CATARACT. OPACITY OF THE I^ENS OR ITS 

 CAPSULE. 



Definition. Forms : lenticular, capsular, cortical, nuclear, polar, black, 

 diabetic, traumatic, immature, mature, senile. Causes : impaired nutrition 

 of lens, inflammation of iris, choroid, ciliary body, retina ; recurrent oph- 

 thalmia. Proliferation of cells. Increased density, chemical changes, de- 

 generations. Sugar, sodium chloride, naphthalin. Rachitis. Senile. 

 Blood pigment. Sj'mptoms ; shrunken bulb, opalescent zone around 

 cornea, angle on upper lid, shying, extra ear activity, high stepping, better 

 sight in twilight, homatropia, examination facing the light, Purkinje's 

 images, ophthalmoscopic examination. Prognosis hopeless. Treatment : 

 phosphureted oil, massage, operation in horses, discission, under antiseptic 

 precautions, extraction under careful antisepsis, suction. 



Definition. Any pathological change in the lens or its capsule 

 diminishing its transparency. 



Varieties. The opacity may be situated either in the lens 

 (^lenticularj or in its capsule (capsular). Again, it may be in 

 the outer part (cortical) or in the central part (nuclear; of the 

 lens. If the opacity is on the capsule in front of the lens it is 

 anterior capsular ; if on the portion behind the lens it is pos- 

 terior capsular. If the opacity is caused by black iris pigment 

 adherent to the capsule it has been called black cataract. If 

 the lenticular cataract is small and round, it is polar, and it may 

 be anterior or posterior polar according as it is situated near 

 the front or back of the lens. Diabetic cataract is one associ- 

 ated with mellituria. A traumatic cataract is one resulting 

 from a wound of the lens which admits the aqueous humor and 

 causes softening, swelling and finally solution of the substance of 

 the lens. The immature or unripe cataract is one in which 

 the lens is not yet wholly involved and indurated ; the mature 

 or ripe, when such consolidation has extended throughout. 

 Senile Cataract is seen in old hor.ses, dogs, cats, birds and very 

 exceptionally in cows. This usually attacks both eyes at once. 

 A degeneration takes place in the fibres of the lens, which are 

 invaded by sclerosis beginning at the centre of the organ. 



Causes. In domestic animals cataracts are commonly the re- 

 sult of iiupairment of the nutrition of the lens in connection with 

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