WAMCO Inc., a distributor of lighted components for aerospace applications, will be a distributor for Microsemi Corp.'s new line of Aviation White high-brightness white light-emitting diodes (LEDs) into that market. Microsemi makes discrete semiconductors and power management integrated circuits.   . . .   The US Food and Drug Aministration has given LaserSight Inc. approval to increase the laser pulse repetition rate of its LaserScan LSX precision microspot scanning system from 200 Hz to 300 Hz for the LASIK treatment of myopia and myopic astigmatism.