It is generally cloud free in the 'eye' of a typhoon as a result of the convective structure of the storm. The tubular wall of cloud lining the eye of the storm is where windspeed is at its greatest and also the position where air rises most rapidly; this could be understood as resulting from the fact that the [i]pressure gradient [i] is greatest there (i.e. the isobars are really close together there).
But this does not follow! When there is no eye and the air rises most rapidly at the centre (most cyclones), the windspeed still goes to zero at centre (because of symmetry) and the pressure gradient also vanishes there (same reason).