Robert Marcus Gunn (1850–1909)
“The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ but ‘That’s funny …’” – Isaac Asimov
There are many eponyms in ophthalmology but none as varied across the field as Marcus Gunn – from retina and oculoplasty to neuro-ophthalmology. To many, inspiration can hit out of nowhere, but for Gunn, could it have been the influence of his company? He studied under Douglas Argyll Robertson and went on to describe another pupillary sign. He was a contemporary of the novelist Robert Louis Stevenson and perfected the art of ophthalmoscopy by studying the retina of “lunatics” in the Perth District Asylum and found them to be no different from those of “sane population,” contrary to the common belief. He studied comparative anatomy under the aegis of Professor Edward Albert Sharpey-Schäfer and later traveled to Australia to collect study specimens from the eyes of indigenous species, specifically marsupials. He was also one of the scientists involved in the study of zoological specimen collected by the Challenger expedition.
Robert Marcus Gunn was born in Dunnet, Sutherlandshire, in Scotland. He completed his medical education in 1873 in the Universities of St. Andrews and Edinburgh. After a year as a house physician in Moorfields Eye Hospital, London, he traveled to Vienna in 1874, to learn from Eduard Jaeger, Carl Ferdinand Ritter von Arlt, and Karl Stellwag von Carion. In 1876, Gunn returned to Moorfields as a senior house surgeon and introduced whatever knowledge he had acquired, including Lister’s sterile techniques, systematic method of in-patient note taking, instrument care, and nursing regimen. He went on to become the Senior Surgeon at Moorfields, President of the Ophthalmology Section of British Medical Association, and President of the Ophthalmological Society of United Kingdom.
Gunn’s earliest publication was on a peculiar association in patients with congenital ptosis, which came to be known as the ’jaw-winking phenomenon.’ He described this in 1883, in a 15-year-old girl with ptosis of her left eyelid. It was first noticed when the child was 5 weeks old, when her left eyelid “nearly went out of sight” while suckling. A committee was set up to corroborate this, and their report was published along with Gunn’s findings. What is interesting about this report is the examination of the child as a whole and not just the eye or the eyelid. In the original report, there was also an associated lagophthalmos and miosis of the affected eye. They concluded that the levator was supplied by both the nucleus of the third nerve and the portion of the fifth nerve supplying the external pterygoid. They attributed the additional findings of lagophthalmos to incomplete relaxation of levator due to its additional innervation by the fifth nerve and miosis to the increased tone of sphincter from the third nerve nucleus with a normal number of nerve cells, all of which were not supplying the levator accounting for the ptosis. The term Marcus Gunn jaw winking is currently restricted only to the finding of eyelid elevation with contraction of the lateral pterygoid in patients with congenital ptosis. The inverse Marcus Gunn phenomenon bears his name by default. Here, the affected eyelid becomes more ptotic with mouth opening, presumably due to the inhibition of the nerve to levator with contraction of the lateral pterygoid. It is seen in association with acquired central nervous system disease. Marin-Amat syndrome is a clinically indistinguishable condition due to the abnormalities of the facial nerve.
In 1883, he also described “peculiar dots in the retina” and called them “Crick dots” after the family in which he first noticed them. Today, we call the glistening white–yellow tiny dots near the optic disc with no pathological consequence, Gunn’s dots.
His classic paper, “Ophthalmoscopic Evidence of General Arterial Disease” in 1898, recognized retinal arterial sclerosis as a sign of systemic disease. To quote from the same paper, “It will be understood from the title of this paper, that I do not propose to consider alterations in retinal arteries generally. My object is, in the first place, to describe certain ophthalmoscopic changes, – all, I believe, dependent primarily on an affection of retinal arteries; and secondly, to give my reasons for this belief, and for the opinion that such visible primary changes in retinal arteries are very commonly, if not constantly, a part of a similar, more general, and therefore more important change in small arteries elsewhere. The arteries have an exceptionally bright reflex; the central light-streak is very distinct and sharp, while the whole surface of the vessel is of a somewhat lighter colour than usual. This condition has been observed in many cases of chronic albuminuria, and in several cases where no albumen was found, but where high arterial tension suggested the probability of changes in the arteries similar to those usually associated with chronic renal changes. The ophthalmoscopic appearance is presumably due to hyaline degeneration of the arterial walls. Attention is also directed to the effect produced on the veins by arteries overlying them. Where an artery, even a small twig, passes over a retinal vein, the circulation in the latter is much impeded. In some cases the vein is indistinguishable just at the spot where it is crossed, and is evidently distended for some distance peripherally from this point.” The Marcus Gunn crossing sign is a well-recognized feature of essential hypertension.
In 1902, hidden within the lines of a detailed paper on differentiating functional vision loss from a hysterical one, was one of the most important signs in ophthalmology, the relative afferent pupillary defect (RAPD), also known as the Marcus Gunn pupil. “It is not sufficient to find that it [the pupil] contracts well or fairly well on exposure; the eye must also be kept under direct stimulation of light and the pupil watched as to whether or not it shows that secondary dilatation under continued exposure that is found associated with the amblyopia of retro-ocular neuritis. If the vision of one eye only is affected, it is important to compare the behaviour of the two pupils when stimulated directly or consensually. Thus, in partial affection of the right optic nerve the right pupil will show this secondary dilatation during continued exposure to direct stimulation, while the left pupil will show the same behaviour on consensual stimulation. On the other hand, on stimulation of the left eye both the right and left pupil will behave normally. I need not remind you of the importance of this observation, in as much as it not infrequently enables us to diagnose a retro-ocular neuritis in the absence of all ophthalmoscopic evidence.” The swinging flashlight test for detecting RAPD was described much later by Levatin in 1959 who referred to the condition as “dynamic anisocoria.” This term is somewhat misleading because there is actually no anisocoria at any point of time during the test!
Gunn was amongst the first to insist on studying fine changes of the anterior segment, the cornea, and iris using the strongest available simple microscope. It is said that he introduced the high-powered pocket magnifier, what is commonly used in Moorfields.
As a surgeon, he felt responsible for his patients and rarely allowed anyone else to operate on them. A skilled clinical observer, he was a famed, self-taught ophthalmoscopist and his course on the use of the instrument and interpretation of findings were highly sought after. From his childhood, he had an interest in botany, marine biology, and zoology, and he had an extensive collection of Jurassic fossils from the Old Red Sandstone systems in Scotland. Many of these are housed in the British Museum.
“He was endowed with marked intellectual gifts, and was an exceedingly keen and accurate observer; his mental grasp prompt, clear, and strong; his judgement careful and well balanced, whilst his matter-of-fact simplicity was qualified by a ready sense of humour. Fond of reading, and having a good memory, he had the gift of rapidly extracting and retaining what he wanted from a book. Gunn’s reputation in the ophthalmic world is so well established that any testimony thereupon would be superfluous. He was universally recognized as one of the most able and experienced of ophthalmologists, and his opinion was very highly valued by his professional brethren.” What more can anybody add?
He died an untimely death on November 29, 1909, from painful and distressing bouts of influenza.
“It is not likely that posterity will fall in love with us, but not impossible that it may respect or sympathize; so a man would rather leave behind him the portrait of his spirit than a portrait of his face.” – Robert Louis Stevenson
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1. Roper-Hall G. Historical vignette:Robert Marcus Gunn (1850–1909):Scottish ophthalmologist, skilled observer, and gifted teacher Am Orthopt J. 2015;65:121–7
2. Nezhad GS, Jalalpour MH, Dalfardi B. Robert Marcus Gunn (1850–1909) J Neurol. 2015;262:2599–600
3. Gunn RM. Congenital ptosis with peculiar associated movements of the affected lid Trans Ophthalmol Soc UK. 1883;3:283–7
4. Thompson HS. The vitality of the pupil:A history of the clinical use of the pupil as an indicator of visual potential J Neuroophthalmol. 2003;23:213–24
5. Gunn M. Ophthalmoscopic evidence of general arterial disease Trans Ophthalmol Soc UK. 1898;18:356–81
6. Gunn RM. Functional or hysterical amblyopia Ophthalmol Rev. 1902;21:271–80
7. Levatin P. Pupillary escape in disease of the retina or optic nerve AMA Archives of Ophthalmology. 1959;62:768–79
8. . Robert Marcus Gunn, M.A., M.B.Edin., F.R.C.S.Eng Br Med J . 1909;2:1719–21
9. Pearce J. The Marcus Gunn pupil J Neurol Neurosurg Psychiatry. 1996;61:520