A method for controlling at least one process parameter of an injection moulding machine comprising a control computer which is connected via a network to a data processing unit of an optical testing system, wherein in addition to the data processing unit of the testing system and the control computer, the network connects further network components for data exchange with one another, comprising the steps: - cyclic production of identical injection-moulded parts using the injection moulding machine, - demoulding of the injection-moulded parts produced from a moulding tool of the injection moulding machine, - conveying all the demoulded injection-moulded parts to the testing system using a conveying device, - recording image data of each injection-moulded part conveyed to the testing system using a digital imaging device of the testing system, - determining useful data from the image data with the aid of the data processing unit, wherein the useful data represent a feature of each injection-moulded part, - repeated statistical analysis and preparation of a continuously changing group of useful data by means of the data processing unit in such a manner that the quantity of useful data of the group is reduced, - repeated transmission of the reduced useful data of each group via the network to the control computer and derivation of control data from the reduced useful data of each group by means of the control computer or - derivation of control data from the reduced useful data of each group by means of the data processing unit and repeated transmission of the control data via the network to the control computer, - wherein the repeated transmission of the reduced useful data or the control data is initiated by an interrogation of the control computer in the data processing unit or by an unrequested sending of the useful data by the data processing unit, - changing the at least one process parameter by means of the control computer depending on the control data. - cyclic production of identical injection-moulded parts using the injection moulding machine, - demoulding of the injection-moulded parts produced from a moulding tool of the injection moulding machine, - conveying all the demoulded injection-moulded parts to the testing system using a conveying device, - recording image data of each injection-moulded part conveyed to the testing system using a digital imaging device of the testing system, - determining useful data from the image data with the aid of the data processing unit, wherein the useful data represent a feature of each injection-moulded part, - repeated statistical analysis and preparation of a continuously changing group of useful data by means of the data processing unit in such a manner that the quantity of useful data of the group is reduced, - repeated transmission of the reduced useful data of each group via the network to the control computer and derivation of control data from the reduced useful data of each group by means of the control computer or - derivation of control data from the reduced useful data of each group by means of the data processing unit and repeated transmission of the control data via the network to the control computer, - wherein the repeated transmission of the reduced useful data or the control data is initiated by an interrogation of the control computer in the data processing unit or by an unrequested sending of the useful data by the data processing unit, - changing the at least one process parameter by means of the control computer depending on the control data.