Why was Leonhard Euler blind?

Abstract

Leonhard Euler was one of the most eminent mathematicians of all time. In 1735, he developed right periocular swelling, partial loss of vision, and the onset of lifelong recurrent fevers from a heretofore-unknown affliction. Three years later, he developed an infection in the right eye area resulting in right eye blindness, a drooping right upper eyelid with a smaller right pupil, and a right vertical eye muscle imbalance. In 1771, complications from a left cataract operation rendered him almost totally blind now in both eyes. On 18 September 1783, Euler lost the remaining vision in his left eye, and later that day died suddenly from a presumed brain haemorrhage. For centuries, an essential part of the Russian diet had been raw milk, the consumption of which is a significant risk factor for brucellosis (undulant fever) which was endemic in Russia in the eighteenth century (and still is today). Given the history of an acute recurrent infectious febrile illness with ophthalmic and neurological complications and having the probable terminal event being a haemorrhagic stroke, Euler’s most likely posthumous diagnoses are ocular, systemic, and neuro-brucellosis with a cerebral haemorrhage from a ruptured Brucella-infected aneurysm.

Acknowledgements

The authors gratefully acknowledge the critical reviews of the manuscript by: (1) Donal O’Shea, PhD, Emeritus President and Professor of Mathematics, New College of Florida, Sarasota, FL; (2) Mark Sheingorn, PhD, Professor Emeritus, Department of Mathematics, CUNY, New York, NY; (3) Neil R. Blacklow, MD, Professor Emeritus (Infectious Diseases), University of Massachusetts Medical School, Worcester, MA.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Notes

1 See for instance ‘The Story of Mathematics: “Leonhard Euler – Swiss mathematician”’: https://www.storyofmathematics.com/18th_euler.html. Accessed 20 July 2021.

2 ‘Reading Feynman: “Euler’s formula”’: https://readingfeynman.org/2013/10/26/eulers-formula/. Accessed 3 April 2022.

3 https://www.popularmechanics.com/space/solar-system/a38986125/trojan-asteroid-shares-earth-orbit/ Accessed 3 April 2022.

4 https://mathworld.wolfram.com/EulerCurvatureFormula.html. Accessed 3 April 2022.

5 ‘Project Euler: “Su Doku”’: https://projecteuler.net/problem=96. Accessed 10 June 2021.

6 ‘Venn diagrams vs. Euler diagrams’: https://creately.com/blog/diagrams/venn-diagrams-vs-euler-diagrams/ Accessed 10 June 2021.

7 Except where otherwise stated, this biographical summary is based on (Calinger 2016).

8 ‘MacTutor: “Eulogy of Leonhard Euler by Nicholas Fuss”’: https://mathshistory.st-andrews.ac.uk/Extras/Euler_Fuss_Eulogy/. Accessed 22 June 2021.

9 M de Condercet, ‘Eulogy to Mr Euler’: http://eulerarchive.maa.org/historica/condorcet.html. Accessed 22 June 2021.

10 ‘St Petersburg Essential Guide: “Russian cuisine”’: https://www.st-petersburg-essentialguide.com/russian-cuisine.html. Accessed 22 June 2021.

11 Horner Syndrome is caused by a disruption of the sympathetic nerve pathway from the brain to the eye on one side of the body, resulting in a smaller pupil size and a drooping of the eyelid, ipsilaterally.

12 The fourth cranial nerve (CN IV) innervates the eye’s superior oblique muscle. A paralysis of this muscle causes the eye to become elevated (compared to the normal opposite eye) resulting in ‘scleral show’ (see Figure 4).

13 ‘Scleral show’: the white part of the eye (the sclera) shows between the inferior border of the iris and the edge of the lower eyelid, indicating that the involved eye is elevated (hypertropic) compared to the opposite eye.

14 ‘Oculist’ is actually a rather out-dated and old-fashioned term for an ophthalmologist. However, in former times, many oculists were self-taught, itinerant quacks while, today, ophthalmologists are physicians with four years of medical school who have completed an internship, a three (or four) year highly competitive residency, frequently followed by a 1–2 year fellowship in a sub-specialty area. Others have a masters degree or PhD in an area of science, Master of Public Health or Master of Business Administration degree, or are Board Certified in another area of medicine, most frequently pediatrics or internal medicine.

15 Eclipse blindness is characterized by central, not total, vision loss due to a burn of the foveal-macular area of the retina, the very centre and most important portion of the eye. (The fovea is the portion of the retina having the best visual acuity due to the very high concentration of cone cells.) With a foveal-macular burn, the peripheral retina remains intact. This type of visual loss is not associated with a Horner Syndrome or CN IV palsy.

16 Even though compounds of arsenic (used by the Greco-Roman civilization) and mercury (used since the sixteenth century) had been employed for infections well before Euler’s lifetime, there is no evidence of his being treated with any therapeutic agent.

17 Edward Jenner was a country doctor living in Berkeley (Gloucestershire), England, who, in 1796, performed the western world’s first vaccination. Taking pus from a cowpox lesion on the hand of a milkmaid named Sarah Nelmes, Jenner inoculated an eight-year-old boy, James Phipps. Six weeks later Jenner applied actual smallpox material to two sites on Phipps’s arm; the boy was unaffected by this maneuver. Jenner is now considered to be ‘the father of immunology’.

18 https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section8.html. Accessed 5 March 2022.

19 American Academy of Ophthalmology; D Turbert, ‘What is histoplasmosis?’: https://www.aao.org/eye-health/diseases/what-is-histoplasmosis. Accessed 10 June 2021.

20 See also https://a2zhealthy.com/brucellosis. Accessed 5 March 2022.

21 Formulated by Robert Koch (1843–1910) and published by him in 1890. (1) Organisms were recovered by Bruce from the spleens of infected soldiers at autopsy. (2) These isolated organisms were grown in pure culture and injected into seven healthy monkeys. (3) Four of these monkeys died and three developed fevers characteristic of brucellosis. And, (4) identical organisms were re-isolated from the tissues of the deceased and diseased monkeys.

22 https://www.cdc.gov/brucellosis/pdf/brucellosi-reference-guide.pdf. Accessed 5 March 2022.

23 https://www.foodnavigator.com/Article/2012/10/31/Brucellosis-spreads-through-Russia#:~:text=Mediterranean%20fever%20(brucellosis)%20is%20spreading,over%20the%20last%20three%20months. Accessed 13 June 2021. http://outbreaknewstoday.com/russia-brucella-outbreak-affecting-humans-animals-reported-voronezh-region-94484. Accessed 5 March 2022.