@asad
wslam
ya there r few things u can check:
make sure that the head lights are clean, i.e no dirt on the inside of the transparent plastic cover of the light.
u can check the wattage of the tubes you r using, higher wattage means higher intesity(brightness).
if the tubes r 3~4 yrs old, replace them. tubes usually lose the optimum brightnes after some time.
make sure that the reflecting(chrome) surface is not corroded or has not lost its shine. if so, lights can be replaced or chrome coating can be refurbished.
cheers!