SPECIAL ARTICLE The Ophthalmoscope in the Lifetime of Hermann von Helmholtz C. Richard Keeler n the whole history of medicine there is no more beautiful episode than the invention of the ophthalmoscope, and physiology has few greater triumphs.” Thus wrote American ophthalmologist Edward Loring1 in the opening paragraph of his Textbook of Ophthalmology in 1892, 2 years before the death of Hermann “Ivon Helmholtz. On the 150th anniversary of the inven- from Heidelberg, where he had been a pro- tion or “discovery” of the ophthalmo- fessor for 3 years. scope (Figure 1) by Helmholtz, we have Helmholtz told the well-known story an opportunity, once again, to laud this of how 43 years before, he realized that he outstanding physicist of the 19th cen- had solved the mystery of how to pen- tury, just as his peers did on the 10th, 50th, etrate the black pupil of the eye and view and centennial years of this greatest of oph- the fundus. In 1851, Helmholtz had pub- thalmological inventions. lished his Beschreibung eines Augen- Prior to his invention, ophthalmolo- Spiegels,2 which gave a full account of the gists could not view the posterior section optical principles involved. Later he of the eye and struggled to explain cer- proudly told his father that he had re- tain classes of eye disease in which there ceived 18 orders for his instrument from was a dimness or loss of vision. Suddenly throughout Europe. in 1851, the world of ophthalmology was By the time of his death, a great num- taken by surprise, and a new epoch be- ber of different ophthalmoscopes had ap- gan. Immediately after the discovery of peared, many of them designed by the most the ophthalmoscope, men such as Albert eminent ophthalmologists of the day. Lor- von Graefe in Berlin, Germany, Edward ing, in the introduction to his textbook, Jaeger in Vienna, Austria, and William states, “[A]lmost every ophthalmologist has Bowman in London, England, started us- taken a hand in perfecting or at least alter- ing it. Every look into the eye became a ing the instrument, and from the first I have, discovery. perhaps, done more than my share.”1(p2) In 1893 at age 72 years, a year before There were no less than 140 instruments he died, Helmholtz went to America to at- on exhibition at a meeting hosted by Harry tend the World’s Fair in Chicago, Ill, as a Friedenwald and Casey Wood in Atlantic representative of the German govern- City, NJ, on the 50th anniversary of the in- ment. On his way back, he was invited to vention of the ophthalmoscope.3 New York, NY, by Professor Herman Helmholtz did not readdress the con- Knapp to inaugurate his new clinic be- struction of the ophthalmoscope but in- fore an audience of students and mem- stead became the greatest physicist and bers of the medical profession. Professor physiologist of the time. He had demon- Knapp, a former pupil who had begun strated that there were 3 essential ele- studying medicine in Germany the very ments to the working of an ophthalmo- year that the ophthalmoscope was in- scope: a source of illumination, a reflecting vented, had moved to New York in 1868 surface to direct light toward the eye, and a means of correcting an out-of-focus im- From the Royal College of Ophthalmologists Museum and Library, London, England. age on the fundus. (REPRINTED) ARCH OPHTHALMOL / VOL 120, FEB 2002 WWW.ARCHOPHTHALMOL.COM 194 ©2002 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/27/2021 SOURCES OF ILLUMINATION It was the lack of a strong, stable source of illumination that held up the development of the ophthalmo- scope in the 19th century. Early users of the Helmholtz ophthalmoscope had to put up with a naked flickering candle as a light source. During this first decade, the candle was largely replaced by the oil lamp and then the paraffin- burning lamp. Various valiant attempts were made at this time to allow the source of illumination to follow the move- ments of the ophthalmoscope: the first by Ricardus Ulrich in 1854 with his candleholder precariously at- tached to the observation tube,4(p40) and the second by Lionel Beale in 1869 with his built-in oil lamp.5(p97) Figure 1. Early model of the Helmholtz ophthalmoscope, 1851. Late in the 18th century, Swiss- born physician and chemist Aime´ Ar- gand had invented a device that was to evolve into the most common source of illumination during the second half of the 19th century: the gas lamp. In the ordinary oil lamp, combustion was not complete. Ar- gand’s improvement was the replace- ment of the conventional wick with a ring. The flame became a hollow cylinder with a current of air ascend- ing through the inside so that the burning surface was doubled. Ar- gand’s brother accidentally discov- ered that a glass cylinder placed as a chimney over the flame steadied it, created a draft, and allowed the flame to yield the maximum amount of light.6 The gravity-fed oil lamp was fol- Figure 2. Nineteenth-century gravity-fed oil lamp (left) and gas lamp (right). lowed by the gas-burning lamp, which worked on the same prin- New York ophthalmologist, dem- ety of the United Kingdom, it never ciple (Figure 2); by 1869, this source onstrated this new technology at the went into production.8 Sir James of illumination had become the stan- American Ophthalmological Soci- McKenzie Davidson of Aberdeen, dard. This was fine for examinations ety when he presented the first oph- Scotland, who was one of the early in a fixed location such as an oph- thalmoscope that used an electric pioneers of the use of x-ray in oph- thalmologist’s office or the hospital, bulb.7 It was not a success, mainly thalmology, published an article in but for domiciliary visits the por- because of the unreliability and short the Lancet of January 1886 show- table candle or oil lamp, such as the life of the bulb. ing a diagram of an electric ophthal- one devised by Joseph Priestley Smith The following year saw the moscope.9 The third electric oph- of Birmingham, England,4(p270) was emergence of 3 ophthalmoscope de- thalmoscope was designed by Henry used well into the 20th century. These signs incorporating electric bulbs. Juler of London, England. Unlike lamps incorporated a reflecting mir- Like Dennett, Thomas Reid of Davidson’s concept, Juler’s instru- ror behind the candle and a strong Glasgow, Scotland, placed a bulb in- ment went into production. convex lens in front to condense the side the column of his instrument, Juler’s design (Figure 3) was light. but he used a prism instead of a mir- the attachment of a light source to In 1879, Thomas Edison was ror to project the light. Although this the outside of the ophthalmoscope working on the incandescent bulb. model was shown at the 1886 meet- body, close to the mirror with the Six years later William Dennett, a ing of the Ophthalmological Soci- bulb pointing toward the center ap- (REPRINTED) ARCH OPHTHALMOL / VOL 120, FEB 2002 WWW.ARCHOPHTHALMOL.COM 195 ©2002 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/27/2021 the second model by Coccius,11(p42) but it did differ in 2 important re- spects: the mirror was convex and B was made of metal, not glass. Metal provided sharp edges to the sighthole with no restrictive viewing canal, which often occurred when using thick glass mirrors. Professor G. Theodor Ruete of Leipsig, Germany, was the first to in- troduce a concave mirror with aper- A ture, in 1853. This method of reflect- ing light toward the eye was to last the whole of Helmholtz’s lifetime and well beyond. Ruete used this con- cave focusing mirror in his new in- direct ophthalmoscope (Figure 5), a method of ophthalmoscopy13 that C Helmholtz had anticipated and that was to prove of extraordinary impor- tance in ophthalmology. Most oph- Figure 3. Juler electric ophthalmoscope thalmoscopes thereafter accommo- showing the driving wheel (A) that moves the dated mirrors and lenses, allowing the lenses around the track, the lamp housing (B) containing the bulb, and the Le Clanche´ battery ophthalmologist to switch between (C) that powers the small lamp. direct and indirect ophthalmoscopy on the same instrument. erture. Apart from excessive sight- In 1854, Edward Jaeger of Vi- hole flare, this instrument had the Figure 4. The first ophthalmoscope by Adolf enna, Austria, introduced an oph- same problem of a short bulb life. Coccius, with a plano-mirror and biconvex lens thalmoscope with a choice of aper- for focusing the light. However, various models using this ture mirrors with a 4- or 7-in focal method became popular. length as well as his version of Helm- used only for direct ophthalmos- holtz’s glass plates, each of which METHODS OF copy, and the vogue for the indi- could be angled toward the source REFLECTING LIGHT rect method had caught on rapidly. of illumination.4(p102) Jaeger thereby His glass plates method of light combined the principles of Helm- Haynes Walton10 of St Mary’s Hos- reflection was quickly superceded holtz, Ruete, and others in one rather pital in London wrote in his Practi- when Epkens, an instrument maker complicated instrument. cal Treatise on the Diseases of the Eye in Holland, followed by others, used A common problem in all oph- in 1875, “The modes of reflecting a plano-mirror with an oval-shaped thalmoscopes when tilting the mir- light into the eye are manifold.