Wound healing assay - (Oct/22/2015 )

I have a question. For wound healing assay of cancer cell culture, once essential oil is used for treatment and observed under the microscope, the scratch formed cannot be seen and measured due to numerous oil droplets. Can anyone who has experienced the same situation or has knowledge in this area explain how to avoid the droplets from interfering with photo capturing and capture the scratch? Thank you in advance.

Could you wash the oil off and then replace?