SURGERY. 211 
lens or its capsule by which vision is obstructed either totally or partially. 
When the lens alone is affected, the cataract is lenticular ; when the cap- 
sule alone, capsular ; and capsulo-lenticular 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 the 
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 eyeball by means of semilunar incisions in the cornea; 2, the opening 
of the capsule; and 8, the removal of the lens through the pupil. The inci- 
sion is made with the cornea knife, the form of which varies greatly (pi. 
140, jig. 59, Beer’s knife; jig. 57, Bell’s knife; jfig. 58, Sharp’s knife). 
The right eye must be operated with the left hand, the left with the right 
(pl. 189, fig. 10, operator with Beer's knife; fig. 11, do. with the double 
knife of Jiiger). Jiiger’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 Jiger’s knife 
(pl. 140, jig. 61) has been proposed by Ott. After the incision has been 
made through a litle 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 lable 
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, (fig. 44), Graefe’s do. (fig. 45), Maunoir’s 
do. (fig. 46). The experiment of making the entrance through the scle- 
rotic has been attended with considerable difficulties and dangers, so that 
the present method is most generally employed, excepting where the next 
mentioned is preferred. 
b, Keratonyxts consists in the introduction of a needle through the cornea 
for the purpose of breaking up the cataract, separating it from its connex- 
ions, 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 
(pl. 139, fig. 12). 
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