The three-member panel, in cooperation with the department, shall establish and use a uniform permanent impairment rating schedule. This schedule must be based on medically or scientifically demonstrable findings as well as the systems and criteria set forth in the American Medical Association's Guides to the Evaluation of Permanent Impairment; the Snellen Charts, published by the American Medical Association Committee for Eye Injuries; and the Minnesota Department of Labor and Industry Disability Schedules. The schedule must be based upon objective findings. The schedule shall be more comprehensive than the AMA Guides to the Evaluation of Permanent Impairment and shall expand the areas already addressed and address additional areas not currently contained in the guides. On August 1, 1979, and pending the adoption, by rule, of a permanent schedule, Guides to the Evaluation of Permanent Impairment, copyright 1977, 1971, 1988, by the American Medical Association, shall be the temporary schedule and shall be used for the purposes hereof. For injuries after July 1, 1990, pending the adoption by rule of a uniform disability rating agency schedule, the Minnesota Department of Labor and Industry Disability Schedule shall be used unless that schedule does not address an injury. In such case, the Guides to the Evaluation of Permanent Impairment by the American Medical Association shall be used. Determination of permanent impairment under this schedule must be made by a physician licensed under chapter 458, a doctor of osteopathic medicine licensed under chapters 458 and 459, a chiropractic physician licensed under chapter 460, a podiatric physician licensed under chapter 461, an optometrist licensed under chapter 463, or a dentist licensed under chapter 466, as appropriate considering the nature of the injury. No other persons are authorized to render opinions regarding the existence of or the extent of permanent impairment.