Drug concentration at desired location is limited by low percentage that reaches the target and/or potential side effects and complications in other parts of the eye that preclude higher doses.
Invasive surgical approaches must be performed in an operating room which increases cost, reduces access, and delays treatment (with potentially irreversible consequences).
Negative effects of poor outcomes and exposure to difficult surgical interventions with awkward recovery protocols and potential long-term consequences (i.e. cataract formation).