A new model of a small ophthalmoscope / by Walter L. Pyle.

  • Pyle, Walter L. (Walter Lytle), 1871-1921.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A new model of a small ophthalmoscope / by Walter L. Pyle. 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.

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    Red concave. Aperture (white). v ' 0 3 4 5 White convex. G G 0 Aperture (red). When the lower driving-wheel which moves this disc is turned to the right, it brings the convex lenses successively before the sight-hole. When the -f- 6 D. lens is in this po- sition, another turn brings the red aperture before the eye. The observer at once notices the change in focus, and his finger is raised and the inner disc is revolved directly by its milled edge, as in the Loring instrument. The lenses on the inner disc are so arranged that the first turn to the right brings before the sight-hole a + 8 D. lens, and so on up to 24 D., without removing the instrument from its first posi- tion before the eye. Similar rotation to the left causes the concave lenses from 1 I), to 24 D. to appear successively be- fore the sight-hole. The inner disc of lenses, that is the one nearest to the observer’s eye, is arranged thus: Aperture. 0 8 8 10 10 White I12 12 ] l Red convex. ! 14 r concave. 10 10 14 J White. 24 Red. 24 20