Diplopia, visual loss, and pupillary asymmetry are important presentations of neuroophthalmologic emergencies. When evaluating a patient with diplopia, the most important initial step is to determine whether the diplopia is monocular or binocular. Binocular diplopia resolves when either eye is covered. Monocular diplopia usually results from ophthalmologic causes or refractive errors. Binocular diplopia results from ocular misalignment. Diplopia is most pronounced when looking in the direction of the limited extraocular movement regardless of cause. Neuro-ophthalmologic visual loss is divided into prechiasmal, chiasmal, or postchiasmal etiologies. Monocular visual loss indicates a lesion anterior to the chiasm. Pupils are evaluated for reactivity and size in light and dark environments. Anisocoria is defined as unequal pupil size. A significant percent (approximately 20%) of the population has minimal anisocoria without pathology, termed physiological or simple anisocoria. Only physiological anisocoria or Horner's syndrome produce anisocoria with normally reactive pupils.