Sir John Herschel Sir John Herschel

Sir John Frederick William Herschel, first Baronet, was the only son of distinguished astronomer Sir William Herschel. John Herschel was a mathematician as well as an astronomer, was the first to take a photograph onto glass and gave us the terms, ‘photography’, ‘negative’, ‘positive’, and snapshot’. His researches extended into corneal irregularities and astigmatism and he realised that in these cases vision could be improved by neutralising the cornea. Herschel suggested the making of moulds of the eye with gelatine although there is no evidence that this was actually done. He included these observations in his article on ‘Light’ in 1827 and in the Encyclopaedia Metropolitana in 1845.

“Malformations of the cornea are much more common than is generally supposed, and few eyes are, in fact free from them… A remarkable and instructive instance of this kind has recently been adduced by Mr G. B. Airy, in the case of one of his own eyes; ….. which, from certain defects in the figure of its lenses, he ascertained to refract the rays to a nearer focus in a vertical than in a horizontal plane so as to render the eye utterly useless. This, it is obvious, would take place if the cornea, instead of being a surface of revolution (in which case the curvature of all its sections through the axis must be equal), were of some other form, in which the curvature in a vertical plane is greater than in the horizontal. It is obvious that the correction of such a defect could never be accomplished by the use of spherical lenses. The strict method, applicable in all such cases, would be to adapt a lens to the eye, of nearly the same refractive power, and having its surface next to the eye an exact intaglio facsimile of the irregular cornea, while the external should be spherical of the same general convexity of the cornea itself; for it is clear that all the distortions of the rays at the posterior surface of such a lens would be exactly counteracted by the equal and opposite distortion of the cornea itself.”

Herschel then added the all important footnote:

“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. The operation would of course be delicate, but certainly less so than that of cutting open a living eye, and taking out its contents.”

The Herschel Medal has been awarded by the International Society of Contact Lens Specialists (ISCLS) since 1957 for outstanding services to contact lenses.

Light London 1827; republished as Section XII ‘Of the structures of the eye and of vision’, Encyclopaedia Metropolitana, 4 396-404, London 1845.