Quantitative analysis of optic disc cupping in compressive optic neuropathy.

PURPOSE

Cupping of the optic disc, a characteristic sign of glaucoma, has been anecdotally described in association with compressive optic neuropathy. The aim of this study is to perform a masked, controlled, and quantitative measurement of the optic disc cup to determine if compressive lesions of the afferent visual pathway were associated with increased cupping.

METHODS

The ratio of cup area:disc area of 29 patients with intracranial lesions impinging on the optic nerves and the chiasm (14 with pituitary adenomas, 7 with meningiomas, 6 with craniopharyngiomas, and 2 with aneurysms) was compared with those of 20 age-matched control subjects. The areal ratios were derived planimetrically from hand-drawn images of magnified stereophotographs. Patients were divided into three groups based on the degree of laterality of visual compromise. Uninvolved eyes served as an internal control for patients with unilateral disease.

RESULTS

The median ratio of cup area:disc area was 0.37 for all eyes with visual compromise (n = 51) and 0.10 for control eyes, which was statistically significant (P = 0.0001). The median intereye difference in the ratio of cup area:disc area was 0.13 for patients with unilateral lesions and 0.04 for control subjects. This difference also was statistically significant (P = 0.0001).

CONCLUSIONS

The finding of intereye asymmetry in patients with unilateral optic nerve compression is convincing evidence that the enlarged cup is an acquired feature. Several types of compressive lesions of the anterior visual pathway can be associated with increased cupping of the optic disc in the absence of increased intraocular pressure.