Photodynamic therapy involves the injection of a light-sensitive medicine called verteporfin into a vein in the arm.

BBC: Age-related macular degeneration

One was Visudyne (verteporfin), the first drug treatment for severe forms of macular degeneration, the leading cause of blindness.

FORBES: Reviving Novartis

Verteporfin, marketed by the drug firm Novartis as Visudyne, aims to stop the progressive loss of vision associated with wet AMD.

BBC: Blindness therapy row