- damage to the optic nerve before the optic chiasm eg compression by tumour
- optic neuritis
- asymmetrical glaucoma
Broadway, D. How to test for a relative afferent pupillary defect. Community Eye Health. 2012; 25(79-89): 58-59.
Pearce, J. The Marcus Gunn pupil. J Neurol Neurosurg Psychiatry. 1996; 61(5): 520.