Box 1.

ISGEO Categorizations used in Glaucoma prevalence studies

Category	Structural Abnormality	Visual Fields Abnormality
1	Eyes with a CDR or CDR asymmetry ≥97.5th percentile for the normal population, or NRR width reduced to ≤0.1CDR (between 11 to 1 o'clock or 5 to 7 o'clock).	Present
2	Advanced structural damage with CDR or CDR asymmetry ≥99.5th percentile for the normal population	Not proven
3	Optic disc not seen but visual acuity <3/60 and IOP>99.5th percentile or visual acuity <3/60 with evidence of glaucoma filtering surgery or medical records of glaucomatous visual morbidity	Not possible