Which condition is a common cause of sudden painful unilateral loss of vision?

The condition that characteristically presents with sudden, painful, unilateral loss of vision is optic neuritis. This condition is often associated with multiple sclerosis and is due to inflammation of the optic nerve, which results in damage to the myelin sheath surrounding the nerve fibers. Patients typically experience a rapid onset of visual loss, which can be accompanied by pain, especially during eye movement. This pain arises from the irritation and inflammation of the nerve and often precedes the visual loss.

In contrast, the other conditions listed have different presentations. Cataracts usually lead to gradual vision loss, and while they can eventually cause significant visual impairment, they are typically not associated with sudden onset. Vitreous hemorrhage can cause a sudden loss of vision, but it usually presents with more floaters or shadows rather than discomfort. Central retinal artery occlusion can lead to sudden vision loss as well, but it is typically painless and characterized by a specific presentation, such as a pale retina and a "cherry-red spot." Thus, optic neuritis is distinct due to its combination of rapid visual decline and accompanying pain.