Notwithstanding the provisions of § 46.2-1052, a motor vehicle operated by or regularly used to transport any person with a medical condition which renders him susceptible to harm or injury from exposure to sunlight or bright artificial light may be equipped, on its windshield and any or all of its windows, with sun-shading or tinting films or applications which reduce the transmission of light into the vehicle to levels not less than 35 percent. Such sun-shading or tinting film when applied to the windshield of a motor vehicle shall not cause the total light transmittance to be reduced to any level less than 70 percent except for the upper five inches of such windshield or the AS-1 line, whichever is closer to the top of the windshield. Vehicles equipped with such sun-shading or tinting films shall not be operated on any highway unless, while being so operated, the driver or an occupant of the vehicle has in his possession a written authorization issued by the Commissioner of the Department of Motor Vehicles authorizing such operation. The Commissioner shall issue such written authorization only upon receipt of a signed statement from a licensed physician or licensed optometrist (i) identifying with reasonable specificity the person seeking the written authorization and (ii) stating that, in the physician’s or optometrist’s professional opinion, the equipping of a vehicle with sun-shading or tinting films or applications is necessary to safeguard the health of the person seeking the written authorization. Written authorizations issued by the Commissioner under this section shall be valid so long as the condition requiring the use of sun-shading or tinting films or applications persists or until the vehicle is sold, whichever first occurs. Such written authorizations shall permit the approval of any such vehicle upon its safety inspection as required by this chapter if such vehicle otherwise qualifies for inspection approval. In the discretion of the Commissioner, one or more written authorizations may be issued to an individual or a family. The Division of Purchases and Supply, pursuant to § 2.2-1112, shall determine the proper standards for equipment or devices used to measure light transmittance through windows of motor vehicles. Law-enforcement officers shall use only such equipment or devices to measure light transmittance through windows that meet the standards established by the Division. Such measurements made by law-enforcement officers shall be given a tolerance of minus seven percentage points. For any summons issued for a violation of this section, the court may, in its discretion, dismiss the summons, where proof of compliance with this section is provided to the court on or before the court date.