File:A treatise on the diseases of the eye (1883) (14784454245).jpg

Identifier: treatiseondiseaseso00well (find matches)
Title: A treatise on the diseases of the eye
Year: 1883 (1880s)
Authors: Wells, J. Soelberg (John Soelberg), d. 1879 Bull, Charles Stedman, 1844-1912
Subjects: Eye Eye Diseases
Publisher: Philadelphia, C. Lea's son & co.
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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ion at his command. The second cylinder con-tains the concaves of moderate focal power, and the third is composed of thehigh numbers, both positive and negative. These strong numbers aredesigned for the determination of the highest degrees of errors of refractionand for the measurement of the inequalities of the fundus, such as excava-tions and elevations of the optic nerve, projections of tumors, retinal detach-ments, membranes in the vitreous, etc. The mirror, being contained in a separate case, is made detachable fromthe rest of the instrument, which can then be used as an optometer, thepatient himself revolving the cylinder till the suitable glass is obtained. Besides the common concave mirror, Dr. Loring has had another con-structed, which was originally designed for a stenopseic slit to be used withthe instrument when employed as an optometer for the determination of 1 Amer. Journal of Med. Sci., April, 1870, p. 340. 736 THE USE OF THE OPHTHALMOSCOPE. Fis. 233. I,^. J. Fii/. ti.
Text Appearing After Image:
Fig. 1. Back of Lorings ophthalmoscope with cylinder in position. Fig. 2. Front view ofinstrument. Figs. 3 and 4. Remaining cylinders detached. Fig. 5. Astigmatic optometerand mirror. astigmatism. It consisted of a thin plate with a slit in it, whose length wasequal to the diameter of the perforations in the cylinder. This was mounted THE PORTABLE OR HAND OPHTHALMOSCOPES. 737 like the mirror, and made to fit in the mirror cell in which it revolved, so asto allow the slit to correspond with any given meridian of the cornea. Themeridian once determined, the patient turned the cylinder till the suitableglass was obtained. This plate was subsequently made with a polished sur-face in front, and then was made to serve also as a mirror for determining,by means of the ophthalmoscope, the amount of astigmatism in the principalmeridians of the eye.—H.) (The modification of the Rekoss system adopted by Knapp consists of twoundetachable, revolving disks, one containing concave and the other con

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