Pre-Nineteenth Century History of Optics Motivating Eye Care Technology
Karan R. Gregg Aggarwala, OD (NIH Equiv.), MS, PhD, FAAO
Founder-President, Ben Vision Research, Inc., July, 2013 CE, New York, NY

Introduction
In chronological order by year of birth, this list of famous people (born 1801 or before) and their brief biographies, documents the major achievements of pre-modern philosophers, mathematicians, physicists, scientists and optical engineers-- because of whose pioneering discoveries and inventions, current-day optical, optometric, and ophthalmic instrument development became permissible and was realized. These biographies include people born in, or working-- in Europe, the United States of America, and the Near East. Biographies from other world regions are not in this review.
 
Criteria for Inclusion
The famous people selected in this list of biographies have been selected based on various criteria— some based on my memory of their known contributions, and others based on subject area searches. These criteria may not be comprehensive. The one easily definable item these outstanding personalities share in common is their inclusion in the Hutchinson Dictionary of Scientists1. This inclusion criterion is good but has its problems. For example, Lambert is more famous than Lippershey or Ritter, yet Lambert’s biography was missing in the Hutchinson Dictionary of Scientists and was not present in The Physics Book2.

I did not want to use any internet resource other than www.en.wikipedia.org and when I did not find Lambert there, I decided not to include him. It is likely that there would be many other scientists who may have been omitted in this article. For this, an apology is offered along with the excuse of sourcing consistency.


history of optics ben vision research   history of optics ben vision research   Pythagoras c. 580- 500 BC: An early philosopher and mathematician of ancient Greece, Pythagoras classified numbers and gave them mystical properties.

Born on the island of Samos, he fled a despotic ruler to found a school and brotherhood in Croton, South Italy. The school lasted a little over 50 years until it was suppressed for political and religious reasons.

The Pythagoras theorem equates the square of the length of the hypotenuse of a right-angled triangle to the sum of the squares of the lengths of its perpendicular sides.

Pythagoreans formulated the theory of proportions (ratios and fractions), which helped them understand and describe the harmonic motion of musical strings. Harmonic analysis forms the fundamentals of Fourier-optics, and finds its roots in the work of Pythagoras.
         
history of optics ben vision research    history of optics ben vision research    Euclid c. 330 – c. 260 BC: This famous mathematician used logical steps to deduce known principles of mathematics and geometry from the unknown, by what is known as the synthetic method.

Using analytical techniques, he developed axioms of Euclidean geometry from conjectures and hypotheses.

Euclid set up a school of mathematics in Alexandria (now in Egypt). His works were translated first into Arabic by Alhazen, and then into Latin, and from both of these languages, into various European languages.

Geometry applies directly to optics because light tends to travel in straight lines except under the influence of strong gravitational fields (Einstein’s General Theory of Relativity), or from aperture edge-effects (diffraction), or optical media-interface effects (refraction, reflection).
         
Ptolemy 100 to 170 CE: Born on the banks of the Nile in the town of Ptolemais Hermii, Ptolemy worked in Alexandria in an observatory set up at the top of a temple. Said to be inspired by Plato, Ptolemy worked on the assumption that the earth was shaped like a perfect sphere. The calculation of projections onto a spherical surface has applications in visual field testing (perimetry) and retinal mapping. Ptolemy’s Geography was a standard source of information until the 16th Century— based on his maps of Asia and large parts of Africa. His system of an earth-centred universe was toppled in 1543 by the astronomer Copernicus.
 
history of optics ben vision research history of optics ben vision research
     
Ibn al-Haytham Alhazen 965-1038 CE: Alhazen’s book of optics, Kitab al-Manazir, was translated from Arabic to Latin as Opticae thesaurus (1572). His original comprehensive contributions were based on his experiments and on his study of Greek literature, and were considered authoritative.

Alhazen challenged the view held by Hero and Ptolemy that rays first emerge from the eye, capture the form of the object, and return to the eye as an eidola. Instead he proposed that light emerging from the sun is reflected by objects and enters the eye to produce the sensation of vision.

Alhazen studied the image-forming properties of spherical and parabolic mirrors, and measured the refraction of light by lenses.

His Book of Optics was utilized by near-Eastern philosopher-scientists (e.g. al-Farisi 1267-1320), and Western scientist-monks (e.g. Theodoric 1250-1310), well into the period of the Renaissance.
  history of optics ben vision research   history of optics ben vision research
         
Leonardo da Vinci 1452-1519 CE: Da Vinci received formal elementary education, and was apprenticed at the age of about 14 by his father, to the artist Andrea del Verrocchio4 in whose guidance he learned about artistic, technical and mechanical subjects. Between 1490 and 1495 he produced his well-known notebooks in mirror-writing. Leonardo explored the science of painting and documented the visual cues that lead to monocular depth perception, such as geometric perspective, atmospheric haze, distance and direction of sources of illumination, and length, depth and direction of shadows.

Da Vinci also developed a theory of mechanics based on friction and resistance, with illustrations of gears, screw-based cutting machines, and hydraulic jacks. The total number of inventions attributed to Leonardo is a staggering three hundred!

Leonardo studied the flight of birds, forming the basis for modern avionics. After 1503, he conducted hydrological studies for civil engineering projects and for the circulatory system of the heart, which today form the roots for the study of blood flow dynamics. Da Vinci was born in Tuscany, lived in Florence and Milan, and spent his last years in Rome and Amboise (France).
 
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Hans Lippershey 1570-1619 CE: This German-born Dutch spectacle lens-maker is often credited with inventing the refracting telescope in 1608. Lippershey's original instrument (with 3 times magnification) was termed “Dutch perspective glass,” and consisted of either two convex lenses producing an inverted image, or a convex objective and concave eyepiece leading to an upright image. The term "telescope" was coined three years later by Giovanni Demisiani. The ophthalmic lens industry started in Venice and Florence in the thirteenth century, and later expanded to the Netherlands and Germany. 
 
history of optics ben vision research  history of optics ben vision research 
 
Christoph Scheiner 1573-1650 CE: In about 1605, Scheiner invented the pantograph, an instrument for making scaled copies of schematics. Scheiner built his first telescope in 1611 and projected the image of the sun onto a white screen. His observations of “sunspots” and the attribution to “refraction” of the apparent elliptical form of the sun near the horizon are commendable. Scheiner also proposed that Venus and Mercury revolved around the sun and due to his fear of religious or political adversity his data were communicated under a pseudonym to Galileo and Johannes Kepler. Ophthalmic optical instrument designers are well aware of the “Scheiner disc” which contains a double pin-hole that determines focus of optical systems and can help distinguish between myopic and hyperopic focal planes of the eye.
 
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 history of optics ben vision research   history of optics ben vision research   Willebrord van Roijn Snell 1581-1626 CE: Born in Leiden, Snell developed the method of triangulation in 1615, from which he made an accurate determination of the radius of the Earth.

Calculations of the sagittal depth of spherical lenses are based on the same triangulation formulae.

Snell devised the basic law of refraction- which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.

When the first medium is a vacuum or air, the Snell ratio equals the refractive index of the refracting (second) medium.

Snell’s law was published by the mathematician Descartes in 1637, and forms the basis for all monochromatic refraction by lenses and prisms.
         
 
Isaac Newton 1642-1727 CE: Newton was born in Lincolnshire and studied at Cambridge where he became a professor at age 26. His theories were consistent with the laws of planetary motion developed by Johannes Kepler, and Kepler’s laws helped Newton define the terms mass, weight, force, inertia, and acceleration. Newton and Leibniz worked independently on the development of differential calculus. Newton’s experiments on dispersion of white light through prisms of glass inspired him to minimize chromatic aberration by using mirrors instead of lenses in his telescope. His experiments on light and colour were conducted in a darkened room with a slit-beam of sunlight entering through a window. Besides geometric optics, Newton investigated thin-film interference and gravitation. Robert Hooke claimed to have discovered the inverse-square law of gravitation prior to Isaac Newton.
 
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Benjamin Franklin 1706-1790 CE: The inventor of bifocal spectacles, Benjamin Franklin has been an inspiration to almost all Americans who believe in the values and principles of the founding fathers of the constitution. Aside from his late-life service as ambassador to France and his prior founding of the Post Office, Ben Franklin is famous for his 1752 “kite and key experiment” (considered dangerous to repeat) conducted just prior to a thunderstorm—which proved that lightning is a form of electricity that can be harnessed and stored in a Leiden jar (capacitor). Franklin distinguished between positive and negative electricity, and his observations predate the more quantitative research of Volta (1745-1827) that formed the basis for the flow of electrical current. 
 
It is less commonly known that Benjamin Franklin conducted experiments on thermometer readings underneath sunlight-illuminated cloths of various colours.

These experiments suggested that absorbed visible radiation (light) of varied spectral composition may be specified as elevations in temperature (T).

These experiments relating light and temperature were followed up by Herschell and formed the basis for Max Planck’s quantum theory (1900).  
  history of optics ben vision research    history of optics ben vision research 
         
William Frederick Herschell 1738-1822 CE: Born in Hanover, Germany, William Herschell was an English astronomer and telescope maker who discovered the planet Uranus in 1781 and infrared solar “heat” rays in 1800. Infrared radiation is commonly employed in auto-refractors for determining the refractive error of the eye including myopia, hyperopia, astigmatism, and higher-order aberrations.

The advantage of using infrared lies in the facility to use electronic sensor-detectable safe levels of radiation almost invisible to the human eye. Further, infrared imaging of biological organs aids in medical diagnostics (thermography), and infrared spectroscopy is used for biochemical investigations. William Herschell pioneered the study of binary stars and nebulae and established the basic form of our Milky Way Galaxy. He was assisted by his sister Caroline, and his work was continued after him by his son, John F. W. Herschell.  
 
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Jean Baptiste Joseph Fourier 1768-1830 CE: Born in Bourgogne, Fourier’s education was interrupted during the French revolution and he decided to accompany Napoleon on his Egyptian campaign. Based on his formulations of heat flow in metallic objects (1807), Fourier proposed that any mathematical function can be represented by trigonometric series.

In the 21st Century, Fourier analysis forms the basis for calculations on the harmonic components of natural images and time series data by vision scientists. Further, Fourier synthesis helps create specific targets for visual psychophysics and neurophysiology research. Modulation transfer in the eye and in any optical system can be quantitatively described by a double integral function of a trigonometric “Fourier” series. Fourier’s work laid the foundation for dimensional analysis and linear programming. He also studied probability and statistics. 
 
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Johann Wilhelm Ritter 1776-1810 CE: Born in Samnitz, Silesia (then in Prussia, now Poland), Ritter was the German physicist who studied medicine at Jena and discovered ultra-violet radiation. He also performed early research on electrolytic cells. Ritter noted Hershell’s discovery in 1800 of “heat-rays” and was inspired to look for “cool-rays” at the other end of the visible spectrum. Ritter noticed that silver chloride was transformed faster from white to black when it was placed at the dark violet-end of the solar spectrum. He termed these "chemical rays," later renamed ultraviolet radiation, used for biochemical skin tests (e.g. carotenoid estimation), fluorescence, and other applications.  
 
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David Brewster 1781-1868 CE: Born in Jedburgh, Scotland, Brewster made discoveries on diffraction and polarization of light and documented in 1815 that the polarization of a beam of reflected light is maximized when the reflected and refracted rays are orthogonal to each other. Further, the tangent of the angle of polarization is numerically equal to the refractive index of the reflecting medium when polarization is maximized.

Brewster invented the kaleidoscope in 1816 and was knighted in 1831. His famous words from an 1830 publication (Quarterly Review) include, “Science flatters no courtier, mingles in no political strife.” Many retinal imaging devices utilize polarization of light as a basis for their filtering and contrast-enhancement technologies. In the eye, the cornea and the retinal nerve-fibre layers are known to alter the polarization of incident light.  
 
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Augustin Jean Fresnel 1788-1827 CE: This physicist and civil engineer, born in Broglie, Normandy, and educated in Paris, refined the theory of polarized light by proving in 1821 that light is a transverse wave.

He developed a system of large concentric rings of triangular cross-section that operated like a giant lens to produce a bright collimated beam from a lighthouse to direct ships in the night.

Fresnel prisms and Fresnel lenses are currently widely employed in optometric eye-care for patients with strabismus, and the concept has been used in the design of intraocular lenses surgically implanted after the removal of a cataractous biological lens from the eye.

Several brands of contact lens also employ such prismatic “echelons” for selective focusing of near objects through the centre of the pupil.

The most recent laser techniques in the 21st Century for the surgical correction of presbyopia (refractive surgery to help focus near objects on the retina), rely on Fresnel echelons etched into the cornea by a femtosecond laser suite. 
  history of optics ben vision research   history of optics ben vision research
         
George Biddell Airy 1801-1892 CE: Born in Northumberland, Sir Airy studied mathematics at Cambridge where he became professor of astronomy in 1828.

He installed a telescope In Greenwich, England and measured Greenwich Mean Time (made legal in 1880) by mapping the transit of stars across the meridian.

By 1847 Sir Airy had devised an instrument for calculating altitude and azimuth for mapping location in the sky.

Such calculations are essential for mapping space as it projects upon the centres of rotation of the eye, and for specifying location on the retina, the cornea, and in the concave bowl of a perimetry device for measuring visual field. The intensity distribution in the image of a star-like object is known as the “Airy disc”-- “maxima” and “minima” forming a point spread function (PSF).
  history of optics ben vision research   history of optics ben vision research
 
Conclusions
The design of optical instruments is an inter-disciplinary endeavour that has received contributions from many machinists and engineers of the middle ages. In addition, the fields of mathematics and biology meet when light enters the eye and patterns in the image become biochemical reactions in the retina. Here, biochemistry turns into cell biology as neural impulses initiate psychological perception.

To review the history of pre-modern optics in relation to current eye care technology has been my attempt in this paper-- from the right-angled triangle (Pythagoras, c. 580- 500 BC) to the point-spread function (George Biddell Airy, 1801-1892). I hope I have succeeded to an acceptable degree.

Acknowledgements
I thank my mentors, colleagues, students, collaborators, employees, advisors and investors. Illustrations are from online world-wide web resources, and are not known to be IP protected.

References
1. Hutchinson Dictionary of Scientists, 1996: Helicon Publishing Ltd., Oxford, UK; Editors S Jenkins-Jones, S Karmali, T Ballsdon, I von Essen, C Thompson, K Young, A Farkas, J Webb, A Dixon and T Caven.
2. The Physics Book: From the Big Bang to Quantum Resurrection, 250 Milestones in the History of Physics, 2011; Sterling Publishing Company, Inc., New York; Clifford A. Pickover
3. Wikipedia: The Free Encyclopedia. http://en.wikipedia.org
4. The Science of Leonardo. Inside the mind of the great genius of the Renaissance, 2007: Doubleday Broadway Publishing Group, Random House Inc., New York; Fritjof Capra.
5. Benjamin Franklin’s Science, 1996: Harvard University Press, Cambridge, MA; I. Bernard Cohen. Adler’s Physiology of the Eye 8th and 11th Edition, 1985, 2011: Saunders, Elsevier, Inc., New York.
 
 
 
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