Credé's silver nitrate drops for newborns

In 1874 the maternity hospital in Leipzig recorded 45 cases of ophthalmia neonatorum among 323 births, or 13.6 percent. In 1879 it was 36 among 389. The disease, a pus-forming inflammation of the newborn's eyes caught from the mother during delivery, was then a major cause of childhood blindness in Europe. Up to half the children in schools for the blind had lost their sight to it.

Carl Credé, professor of obstetrics and director of the university's obstetric clinic and midwives' school, held that the infection entered the eyes during birth. In October 1879 he began putting a borax solution into the eyes of babies born to mothers judged to be infected, whose vaginas were also rinsed throughout labor. Three of the first 20 babies still fell ill. In December he switched to silver nitrate, 1 part in 40. None of 38 babies treated this way developed the disease by June 1880, but 12 babies of mothers thought healthy, who had been left untreated, did.

From 1 June 1880 every baby was treated. The solution was weakened to 1 in 50, or 2 percent, and no longer squirted in: an assistant gently opened each cleaned eye and a single drop was applied from a small glass rod. From then until 8 December the hospital had 200 births and one case, in a baby whose eyes had been missed by mistake. Credé reported this in Archiv für Gynaekologie in 1881.

Two further reports followed. Over almost three years Credé counted one or at most two cases among 1,160 babies, and he found the same rate a year later, in March 1884, when he gathered the work into a book. Results elsewhere varied. At Späth's clinic in Vienna the rate fell below 1 percent among 1,350 babies, while Hecker in Munich saw almost no change.

The drops irritated the eye, and the strength was later cut to 1 percent. Silver nitrate works poorly against chlamydia, now the more common cause, and the United States and several other countries have replaced it with erythromycin or tetracycline ointment.