The invention provides compounds of formula I:wherein Y is F or Br; or a pharmaceutically acceptable salt thereof. The color vision degree coefficient calculating unit calculates a color vision degree coefficient indicating the degree of color vision deficiency. A power control strategy may use one power supply for the master DSP, a second power supply shared between the slave DSPs, and a third power supply shared between each of the SSPC channels. At least one gate, body region and source region are formed above the drift region at, or proximate to, a top surface of a substrate of the semiconductor device.