Which examination finding is characteristic of glaucoma?

The characteristic examination finding for glaucoma is an increased cup-to-disc ratio. In the context of glaucoma, this refers to the ratio of the diameter of the optic cup (the central depression in the optic disc) to the diameter of the optic disc itself. In healthy individuals, this ratio is typically less than 0.3. However, in glaucoma, especially in open-angle glaucoma, increased intraocular pressure can lead to optic nerve damage and result in an increased cup-to-disc ratio, often exceeding 0.5. This finding is crucial in diagnosing and monitoring the progression of glaucoma, as it indicates possible damage to the optic nerve.

The other options may present in various ocular conditions but do not specifically point to glaucoma. Decreased visual acuity, for instance, can occur in many different eye diseases and conditions, while distorted vision is more associated with conditions such as macular degeneration. Involuntary eye movements might signal issues like nystagmus or other neurological conditions unrelated to glaucoma. Thus, the increased cup-to-disc ratio serves as a critical, distinguishing feature specifically linked to the diagnosis of glaucoma.