Invasiviness
Invasive methods: Intravitreal, Subconjonctival
Semi-invasive methods: Subtenon, Periocular
Non-invasive: Iontophoresis, Topical gel or solution
When I mean "semi-invasive", I mean that the needle does not perforate the globe and the product is injected in the orbit, around the globe so it reduces the risks (Alcon has chosen that kind of administration for Retaane for example)