Ranibizumab (trade name Lucentis) is a monoclonal antibody fragment derived from the same parent mouse antibody as Bevacizumab (Avastin). It is much smaller than the parent molecule Avastin; it has been manufactured to provide stronger binding to Vascular Endothelial Growth Factor (VEGF). 

Ranibizumab binds to and inhibits a number of subtypes of VEGF.  VEGF triggers the growth of new vessels, which may leak blood and fluid into the retina. These leaky blood vessels result in the wet type of AMD.

 

Prior to Lucentis intravitreal treatment (left), subretinal fluid (black area under retina profile) is present.

One month after treatment (right), subretinal fluid has resorbed and vision has improved.