When evaluating patients for glaucoma it is important to evaluate both eyes, because the optic nerves of a healthy individual usually are symmetric, as shown here. Cup-to-disc ratios greater than 0.9 indicate a high level of glaucoma suspicion, while those of 0.6 to 0.8 indicate a moderate level. When using cup-to-disc ratios to assess a level of glaucoma suspicion, it is important to remember that African- Americans tend physiologically to have larger cup-to-disc ratios than Caucasians (based on a larger absolute disc size).