The refraction of the eye : including a complete treatise on opthalmometry : a clinical text-book for students and practitioners / by A. Edward Davis.

Date:
1900
Catalogue details

Licence: In copyright

Credit: The refraction of the eye : including a complete treatise on opthalmometry : a clinical text-book for students and practitioners / by A. Edward Davis. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    by the dotted line in Fig. 7, and b b', the distance between the inner edges of the images of the graduated mire, each repre- sents the amount of deviation caused by the prism, which is 2.95 mm. Now as a a' is the image of the object under meas- B Fi(}. 7. — A, diagram of the mires alone, li, reflection of the whole instrument from the front of the cornea, with the arc at 180°. urement, that is, the distance between the inner edges of the two mires, we know its size to be just 2.95 mm. in this instance. Take a case in actual practice. For example, when the instrument is focussed properly on an eye, the black lines dividing the mires become coincident with each other in the