The ophthalmoscope : its varieties and its use / translated from the German of Adolf Zander by Robert Brudenell Carter ; with notes and additions by the translator.

Date:: 1864

Credit: The ophthalmoscope : its varieties and its use / translated from the German of Adolf Zander by Robert Brudenell Carter ; with notes and additions by the translator. 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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$B in c and d. Rendered still more convergent by the dioptric apparatus of B, they intersect at some point in front of the retina, for example, at a, and form on the retina the dispersion circle a j3. As shown in Fig. 6, on account of the passive state of accommodation of the eye, the rays proceeding from it will follow courses parallel to the lines of direction o x and j3 ccf and after their refraction by the lens L will unite to form at a j3' an actual inverted image of a /3. While the great advantages of this instrument in respect of the brightness, sharpness, and beauty of its images strongly recommend it for clinical demonstrations, where the head of the patient can be supported by an assistant, yet the fact that it is somewhat difficult to manage diminishes its practical utility for ordinary purposes. 6. THE SMALLER OPHTHALMOSCOPE OP RTTETE. To obviate this inconvenience, Ruete has constructed a smaller, portable instrument, of which the following is a description :— A small, centrally-perforated concave mirror (of 1J diameter, and 4—6 focal length) is attached by a hinge-joint to a brass staff, like, but larger than, that of Coccius's ophthalmoscope. Behind the mirror is a spring clip to contain ocular lenses. Immediately below the hinge the staff carries a longer rod, divided into six or eight joints, sliding backwards and forwards one upon another. At the farther end of this is a spring ring to carry concave or convex lenses—the whole corresponding to the arm h, Fig. 8. Above the handle is a cross-bar, like that of the arm d, Fig. 29, which carries a pasteboard screen on a short stem. This instru- ment gives very good images; but in consequence of the length of the handle and arms, its management and its application to the eye of the patient are sometimes difficult. 7. THE OPHTHALMOSCOPE OP ANAGNOSTAKIS. This instrument consists of a small, round, concave mirror, 5 centi- metres in diameter, having a focal length of 4J. Its silvered surface is protected by a blackened plate of copper. The centre of the mirror is perforated, the opening having a diameter of 4 millimetres. For con- venience in use, the mirror is attached to a short handle. The manner of using is the same as for other ophthalmoscopes. 8. THE OPHTHALMOSCOPE OF ULRICH is shown in Fig. 11 in perspective, in Fig. 12 in section. It consists of two tubes, blackened within, and united at an angle of about 40°; one of them, a b, inclosing the mirror and lenses, the other admitting the light to the first. The length of the first tube, which Ulrich calls the$