Allvar Gullstrand is still an inspiration

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One hundred years after the Swedish ophthalmologist Allvar Gullstrand received the Nobel Prize for Medicine, his teachings and contributions to the science of optics are still relevant and inspiring to modern practitioners, Thomas Olsen MD told delegates in a special Gullstrand Lecture given at the XXIX Congress of the ESCRS.

'Allvar Gullstrand was the first and to date the only ophthalmologist who has been awarded a Nobel Prize. Together with other giants from the birth of modern science, like Hermann von Helmholtz, he applied the theory of physical mathematics to the study of ocular refraction. Among his achievements are numerous scientific papers on optical instrumentation and modelling of the human eye and many of his methodologies and schematic eye assumptions are still valid today,' he said.

In his lecture, Dr Olsen, assistant professor at the University Eye Clinic of Aarhus, Denmark, paid tribute to the life, work and lasting legacy of one of the true pioneers of refractive optics, whose inventions are still in use in ophthalmic practices today.

'One such example is the slit lamp which Gullstrand invented as a tool to study the interfaces of the ocular media. Yet another example is his invention of the reflex-free ophthalmoscope, the principle of which is still in use in modern fundus cameras,' Dr Olsen said.

[caption id='attachment_606' align='alignright' width='300' caption='Hermann von Helmholtz'][/caption]

Dr Olsen said that Gullstrand's most important contribution, however, was probably his theoretical work to pave the way for a complete understanding of the human eye as an optical system. In delving into subjects such as real ocular imagery, corneal optics, astigmatism, spherical aberration, accommodation, and the gradient index of refraction of the crystalline lens, Gullstrand helped to significantly advance the state of knowledge on the structure and function of the human optical system.

Born in 1862 in Landskrona, Sweden, Gullstrand started his medical studies in 1880 at Uppsala University, paid a one-year visit to Vienna in 1885, finally returning to Sweden and graduating from Stockholm University in 1888. In 1890, he wrote his thesis on the theory of astigmatism and in 1894 he was appointed the first professor of ophthalmology at Uppsala University. Gullstrand was entirely self-educated in the fields of geometric and physiological optics and in 1909 he published the famous chapter 'The Dioptrics of the eye' in Helmholtz's textbook on Treatise on Physiological Optics (3rd edition).

Great inspiration

As Dr Olsen noted, Gullstrand was professionally active in a period of considerable scientific achievement, including major advances in physical science, electromagnetic theory, thermodynamics, atomic particles and experimental design. He was also deeply interested in mathematics and its potential applications for the human optical system.

'Although he never studied mathematics per se, he was 'educated and self-taught' and attracted by the power of this discipline on ocular optics,' said Dr Olsen. 'There is no doubt that a great inspiration for Gullstrand at this time was von Helmholtz. Thanks to him, for the first time it was possible to look into the eye and see what nature had designed for us to see with. Imagine how challenging this would be to someone with a bright mind and a growing knowledge of optics such as Gullstrand.'

[caption id='attachment_608' align='aligncenter' width='600' caption='The Beginning of the 20th century – Birth of modern science - Courtesy of Thomas Olsen MD'][/caption]

Gullstrand's initial work remained largely unknown to his scientific contemporaries, as his first papers describing the optics of the human eye were written in Swedish, followed later by papers in German, the most commonly used scientific language at that time.

The title of his Nobel lecture in 1911 was: 'How I found the mechanism of the intracapsular accommodation', in which Gullstrand set out to describe the physical mechanism behind the accommodative power of the crystalline lens. He also described the methods and logic involved in developing complete optical analysis of the eye, with the human crystalline lens considered as a special case.

Even today, 100 years after its delivery, the Nobel lecture makes very interesting and relevant reading for a modern ophthalmologist, said Dr Olsen.

'For those of us who have been interested in the calculation of IOL power for many years, this is fascinating material. You have to understand the situation – very little was known about the lens of the eye, there was no ultrasound, optical biometry or sophisticated equipment like Scheimpflug imaging, nor was there topography, tomography, wavefront, or aberrometry. What they did have, however, was the science of optics and mathematical skills,' said Dr Olsen.

Gullstrand fully appreciated that as an optical device the eye operated quite differently from cameras or telescopes.

'Thin lens calculations or first order optics were simply not sufficient for a good understanding. In optical terms the eye is a small aperture, short focal length, wide-angle optical system and this makes the eye and the optics very challenging to describe,' said Dr Olsen.

Gullstrand rose to the challenge, however, using differential equations up to the fourth order and setting up complex mathematical models before he felt confident that his schematic eye model would be a realistic one.

The Gullstrand theoretical eye provided exact model data for all components of the optical system, including intraocular distances, indices of refraction of the ocular media, and radii of curvature of the corneal and lenticular interfaces, together with the cardinal points of the eye.

Summing up, Dr Olsen said that Gullstrand was an outstanding thinker and pioneer whose scientific writings are still capable of illuminating and stimulating ophthalmologists in the modern era.

'Allvar Gullstrand knew a lot, but when it came to surgical modalities he could actually do little. His was the era of exact, descriptive science. Today as a corneal or a lens surgeon we can do a lot, but do we actually know what we are doing? This is why it is important to continue to read those old papers because they still have much to teach us.'