I'm rather sure that 7.5mw/cm2 refers to the power density delivered to the surface of the brain after holding the variability of scalp/skull thickness. There are detailed calculations if you look in the patent above Table 1 you will see they used 358-568 mW/cm2 at the scalp to achieve a target of 10mw/cm2 at the brain.Even so, it seems I am within the safe range, unless my calculations/understanding are incorrect (they may well be, as I'm not used to this kind of thinking!). Hmmm looking now back it seems the laser itself had a power density of 7.5mW/cm2, much lower than the energy density of the vetrolaser.
Here is a direct quote,
Taking into account the attenuation of energy as it propagates from the skin surface, through body tissue, bone, and fluids, to the subdermal target tissue, surface power densities preferably between about 10 mW/cm2 to about 10 W/cm2, or more preferably between about 100 mW/cm2 to about 500 mW/cm2, will typically be used to attain the selected power densities at the subdermal target tissue.
If you're still a bit concerned (like I am) then limit your exposure time to only 10-15 seconds at a time.