. A treatise on the diseases of the eye. tant about thirteen inches in a directline from the centre of the mirror, and about eight inches to the right or leftof a line drawn from the mirror to the chin-rest. The screen (s) should cutoff all direct lamplight from the patient; and the stand (g\ which carries asquare of blue glass, should be interposed between the flame and the mirror,but close to the former, and with the glass at such an angle that it shall notreflect light to the patient. The lens, of eight inches focal length and fourinches diameter, roughly set to the height of the eye by the
. A treatise on the diseases of the eye. tant about thirteen inches in a directline from the centre of the mirror, and about eight inches to the right or leftof a line drawn from the mirror to the chin-rest. The screen (s) should cutoff all direct lamplight from the patient; and the stand (g\ which carries asquare of blue glass, should be interposed between the flame and the mirror,but close to the former, and with the glass at such an angle that it shall notreflect light to the patient. The lens, of eight inches focal length and fourinches diameter, roughly set to the height of the eye by the screw at B, isthen placed about eight inches from the patient, with its long double handle THE FIXED OPHTHALMOSCOPE OF LIEBREICH. 743 (h) turned towards the observer, who first so disposes the mirror and lens asto throw a circle of light about the size of a shilling upon the eye of thepatient, and then seats himself behind the mirror to complete the adjust-ments required for a perfect view of the fundus oculi. Whilst looking Fio-. through the aperture he may impress slight movements upon the mirror,turning it either upon the vertical axis of its stem, or upon the horizontalaxis on which it swings in its gimbal. By means of the handle (h) with itsterminal pillar (p), he may move the lens nearer to or further from thepatient, or across the table in such a manner as to transfer the light evenfrom one eye to the other. By causing the pillar (p) to move in an arc hemay render the plane of the lens oblique, so as to displace reflected images,and, by the fine adjustment governed by the screw (k), he may regulate theheight of the lens with exactness. So complete is the mastery over all partsof the apparatus that a very little practice renders it possible to follow allslight movements of the eye as readily as with a hand ophthalmoscope, whilethe resulting image is about four times as large as any that an ordinaryhand ophthalmoscope will afford. The large mirror and the position o
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Keywords: ., bookcentury1800, booksubjecteye, booksubjecteyediseases, bookyear
