Macugen hæmmer et stof kaldet VEGF (Vascular Endothelial Growth Factor), som får blodkarrene til at vokse og desuden forårsager væskelækage fra karrene samt hævelse.
Macugen blocks a substance called Vascular Endothelial Growth Factor which makes the blood vessels grow, and also causes fluid to leak from the vessels and swelling.