SURGERY. 211 



lens or its capsule by which vision is obstructed either totally or partially. 

 When the lens alone is aflecteJ, the cataract is lenticular- ; when the cap- 

 sule alone, capsular ; and capsulo-leuticular when both are concerned. 



In operating for cataract, the lower eyelid is to be drawn downwards and 

 outwards by the index and middle finger of the left hand of the operator, 

 while an assistant supports the chin with his left hand and holds back tho 

 upper eyelid with his right. 



All the different operations for cataract have as their object the displace- 

 ment of the lens and capsule. This is effected either by removal through 

 the cornea or sclerotic, by pushing to one side, or by cutting into pieces so 

 as to cause the absorption of the fragments. 



a. Extraction. This operation involves three stages : 1, the opening of 

 the e3^eball by means of semilunar incisions in the cornea ; 2, the opening 

 of the capsule ; and 3, the removal of the lens through the pupil. The inci- 

 sion is made with the cornea knife, the form of which varies greatly (^;^. 

 140, ßg. 59, Beer's knife; ßg. 57, Bell's knife; ßg. 58, Sharp's knife). 

 The right eye must be operated with the left hand, the left with the right 

 {pi. 139, ßg. 10, operator with Beer's knife ; ßg. 11, do. with the double 

 knife of Jäger). Jäger's knife is asserted to have the advantage of causing 

 a wound which heals sooner, and without as much probability of the pro- 

 trusion of the iris and vitreous humor. A modification of Jiiger's knife 

 {pi. 140, ßg. 61) has been proposed by Ott. After the incision has been 

 made through a little more than one half of the circumference of the cornea 

 almost close to the sclerotic, the upper eyelid is to be dropped for a few 

 seconds, and then carefully raised for the introduction of the instrument 

 intended to open the capsule. This is best effected by the lancet-shaped 

 cataract needle. Instruments called cystitomes {fig. 60, La Faye's as 

 improved by Richter) have been recommended by some, but they are liable 

 to serious objections. Three or four vertical and several transverse 

 scratches of the capsule are now made with the cataract needle. The lens 

 will then usually come out of the capsule, but may require the assistance 

 of a gentle pressure. Various attempts have been made to extract the 

 capsule with the lens, and for this purpose different forceps have been 

 invented, such as Beer's forceps, {ßg. 44), Graefe's do. {ßg. 45), Maunoir's 

 do. {ßg. 46). The experiment of making the entrance through the scle- 

 rotic has been attended with considerable difiicullies and dangers, so that 

 the present method is most generally employed, excepting where the next 

 mentioned is preferred. 



b. Keratomjxis consists in the introduction of a needle through the cornea 

 for the purpose of breaking up the cataract, separating it from its connex- 

 ion-;, in order that it may be dissolved and absorbed ; or else to depress it 

 and thus force it out of the axis of vision. The latter operation is more 

 correctly termed couching. 



Both curved and straight needles may be used in these operations ; the 

 former, however, are preferred. The operator pierces the lower part of the 

 cornea, far enough from its border to clear the pupillary margin of the iris 

 {pim.fg.ll). 



917 



