Though laser myringotomies maintain patency slightly longer than cold-knife myringotomies (two to three weeks for laser and two to three days for cold knife without tube insertion), they have not proven to be more effective in the management of effusion. One randomized controlled study found that laser myringotomies are safe but less effective than ventilation tube in the treatment of chronic OME. Multiple occurrences in children, a strong history of allergies in children, the presence of thick mucoid effusions, and history of tympanostomy tube insertion in adults, make it likely that laser tympanostomy will be ineffective.