Caritas Medical Centre is investigating why surgical knives used in cataract operations were not thoroughly sterilised. The 13 patients on whom the knives were used have no infections.

Instruments used in cataract operations are thoroughly cleansed and heat dried before they are packed individually for chemical sterilisation. But a recent review found the last step in the sterilisation process for the 13 knives had not been properly completed.

The four men and nine women, aged 57 to 80, who received the operation from November 7 to 16 will be closely monitored.

The centre is reviewing its sterilisation procedures and staff have been reminded to boost vigilance.