Early contact glasses

The timeline of contact lenses begins with a false dawn in the early modern period but gathers pace from the early 19th century...

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Leonardo da Vinci, 1508

There is a traditional claim, much repeated in optometry and ophthalmology text books (and more latterly on websites, many copying from each other), that Leonardo da Vinci described and illustrated contact lenses in 1508, thereby giving birth to the study of their theoretical priniciple if not, at this stage, their practical application. The latest scholarship, particularly the work of Professor Robert Heitz of Strasbourg (2003), demonstrates how this myth is of relatively recent origin (from the late 1950s) and how it has been distorted and extended by subsequent authors who haven’t gone back to the original sources. Heitz concludes that of the three relevant sources, two in fact illustrate something quite different, but that the third source (ironically the one least often cited) can be interpreted as alluding unintentionally to a principle that others would later develop, even if Leonardo certainly did not.

Nothing in Leonardo’s notes relates to the use of contact lenses for optical correction but even in the 1880s when the modern history of contact lenses (in a practical, not just a theoretical sense) had indisputedly begun, the first contact shells were cosmetic in purpose and nothing to do with optical correction either, so that's not necessarily a problem. We do know that Leonardo was interested in the dioptrics of refraction in liquids and lenses as well as the catadioptrics of reflections in spherical mirrors. This rightfully entitles him to a place in the history of ophthalmic optics.

Leonardo da vinci sketch circa 1508

At some point before his death (1516) but certainly in one of his later works investigating dioptrics and catadioptrics in the tradition of the eastern scholar Alhazen and the Medieval English monk Roger Bacon (which Leonardo began no earlier than 1505) he described and illustrated a potential experiment (almost certainly never performed) in which a man immerses his face in a spherical glass bowl of water and is able to see his own shoulders. The illustration to the right is taken from that work. The point of this experiment was to demonstrate that a transparent convex surface filled with water allowed rays of light from the peripheral visual field to focus on the pupil after refraction, as they passed through two media of different refractive index.
From a close analysis of his notes, some of which appear to have been amended, possibly years after first being written, Leonardo seems to have realised that the surface of what he called ‘the luce of the eye’ has been transferred, so-to-speak, to the edge of the bowl through the action of the water contained in the bowl which is in direct physical contact with both eyes and had effectively neutralised the refractive power of the eye surface itself. In other words this would be a completely impractical bioptic contact lens. It is doubtful however that the unit could have been hermetically sealed as required and the participant in the experiment would have been at risk of drowning because it covered the whole face. In the other relevant sources Leonardo does describe smaller liquid-filled bowls for monocular use over or in front of just the eye itself, but the point of those experiments is even further removed from our subject and more in the realm of the history of optical physics than in the history of medical devices.
We can note that the experiment described above has parallels with the early contact lenses of the late 19th and early 20th centuries, that were very large and needed fluid as a lubricant and that when calculating the optical power of lenses to be ground the practitioner had to take into account the refractive index of the liquid and it was the combined power of lens and liquid that provided the optical correction.

Nevertheless, whatever Leonardo did or did not come up with, no one developed the idea any further until...

Rene Descartes, 1637

Rene Descartes portrait engraving

It is often claimed that in 1637 the scientist and philosopher Rene Descartes suggested the concept of corneal lenses. The reference comes in the seventh discourse of  his essay La Dioptrique. This discourse was entitled Des Moyens de Perfectionner La Vision (On Means of Perfecting Vision) in which he suggests, theoretically, that enlargement of the retinal image may be achieved by lengthening the ocular globe. Already we can assert that modern contact lenses do not work by increasing the axial length and are not concerned with enlarging an image, merely with correcting a refractive error....and the experiment described in the discourse relates to a normal (emmetropic) eye, not one with an error.

Descartes tube

In this discourse Descartes described and illustrated an extending water-filled tube which would serve the purpose of lengthening the eye's axis. The tube was open at the viewer's end, allowing the water to come into direct contact with the eye. The other end of the tube was to be made of glass of the same curvature as the cornea of the eye, but in his text Descartes made it clear that this cover was not a lens and that since there was no effective means of measuring the curvature of the cornea, it would be impractical to produce such a cover. If it had been possible it would have created effectively a new surface of refraction at some distance from the eye. In this we certainly seem to be encountering the concept of corneal neutralisation. The length of the tube was adjustable so the device, if it had ever been made, would have had some historical parallel with the telescope but not so much with contact lenses since it was an afocal device and was not worn under the eyelids but had to be held in place by constant external pressure. Indeed, Descartes wrote that placing the water right in front of the eye would also be impractical which is why he went straight on to describe a glass tube closed at both ends - in effect describing the principle of the Galilean telescope. As with all Cartesian reasoning he was outlining a series of steps towards solving a problem. The water-filled tube in direct contact with the eye was only the first and most readily dismissed step in his argument. Thus we can conclude that it was never put forward as a serious practical suggestion and that the allusion to corneal neutralisation was incidental at best.

Did you know?

A member of the British Optical Association, J. R. Levene FBOA attempted unsuccessfully to recreate Descartes' tube in 1977. Levene was perhaps the first modern scholar to challenge the idea that this was a contact lens, crucially identifying that many of the illustrations reproduced from the Discourse failed to show that it was a telescopic (extending) device.

The illustration shows Descartes' water-filled tube as illustrated in the 3rd edition of La Dioptrique (1668) in our historical books collection. The three-part nature of the tube is readily apparent.

It was then another century and a half before...

Thomas Young, 1801

Thomas Young

In 1801 Thomas Young (1773-1829) fitted a lens to a cornea with a surrounding wax collar to retain fluid behind the lens, neutralising it and thus showing that the cornea was not involved in accommodation.

Young was one of those admirable if annoying polymaths who excelled in several fields. If only he had concentrated upon the corneal lens idea he might have invented contact lenses far sooner than they were. Both a physician and a physicist he embodied the unique link between ophthalmologists and optometrists to be detected subsequently in this branch of optics. The year before he had moved into his late uncle's house in London and thus had the time and space to devote to his studies.

Three of the other subjects he investigated would find applications in twentieth century contact lens materials: The size of molecules, the surface tension in liquids and the elasticity of materials (which is still defined by Young's modulus).  

Thomas Young Lectures front page

I take, out of a small botanical microscope, a double convex lens, of eight tenths radius and focal distance, fixed in a socket one fifth of an inch in depth; securing its edges with wax, I drop into the socket a little water, nearly cold, till three-fourths full, and then apply it to my eye, so that the cornea enters half way into it, and it is every where in contact with the water. My eye immediately becomes presbyopic, and the refractive power of the lens, which is reduced by water to a focal length of about 16 tenths, is not sufficient to supply the place of the cornea, rendered inefficacious by the intervention of the water; but the addition of another lens, of five inches and a half focus, restores my eye to its natural state, and somewhat more.

(From: A Course of Lectures on Natural Philosopy and the Mechanical Arts, published in two volumes, 1807. Available for study in the College Library).

Thomas Young neutralising the cornea with a lens

Young discovered both that the cause of astigmatism and the fact that the cornea was not involved in accommodation. This diagram, when orientated the right way, shows Young's neutralising corneal lens mounted in a brass rim. It had to be used in this position to prevent the liquid from spilling.

Franz Resisinger, 1824

In Germany in 1824 Franz Reisinger (1787-1855) mentioned the technique of corneal grafting suggesting its potential application from animal donor to human recipient. He also coined the term 'Keratoplasty' but the surgical solution was to be delayed for the time being.

John Herschel, 1827

John Herschel

In 1827 John (later Sir John) Herschel (1792-1871) suggested grinding a lens that conformed to the surface shape of the eye.

Sir John, pictured here in old age, researched corneal irregularities and astigmatism, realising that neutralisation of the cornea in such cases could lead to an improvement in vision. He actually suggested making moulds of the eye with transparent animal jelly but we do not know if he ever tried to produce such a mould. Some early twentieth century historic articles refer to his gelatine moulds - but this could just be careless paraphrasing of the source material.

Should any very bad cases of irregular cornea be found, it is worthy of consideration whether at least a temporary distinct vision could not be procured, by applying in contact with the surface of the eye some transparent animal jelly contained in a spherical capsule of glass; or whether an actual mould of the cornea might not be taken and impressed on some transparent medium.     

(From: Light (1827) republished as Section XII 'Of the structures of the eye and vision' in the Encyclopaedia Metropolitana, 1845).

As Arthur Bennett wrote in his Optics of Contact Lenses (1949) it would appear that Herschel's idea was conceived directly from Airy's work on astigmatism using sphero-cylindrical spectacle lenses. Herschel evidently preferred a more direct form of correction and described his idea for a contact glass as the 'strict method'. The animal jelly would literally build up the surface of the cornea and the glass shell would be the means of retaining it in position.

Did you know?

The International Society of Contact Lens Specialists (ISCLS) was founded by three optometrists in 1954. The ISCLS has awarded the Herschel Medal since 1957 for outstanding services to contact lenses. The 2005 recipient was Donald Ezekiel, an optometrist from Perth, Australia and the 2008 recipient was Dr William J. Benjamin, tenured Professor of Optometry and Vision Science at the University of Alabama at Birmingham, School of Optometry (UABSO). The College is delighted that one of its own Fellows, Frank Petticrew FCOptom DCLP, an optometrist from Belfast, was awarded the Herschel Medal in December 2012.