Cross infection risks from hand held lenses and slit lamps: an evaluation of current cleaning practices

Abstract

Abstract: : Purpose:The risk of cross infection from ophthalmological equipment is well recognised, in particular contact tonometry. We studied the potential for transmission of infection via non–contact hand held lenses (78D, 90D etc), where rigorous cleaning is not normally undertaken. In conjunction, we evaluated the effectiveness of our current practice in cleaning of slit lamps. Methods:A total of 27 hand held lenses were sampled by rolling the lenses onto a culture plate using a gloved hand before and after cleaning with a 70% isopropyl alcohol wipe. A swab moistened in normal saline was used to sample the well of each lens case. Moist swabs were also taken from the central part of the head and chin rests of ten slit lamps before and after cleaning with a solution of detergent and water prior to the start of a clinic. Further swabs were taken at the end of the clinic. Results: Sampling of the lenses showed bacterial growth in 22/27 (81%); the majority being skin flora but S. aureus was isolated from 3/22 lenses (14%). After cleaning with an alcohol wipe none of these lenses showed any significant growth. Lens case swabs showed mainly growth of skin flora in 12/27 (44%) but S. aureus was isolated from one case. Swabs from the slit lamps prior to cleaning showed growth of skin flora in 13/20 (65%) that decreased to only 3/20 after cleaning. At the end of the clinic 16/20 swabs showed bacterial growth (15 skin and 1 S. aureus). Overall, no methicillin resistant S.aureus (MRSA) or gram–negative organisms were isolated. Conclusions: Despite the low level of contamination of hand held lenses, lens cleaning decreased the bacterial load and was effective against potential pathogens. We propose that regular lens cleaning should be undertaken to minimise the potential of cross infection. A possible risk of transmission of infection from the lens case remains and methods for cleaning these cases should be considered. Our current practice of cleaning of slit lamps appears effective in reducing the bacterial load. Nevertheless, slit lamps should be cleaned between patients to prevent nosocomial transfer.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • clinical (human) or epidemiologic studies: health care delivery/economics/manpower • Staphylococcus