Quantitative analysis of optic disc cupping in compressive optic neuropathy

Area of Science:

• Ophthalmology
• Neurology
• Neuro-ophthalmology

Background:

• Optic disc cupping is a hallmark of glaucoma.
• Anecdotal evidence suggests a link between optic disc cupping and compressive optic neuropathy.
• Quantitative assessment is needed to confirm this association.

Purpose of the Study:

• To quantitatively measure optic disc cupping in patients with compressive lesions of the afferent visual pathway.
• To determine if intracranial compressive lesions are associated with increased optic disc cupping.
• To differentiate cupping caused by compression from glaucoma-related cupping.

Main Methods:

• A masked, controlled study comparing 29 patients with intracranial lesions (pituitary adenomas, meningiomas, craniopharyngiomas, aneurysms) to 20 age-matched controls.
• Optic disc cup-to-disc area ratios were measured planimetrically from magnified stereophotographs.
• Patients were grouped by laterality of visual compromise; uninvolved eyes served as internal controls.

Main Results:

• Eyes with visual compromise due to compressive lesions showed a significantly higher median cup:disc area ratio (0.37) compared to control eyes (0.10) (P=0.0001).
• Patients with unilateral lesions exhibited a significantly greater intereye difference in cup:disc area ratio (0.13) than controls (0.04) (P=0.0001).

Conclusions:

• Increased optic disc cupping is an acquired feature associated with unilateral optic nerve compression.
• Compressive lesions of the anterior visual pathway can cause optic disc cupping independently of elevated intraocular pressure.
• This finding helps differentiate compressive optic neuropathy from glaucoma.