The advent of the incandescent bulb transformed the design and construction of the ophthalmoscope. Instead of using an external and remote source of illumination the instrument became self-luminous. This did not mean that the non-luminous ophthalmoscope disappeared. Far from it; many designs were still being catalogued in the 1930s. In Japan even as late as 1912 the Ando sun ophthalmoscope appeared. As its name implies this relied on the sun's rays as its source of illumination.
An example of a Marple battery-handled ophthalmoscope, supplied by George Spiller Ltd of Wigmore Street, c.1915
With these two advances it was no wonder that the ophthalmoscope became more sophisticated.
Development in the first 20 years of the new century was dominated by an instrument maker, Henry DeZeng, of Camden, New Jersey. Others who were to make a major contribution in this period were Dr Wilbur Marple, Charles H. May of New York and Alvar Gullstrand of Sweden.
DeZeng was a prolific inventor of many eye and ear, nose and throat instruments but his first love was the ophthalmoscope. This is reflected in his many patents. He made the first practical electric ophthalmoscope, the first with a non-corrosive mirror, the first with illuminated lens indicating numbers and the first commercially produced ophthalmoscope with a battery contained in the handle. The list goes on, including being the first to use filters, a rheostat and standard commercial lamps. The DeZeng Company became part of American Optical in the early 1920s: Henry ended his career with a flourish, producing the Professional and the wonderfully named Knickerbocker ophthalmoscopes!
In 1906 Dr Marple presented his new electric ophthalmoscope to the American Ophthalmological Society. The main characteristic was a U-shaped mirror which, he claimed, eliminated the central corneal reflex and the shadow in the lower half of the fundus.
The U-shaped mirror is still present on this Swanzy-Marple ophthalmoscope head dating from 1925.
In 1910 Gullstrand, Swedish ophthalmologist and Nobel Laureate, produced his hand-held monocular and binocular ophthalmoscopes and a year later his large stand-mounted, reflex-free ophthalmoscope. The Gullstrand optical design was to nurture important advances in fundus photography with the Nordensen camera in 1925. Although the Laurence and Heisch ophthalmoscope, built in London the following year, was significantly easier to use, the binocular indirect method of ophthalmoscopy did not catch on until the middle of the twentieth century.
The period between the two world wars was characterised by a flurry of more complex ophthalmoscopes, many of them British innovations, using bulbs of a higher voltage.
Head of a combined Turville-Stewart instrument British Pat No 286793
Post-war example of a Westminster ophthalmoscope
In the USA, Jonas S. Friedenwald introduced his model in 1928 through the American Optical Company. His instrument was large and very long, at over one foot (30cm). Like the Turville-Stewart and other instruments being introduced at this time, it was multifunctional. American Optical was already busy with its new Giantscope, which incorporated a polarising system to eliminate annoying corneal reflections. Meanwhile, in 1928, a departure from the normal head-and-handle ophthalmoscope was taking place in Berlin. Walter Thorner, in conjunction with the Emil Busch Company, patented a radical design of ophthalmoscope, which made ophthalmoscopy reflex-free in a small instrument. He constructed two models, one a hand-held monocular and the other a binocular ophthalmoscope which could either be hand-held or mounted on a table stand. The Zeiss Company acquired Busch in 1948 and continued to produce the monocular version.
|Reflex-free = reflection-free. A reflex is an image formed by reflection. Typical reflexes that need to be overcome in ophthalmoscopy include those of the cornea, fovea (not usually visible in older patients) and fundus - when a red glow appears in the plane of the pupil. In cases of dense cataract the fundus reflex is notably absent.|
C.H.Keeler, FBOA (1903-1993)
After a period of concentration upon contact lenses, including spearheading the introduction of ophthalmic Zelex as an impression moulding material, he returned to instrument design, securing numerous patents between 1949 and 1976. He was awarded the OBE in 1969 for services to the partially sighted.
In 1929 Charles Keeler, then only 27 years old, introduced the Decagon, also known as the Master ophthalmoscope. This was the most complex and comprehensive hand-held ophthalmoscope to be put on the market up to that time. It brought two new functions to an ophthalmoscope, these being the estimation of refractive error (including astigmatism) and the precise location and measurement of any object within view of the fundus.
The Decagon consisted of a Morton magazine of lenses and, on the reverse of the instrument, a circular drum containing a choice of five optical systems for: 1) direct ophthalmoscopy, 2) retinoscopy and indirect ophthalmoscopy, 3) small beam concentration used for searching for opacities in the media, 4) projection of a reflecting graticule with axis determination in astigmatism and 5) the Morgan retinal graticule for locating and measuring any object seen on the retina. Filters, including red-free, white light, daylight and yellow, could be used with any of these systems.
At the same time Edgar Fincham, who with his brother Walter formed a pair of the most brilliant optical lecturers and ophthalmic instrument designers of his generation, patented and had constructed by the Elliott Optical Company his 'ophthalmo-retinoscope'.
The Keeler Company continued its development of more complex ophthalmoscopes with the Cardell polarised ophthalmoscope in 1935. The distinction of this instrument was its use of Nicol prisms to eliminate corneal reflexes. Unlike polarising filters, there was little loss of light. The Iceland spar used in the Nicol prism was cut and assembled in such a way that it allowed the plane-polarised light to be freely transmitted. This was achieved in the Cardell ophthalmoscope by the use of a pair of Nicol prisms, one of which lay in the path of the illuminating system and the other on the viewing axis. A later edition of the Cardell ophthalmoscope was to appear in 1950, but this used Polaroid filters due to a shortage of Nicol prisms, as a result of post-war difficulties in obtaining such material.
1947 was a significant year in the history of the ophthalmoscope for it was at this time that Charles Schepens of Boston constructed his first binocular indirect ophthalmoscope. This method of examining the fundus was to revolutionise retinal surgery and, as was said at the time, this single invention advanced indirect ophthalmoscopy more than had been achieved in the past fifty years. It soon became the standard method of clinical ophthalmoscopy by ophthalmologists.
Looking back in time
The first binocular indirect ophthalmoscope had been invented half a century before Gullstrand, by Marc-Antoine Giraud-Teulon of France (1861). Because of the difficulty in its use, mainly as a result of the weak source of illumination provided by the gas lamp, it and other binocular models were never popular.
The picture shows a Giraud-Teulon ophthalmoscope signed by Nachet of Paris.
|Indirect ophthalmoscopy using a Fison head-worn instrument and a condensing lens held near the patient|
In 1959 Lorimer Fison of Moorfields Eye Hospital, working with the Keeler Company, introduced the Fison binocular indirect ophthalmoscope which was a light and simple-to-use instrument, starting an unbroken line of popular indirect ophthalmoscopes models for the company.
In 1965 Medical Instruments Research Associates (MIRA) of the USA produced the first small pupil binocular indirect ophthalmoscope under Schepens' and Oleg Pomerantzeff's direction. By an ingenious adjustment of the visual and light paths it was possible for the operator to visualise the fundus binocularly and, with a degree of stereopsis, through the smallest of pupils.
|AO monocular indirect ophthalmoscope, 1968|
Direct ophthalmoscopy demonstrated by
From the introduction of Schepen's binocular indirect ophthalmoscope until the present day, the popularity of indirect ophthalmoscopy has increased to such an extent that the hand-held direct ophthalmoscope is hardly used by ophthalmologists, but it remains a popular item of equipment for the optometrist.
As Schepens and others were teaching the advantages of indirect ophthalmoscopy with its wide field of view and stereoscopic vision, further complex direct ophthalmoscopes with powerful illumination were being introduced.
Amongst these were two from the Keeler Company, the Measuring in 1951 and the Pantoscope in 1952. Each of these instruments was powered by a 12 volt precentred bulb with a plano top to eliminate striations in the glass. The Measuring ophthalmoscope had an optical collimator that allowed various graticules to be focused sharply on the fundus. Graticules such as the Morgan 'grid' (for estimating and plotting a retinal detachment) and the Neame (for the precise estimation of blood vessel diameter) were part of the six graticules included. The Pantoscope was a multipurpose instrument for direct, indirect and small pupil ophthalmoscopy. The instrument also had a strong adjustable slit beam, polarising filters and other accessories such as an attachment for examining eyes with high myopia.
Striation 'Striae' = streaks in optical glass. They may occur due to contamination during the manufacturing process or indicate imperfectly mixed base materials.
Graticule = a transparent graduated scale which can be engraved or photographically printed onto the front focal plane of an optical instrument so the user can measure the apparent dimensions of the object under view.
New sources of light and ever smaller instruments
|Zeiss Jena Electric Ophthalmoscope|
Their life was to be curtailed suddenly, however, by the introduction of a new type of light source by the Welch Allyn Company in 1973. This was the halogen bulb, operating at 3.5 volts and producing a brilliant white light. The new generation of ophthalmoscopes used rechargeable batteries and was to be far less complex in construction and operation.
From the late 1970s to the present day all the major ophthalmoscope manufacturers have used halogen or similar bulbs. The Keeler Company converted its popular 'chain of lenses' Specialist ophthalmoscope (first introduced 1955) to Halogen illumination whilst Heine of Germany used its own kryptogen bulb for its Miroflex and Autofoc ophthalmoscopes. The latter instrument, first introduced in 1973, had an automatic synchronised focus arrangement whereby the illumination and Rekoss disc were coupled so that the aperture and graticules were always sharply in focus on the fundus. Enclosed, dust-free optics is now considered an important feature and is employed by the leading manufacturers.
Miniaturisation in the form of the mini or pocket ophthalmoscope, started by Welch Allyn, has become a useful addition to the practitioner's armamentarium. The choice is wide, not only with the manufacturer, but in sophistication, varying from a no-frills instrument to instruments indistinguishable from their bigger brothers but for the small handle.
The picture shows a Welch-Allyn all-plastic, small-handled ophthalmoscope in a fetching green colour.
Almost exactly 150 years after Helmholtz made public his discovery to the Berlin Physical Society on 6th December 1850, the Welch Allyn Company came out with a totally new design of ophthalmoscope called the Panoptic. This hammer-shaped instrument is held against the patient's orbit and produces a direct image of 25 degrees field of the fundus, some five times wider than the conventional direct ophthalmoscope. The patented optical design converges the illumination to a point at the cornea, allowing easy entry through small pupils.
Many other diverse forms of ophthalmoscope have appeared over the years. Mention should be made perhaps of the ophthalmoscope's role in pleoptics, with the Visuskop and Euthyscope by Oculus (1958) and in the first hand-held Ruby laser by Keeler, in 1964. For the future one might anticipate the use of advanced electronics, such as in the scanning laser ophthalmoscope for the sophisticated end of the market, and lifelong sources of illumination such as light-emitting diodes (LEDs) in the more basic forms of instrument.
Pleoptics = A therapeutic method of treating amblyopia by dazzling part of the retina with intense light whilst protecting the fovea so as to correct eccentric fixation.
One of the earliest exponents and enthusiasts for the ophthalmoscope was the American Edward Loring. He wrote a sentence in the opening chapter of his Textbook of Ophthalmology in 1892 which seems an apt conclusion:
In the whole history of medicine there is no more beautiful episode than the invention of the ophthalmoscope, and physiology has few greater triumphs
Some Useful Sources for Historians of Ophthalmoscopes and Retinoscopes:
All these titles are available in the BOA Library or within the files of the BOA Museum.