cup:disc ratio

cup:disc ra·ti·o

(kŭp disk rā'shē-ō)
The ratio between the diameter of the cupped or depressed central zone of the optic disc and the diameter of the entire disc; normally lower than 1:3, it is increased in glaucoma.
References in periodicals archive ?
Although the alterations in cup:disc ratio, optic nerve head pallor, vascular changes and peripapillary atrophy are explained comprehensively, it is a shame that after so much detail, more photographic examples were not provided of abnormal discs.