The cup-disc ratio. The findings of tonometry and tonography in the normal eye.

In eyes with normal fields, the cup/disc (C/D) ratio was found to be significantly related to applanation pressure PAlevel, ratio of pressure reading at the beginning of the tonogram and the tonographic estimate of aqueous outflow activity (Po/C), and C-value. The frequency of C/D > 0.3 increased significantly with the PAlevel and with the magnitude of the Po/C ratio. It increased also as the C-value became smaller. This relationship was independent of age or family history of glaucoma.