Quantitative relationship between cupping of the optic disc and visual field loss in chronic simple glaucoma.

The extent of cupping was measured from optic disc photographs of 300 patients with ocular hypertension and suspected or established chronic simple glaucoma, and their visual fields were recorded. The incidence of field defects increased as the vertical cup:disc ratio increased, a value of 0-70 for this ratio being a particularly useful guide to the presence or absence of field loss. There was a significant correlation between the extent of cupping and the size of the visual field. The vertical cup:disc ratio was the most useful quantitative index of cupping.