On an improved optometer for estimating the degree of astigmatism and other errors of refraction / by John Tweedy.

Licence: Public Domain Mark

Credit: On an improved optometer for estimating the degree of astigmatism and other errors of refraction / by John Tweedy. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.