752 OPEEATIOKS rPOK THE EYE AND EAR. 



penetrated between the ciliary processes and the border of the 

 lens, and presently becomes visible to the operator, passing be- 

 yond the internal border of the pupil. By a sHght motion up- 

 ward and downward, the capsule is then opened and the lens 

 depressed, first backward, then yertically, and pushed downwai-d 

 into the lower part of the yitreous humor. A gentle rotation of 

 the instrument then releases it from the substance of the lens, and 

 it is returned to its horizontal position. The instrument is not 

 withdrawn until it is ascertained that the lens is estabHshed in its 

 new position. 



"When the puncture is made through the cornea the entrance 

 into the eye takes place near the center of this membrane, and 

 the access to the lens takes place through the opening of the 

 pupil. 



In either case the wound of the globe is insignificant. 



2d. Method. Extraction. — There are two principal modes of 

 Ci^eration, one by extraction through a tiap of the cornea upward, 

 and another by a linear incision on the side of the globe. 



In the operation by the fiap iqncard, the knife of Eichter, 

 modified by Beer (Fig. 545), is introduced horizontally through 



Fig. 545.-Knife of Beers. 



the cornea, near the sclerotic border, a little aboye the horizontal 

 diameter of the globe, with the edge turned upward, and as soon 

 as the point of the instrument has entered the anterior chamber 

 of the eye, it is pushed in a straight, horizontal direction, passing 

 into the anterior chamber (Fig. 546), and when its point reaches 

 the opposite side of the cornea, it is pushed through it in such 

 a manner that its exit and its entrance occur at equal distances 

 from the sclerotic border. 



The flap is comjDleted by pushing the instrument directly out, 

 when the aqueous humor escapes, and the cornea collapses. 



The anterior waU of the crystalline coyer is then divided with 

 the kystitome (Fig. 547). The hook of which turns backwai'd, 

 and is made to tear the envelope by moving it from above down- 

 ward and from within outward. The upper lid being raised with 

 forceps, and a gentle pressure made with the finger at the lower 



