. The principles and practice of surgery. ibuted theophthalmoscope ; yet already a great number of modifications have beensuggested, among which may be enumerated the portable hand ophthal-moscopes of Liebreich, Coccius, Zehen-der; the stationary ophthalmoscopes ofLoring, Liebreich, Smith, Beck; thebinoculars of Giraud, Teulon, Laurence,Heisch ; and the auto-ophthalmoscope,with which, by an ingenious arrange-ment of lenses, the operator is able toexamine his own eyes. Of all these various forms of ophthal-moscopes, the portable apparatus ofLiebreich is in most general use; butthe instrument de
. The principles and practice of surgery. ibuted theophthalmoscope ; yet already a great number of modifications have beensuggested, among which may be enumerated the portable hand ophthal-moscopes of Liebreich, Coccius, Zehen-der; the stationary ophthalmoscopes ofLoring, Liebreich, Smith, Beck; thebinoculars of Giraud, Teulon, Laurence,Heisch ; and the auto-ophthalmoscope,with which, by an ingenious arrange-ment of lenses, the operator is able toexamine his own eyes. Of all these various forms of ophthal-moscopes, the portable apparatus ofLiebreich is in most general use; butthe instrument devised by Loring, ofthis city, is generally preferred byAmerican ophthalmologists. Liebreichs instrument consists of aconcave metal mirror, one inch and a half in diameter, with a focallength of six inches, and a central aperture of one tenth of an inch indiameter. The reflector is supported by a light handle, and has attachedto its margin a movable socket, intended to receive, as occasion mayrequire, a convex or a concave lens. Fig. Liebreichs Ophthalmoscope. THE OPHTHALMOSCOPE. 577 Fig. 301. The direct method of using this instrument is as follows. The roombeing darkened, the patient is seated beside, and a little in front of, asteady and clear artificial light, while the surgeon places himself directlyopposite, and, with hisright eye at the apertureof the reflector, directsthe light upon the eye ofthe patient. The retinamay now be seen, givingto the pupil an orange-red color ; and by gradu-ally approaching the mir-ror to the eye, the differ-ent portions of the retinalstructure may soon beclearly recognized. The indirect methoddiffers from the direct,only in the use of an ob-ject glass, as representedin the accompanyingwood-cut. (Fig. 302.) The supplemental concave and convex glasses, intended for theclip attached to the frame of the mirror, are to be used in case the Fig. 303.
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