Babbage and Defective Vision

This is the first in a set of blog posts by Plan 28's Technical Director, Doron Swade, about Charles Babbage's many inventions.

Babbage and Defective Vision

In 1847 Babbage constructed a prototype ophthalmoscope – a device for examining the inside of the eye. The device was rejected by a leading eye specialist, Wharton-Jones, and four years later the invention was credited to Helmholtz. 

In the 1820s he conducted an elaborate experiment to find the least fatiguing combination of ink and paper for reading printed mathematical tables. He printed the same two sample sheets of his own logarithm tables using every combination of colour and hue of ink and paper available in London – a total of thirteen different inks on 151 different colours of paper including black ink on black paper and green ink on green paper.  The results were bound in 21 volumes in 1831.

It has always been a puzzle as to why Babbage went to such lengths to explore the ergonomics of reading tables, and why he was drawn to investigating the inner eye. It is easy to see his preoccupations with colour combinations as part of his notorious oddity and his attempts at an ophthalmoscope as simply a product of exuberant invention.

Richard Keeler, an historian of ophthalmology, has found conclusive evidence that Babbage suffered from a vision impairment – bilateral monocular diplopia – a condition in which there are two foci in the same eye, resulting in double vision when looking through either eye singly. At risk of medicalising historical cause, Babbage’s vision impairment provides a persuasive alternative to eccentricity to which he was anyway disposed – the search for improved legibility in the case of colour permutations, and attempts at self-diagnosis in the case of the ophthalmoscope. 

A modern reconstruction of Babbage's ophthalmoscope: