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Show 4.3 01" IKE EXTRACTION 01" Till} CATARAC'L a- 1." -,---.-v ~-- . . t, .. =:, .‘ ,vvv,‘r ~ _. 4:» :z-ra ".- .m _.7 ly forward, we must insinuate one of the blades of the fine scissors under the flap of the cornea, and enlarge the incision. 10. I shall suppose that the section of the cornea has been duly made, and the cataract does not immediately follow. Some oculists have recommended that we introduce a curette into the pupil, and enlarge it. This is an ignorant w ay of dilating the pupil. We ought simply to shut the eyelids, and cover the eye with the hand, so as to relieve the excite. ment of the eye, and by excluding the light the pupil will be dilated, and ten to one but the cataract will be seen coming from under the eyelids, on lifting up the flap of the cornea.- If the cataract be still retained, then it is not the contraction of the pupil which prevents its discharge, but a particular strength in the capsule. And now the gold needle, or some such instrument, must be passed under the flap of the cornea, and into the pupil, to break or puncture the capsule, when the cataract will be discharged. 11. The Baron \Venzel and other oculists who have gained dexterity by practice, without ascertaining the principle, have asserted that " The incision of the cornea is not the most difficult part of the operation, and that it afterwards requires much dexterity as well as judgment successfully to extract the cataract." All that I know of the structure of the eye, and what I have seen of these operations, and the diliiculties I have myself experienced, contradict this opinion. The successful incision of the cornea is the operation, and all the untoward circumstances that may trouble the operator, have their source in the imperfection of the section of the cornea, or from some previous disease of the eye, as for example, the thickening of the membranes, or the adhesion of the capsule of the lens to the iris, Sec. .s'nj- u'i‘gvgug'.' f.~'.\.<. .4 rd". . .. A. As soon as the knife has cut itself out, the upper eyelid should be allowed to fall ; for the uniform support of the eyelid prevents the cataract from being thrown out too quickly, or the vitreous humour from following it, if it should escape before the eyelid can be closed. If upon raising the eyelid fhc [ens docs not make its appearance, the capsule is to be on THE EXTRACTION or THE CATARACT. punctured, and the eyelids again closed to allow the pupil to dilate. If it does not now come forward, the small probe is to be introduced under the flap of the cornea, to examine if the incision be large enough; for, from the thickness of the cornea and the oblique direction of the knife, the incision of the cornea may seem to be of sufficient length on the surface of the cornea, when the knife has not penetrated to the inner surface nearly to the same extent: if the incision should prove too small, it must be a little enlarged with the scissors, as I have said. If the cataract does not now come out spontaneously when the incision is evidently sufficient, and when the capsule is punctured, we are forced to press the eyeball. , 12. We ought not to press the eyeball if it can be avoided; for there being a difficulty in forcing the cataract through the pupil, when that difficulty is overcome the vitreous humour is apt to follow the cataract; and often it will happen, that the Vitreous humour will escape without the lens being discharged. By this pressure the lens is not carried through the pupil, but only the edge of it is pro- truded, and the vitreous humour escapes under it, while the firmer cataract is retainedit. 13. When the iris is cut by the edge of the knife, no pressure must be made on the eyeball, or the Vitreous humour will escape while the cataract is retained. When the pupil is of its natural form, and the iris entire, the cataract presents behind the pupil, and no part of the vitreous hu4* Thus we find the Baron dc VVenzel describing a thing which should never be seen-" The cataract did not give way to the gentle pressure that is usually found sufficient to dislodge it. Its upper edge repeatedly advanced into the pupil, and sometimes almost came through Lt," 8:0. Every time the crystalline advanced, a small bladder was per- ceived on its posterior and inferior edge, strongly adherent to it, and formed by the hyaloid membrane, &c. To press the eyeball in such a state of the lens, and the bladder which is here described, is out of all rule. The bladder is simply the vitreous humour pushing forth under the lens or cataract, which has turned its edge forward instead n',‘ being carried bodily through the pupil. VOL. II'. '7 49 H |