A device (30) for optimizing the cooling in a gas turbine of the type comprising at least one compressor, equipped with a combustion chamber (10) and an outer casing (16) and inner casing (32), at least one turbine wheel (14), equipped with a series of blades 12), and at least one high-pressure rotor (38), equipped with one or more supporting bearings (34), the compressor being capable of generating cooling air sent to the turbine wheel (14) through a suitable channel (20). On the outer surface of the device (30), there are one or more grooves (26) which allow the passage of additional flow-rates of air from the compressor towards the channel (20), in order to increase the overall cooling air flow towards said turbine wheel (14). The device (30) can be easily installed without the necessity of dismantling the outer casing (16), and is assembled on pre-existing machines in substitution of the vent tube (22) of the seals (36) of the supporting bearings (34).