Nyctalopia, or night blindness, is an impairment of visual acuity specific to scotopic vision, implying a loss or impairment of rod photoreceptor function. Patients may spontaneously complain of a disparity between daytime and nocturnal vision, in which case acuity should be measured in different ambient illumination.
Nyctalopia may be a feature of: Retinitis pigmentosa
Vitamin A deficiency
Cancer-associated retinopathy: most commonly associated with small-cell lung cancer (antirecoverin antibodies may be detected), though gynecological malignancy and melanoma have also been associated (with antibipolar retinal cell antibodies in the latter).