MRCP2-3428

A 63-year-old woman presents with a sudden blurring of vision and pain in her left eye. She recalls experiencing reduced sensation in her left leg 6 years ago, which eventually resolved on its own. On examination, her left eye has significantly worse vision and colour discrimination, and she experiences pain with eye movement in all directions. There are no abnormalities found in her neurological examination of the limbs.

What factor is associated with a poor prognosis in the likely diagnosis of this patient?