The Federal Trade Commission has started an administrative enforcement proceeding against Summit Technology Inc. in Waltham, Mass., and Visx Inc. in Santa Clara, Calif. The proceeding is related to a complaint that accuses the firms of improperly sharing fees charged to doctors who use equipment made by either company. Visx and Summit make the only two FDA-approved laser systems used in a medical procedure known as photorefractive keratectomy, which corrects nearsightedness by reshaping the cornea. Each time a system is used, the doctor is billed $250. Several years ago, the two firms allegedly set up a third company, Pillar Point Partners, to split the usage fees. The commission is asking that Pillar Point Partners be disbanded. A Federal Trade Commission law judge scheduled a hearing for April 16. The judge has the authority to stop any practices found to be illegal. A source at Summit confirmed the commission's proceeding and said the company planned to defend itself against the charges.