiPlus Solution and Allergan's Complete Brand Multi-Purpose Solution. The research concluded that Opti-Free Enhanced solution was 'by far the best disinfectant'. On contact 'it reduced the number of intracellular organisms by four orders of magnitude, and reduced the extracellular by five orders of magnitute within four hours of incubation'. An Alcon spokesman said: 'Practitioners should look beyond manufacturers' claims and CE-mark approvals when choosing disinfection systems.' However, Gary Orsborne, the director of professional marketing for Bausch & Lomb (Europe) said: 'We have evidence from the Institute Pasteur in Paris that ReNu MultiPlus and ReNu Multi-Purpose deliver the highest level of disinfection efficacy of these products.' An Allergan spokesman said: 'This study confirmed our solution exceeds minimum regimen disinfection requirements with these pathogenic strains. During a four-hour soak period Complete brand killed at least 99.9 per cent of test bacteria.' He added that the paper reinforced the need for contact lens wearers to follow labelling instructions.