Amaurosis (from a Greek word meaning obscure), the term applied in past days to signify any form of blindness, the cause of which was unknown. The invention of the ophthalmoscope, however, by means of which the fundus or back of the eye can be critically scrutinised by the physician or surgeon, has led to great advances being made in our knowledge of the causes of blindness. There are, however, a few conditions in which the vision is very defective, and yet no abnormal appearance can be detected in the fundus of the eye. One of the commonest of these is met with in cases of squint due to hypermetropia (q.v.); again, in the night blindness of those who have been habitually exposed to strong light, and in some cases of sight failure after railway accidents, little if any change can-be detected with the ophthalmoscope. After exhausting illness, in anaemia, and in some forms of hysteria, a similar condition obtains. A curious form of amaurosis is that known as tobacco amaurosis or tobacco amblyopia, the characteristic feature of which is that the central part of the field of vision is the first to fail. This defect is not uncommonly associated with excessive smoking, but possibly other causes are at work as well, the subject being up to the present time in no very settled state. Finally, amaurosis is at times simulated by impostors. The vacant gaze of the patient who cannot see is very characteristic. The pupils are dilated, the eyes do not converge to fix near objects, but remain as though intent on something in the far distance. This condition is known as the "amaurotic stare." The treatment of amaurosis is unsatisfactory. In the hypermetropia much can be done if the condition has not advanced too far, and some of the tobacco cases improve under treatment when smoking is discontinued.