A device for the preventative photodynamic therapy of secondary cataract has been developed. Disturbance of the epithelial cells of the crystalline lens during the primary cataract surgery and/or their migration thereafter can frequently generate secondary cataract. This can generally be prevented by destroying these epithelial cells. One approach is to expose them to a phototoxic dye which is then activated by selective exposure to light. For this purpose we designed a light distributor furnishing a torus-shaped light intensity profile, allowing for selective destruction of these epithelial cells, while preventing any potentially damaging exposure to other parts of the eye. The size and geometry of the device are adapted to the eye's anatomy, providing a relatively homogeneous irradiation of the treated zone of up to about 2.7 J/cm(2) in I min. The device is easy to handle and is sterilisable with ethylene oxide gas.