[Hermann von Helmholtz (1821-1894). On the 100th anniversary of his death].

In Helmholtz's judgement it was a favourable fate to have been thrown under medical students and into medicine with a sense of geometrics and with knowledge of physics. The result of this favourable combination was the invention of the ophthalmoscope and the Handbook of Physiologic Optics. Those were the foundations of all physiological aspects of ophthalmology, which were taken up and completed by A. v. Graefe and his colleagues. The ophthalmoscope was invented on the occasion of his university-courses, when Helmholtz tried to explain the theory of the red reflex of the pupil. Stimulated by Helmholtz in the following year Ruete developed the method of indirect ophthalmoscopy. This method at once was simplified again by Helmholtz in an extraordinary way. These two publications by Helmholtz contain all further developments involved with the ophthalmoscopy as an anticipation. The Handbook of Physiologic Optics is the first encyclopedic monography of this topic. Many new inventions are extremely valuable for the practical requirements of ophthalmologists. The first chapter about dioptrics contains the description of the Ophthalmometer, a new instrument to measure the astigmatism. In the chapter about visual sensations a clear survey about light- and colour sense is given. The colour deficiencies which were found during the decades before are introduced as the most important arguments for the three-component-theory of human colour vision. The prototype of a telestereoscope is demonstrated in the third chapter about visual perception.(ABSTRACT TRUNCATED AT 250 WORDS)