Table 1.
ISGEO scheme for definition and classification of glaucomatous optic neuropathy13
| Glaucoma | Suspect glaucoma |
| Category 1* (structural and functional evidence) Eyes with CDR or CDR asymmetry ⩾97.5th percentile for the normal population combined with a visual field defect consistent with glaucoma. | Disc suspects. Those who met category 1 (but not category 2) disc criteria, but were not proved to have definite field defects. Field suspects |
| Those with definite field defects, but not meeting category 1 disc criteria | |
| Category 2* (advanced structural damage where reliable field testing is not possible) Eyes with CDR or CDR asymmetry ⩾ 99.5th percentile for the normal population | Those with optic disc margin haemorrhages |
| Those with an IOP ⩾97.5th percentile | |
| Category 3 (optic disc not seen because of media opacity) | Those with an occludable drainage angle (defined as one in which the pigmented/posterior trabecular meshwork could be seen for less than 120° of the angle circumference) |
| (A) The visual acuity < 6/60 and the IOP >99.5th percentile (32 mm Hg) or | |
| (B) The visual acuity < 6/60 and the eye shows evidence of glaucoma filtering surgery |
ISGEO, The International Society for Geographic and Epidemiological Ophthalmology.
*In diagnosing category 1 or 2 glaucoma, it was required that there should be no alternative explanation for CDR findings (dysplastic disc or marked anisometropia) or the visual field defect (retinal vascular disease, macular degeneration, or cerebrovascular disease). Diagnosis was hierarchical: category 1 diagnosis was made in preference to category 2, and category 2 was diagnosed in preference to category 3.