To see all protocols that comply with the WHO Essential Medicine List 

Grade 1: asymptomatic

Grade 2: exudative and visual acuity 20/40 or better

Grade 3: Rhegmatogenous or exudative detachment; operative intervention indicated; decline in vision (worse than 20/40 but better than 20/200)

Grade 4: Blindness (20/200 or worse) in the affected eye

Reference: Common Terminology Criteria for Adverse Events (CTCAE) Version 4.0 Published: May 28, 2009 (v4.03: June 14, 2010)