In “monthly PRN” regimes for wet AMD, patients are seen every month and treated if disease is active. In “treat and extend” regimes, patients are injected at each visit, but the frequency of visits is altered depending on disease activity.

Real world outcomes on “treat and extend” have recently been published from a large cohort of patients in Australasia – the visual results are good:

http://www.ncbi.nlm.nih.gov/pubmed/?term=ophthalmology+122%3A1212