Fertility of blind women.

Light and light-dark cycles have a marked effect in regulating the reproductive cycles of some mammals. During long nights and short days or after blinding, gonadal atrophy will occur in the Syrian Golden hamster, Mesocricetus auratus . This phenomenon has been shown to be mediated by stimulation of the pineal gland .' Moreover, the light-dark cycle may have a similar endocrine effect in human beings under certain circumstances. For example, in northern Finland most conceptions occur during the summer .2 However, a preliminary study of blind women indicated that blindness seems to have no longterm effect on fertility . 3 The present study includes data from the preliminary study as well as additional data gathered since that time .