What is the best method of sterilising the lenses of opthalmic microscope lenses? Can it be done with glutaraldehyde? What is the immersion time required? Are lenses manufactured by all companies compatible with glutaraldehyde?

Dear Dr Kulkarni,

Because microscopes are not waterproof, it is not possible to sterilize the distal ends by immersion in e.g. glutaraldehyde solutions. In our hospital we cover the surgical microscopes with disposable sterile microscope drapes.

Best regards,
Wim Renders
p.s. To obtain sporocidal activity the immersion time in glutaraldehyde (Cidex) is at least 10 hours. For tuberculocidal, virucidal, bactericidal, fungicidal activity at least 20 minutes immersion time is required.

Dear Dr Kulkarni,

I didn't feel so happy with my answer on your question. It sounds rather utopic and may not reflect common practice. I did an inquiry in a university hospital in Belgium. The ophtalmologists there don't want to use drapes to cover their microscopes during surgery. They just don't like it. They do the following:

• After each procedure the microscope is carefully cleaned with water and a detergent, rinsed and dried.
• Before use the microscope is sprayed with isopropanol 70°. The microscope is given time to dry. Manipulations of the microscope during surgery are done with sterile gloves.

Of course the use of drapes is the best practice. But this procedure can offer an valuable alternative.

Kind regards,
Wim Renders