Light therapy system and method

A light therapy system (12) for administering a controllable melanopic luminous exposure includes a controllable lighting assembly (16) for use in delivering the desired luminous exposure. The system further includes a visual display means (18) for presenting at the same time a visual output such as a video to the patient. A target melanopic luminous exposure for administration to the patient is received by a controller 24. This target is then adjusted to compensate for an additional melanopic luminous exposure which the visual display means generates in displaying the visual output. A control schedule is then generated for controlling an illuminance of the lighting assembly to deliver over a defined treatment period the adjusted target melanopic luminous exposure. The lighting assembly is then controlled according to the control schedule. In this way both the visual output of the visual display means and the light output of the lighting assembly can be administered, while ensuring that the original target melanopic luminous exposure is delivered and not exceeded.