A laser is really nothing more than highly concentrated light energy. Light energy is absorbed by colored toenail polish, particularly dark colored toenail polish.
In order to treat the toenail fungus, you must remove the toenail polish before laser fungus treatment. If you didn't, the laser would vaporize the nail polish. This would generate an enormous amount of heat which would potentially damage the nail plate or even the nail bed underneath the toenail.
Dr. Christopher Segler is Board-Certified, American Board of Podiatric Medicine. He performs all laser treatments himself and does not utilize non-physician staff to perform laser fungal treatments. If you have a question about laser treatment of toenail fungus, you can call the doctor directly at 415-308-0833.