Internal Ophthalmia. 393 



Causes. Many of the causes of conjunctivitis, when acting 

 with special intensity, or for too long a time, may cause internal 

 ophthalmia. Severe blows, bruises, punctures, lacerations, sand, 

 cinders, dust, lime, foreign bodies inducing traumas, sudden 

 transitions from darkness to bright sunshine, habitual exposure 

 to sunshine or to the reflection from snow, ice or water, through 

 a window in front of the stall, the abuse of the overdraw check 

 rein, the glare of electric light or of lightning flashes, draughts 

 of cold damp air between windows or doors, the beating of cold 

 storms on the eyes and skin, a sudden chill from plunging in 

 water or standing in a cold draught when perspiring, blows with 

 branches, pine cones or needles in the eye, the constant irritation 

 from entropion, trichiasis, burdocks or thistles in the forelock, 

 irritant gases, etc., are among the factors which cooperate in 

 setting up the disease. Again diseases of the digestive organs, 

 rheumatism, influenza, canine distemper, brustseuche, petechial 

 fever, variola, eczema, and aphthous fever may be direct causes. 

 Conjunctivitis and ksratitis are liable to merge into irido-choroidi- 

 tis by extension, and above all when owing to perforation 

 of the cornea a direct channel is opened for the easy entrance of 

 infective, pathogenic microbes. A lymphatic constitution, con- 

 nected with low breeding, or living in a low, damp, cloudy region, 

 or in dark, damp, impure stables, has a strongly predisposing in- 

 fluence. The period of dentition, connected as it usually is with 

 domestication, stabling, grain feeding', and training is often a 

 potent accessory cause. 



Symptoms. With the general phenomena of superficial or ex- 

 ternal ophthalmia there are some indications which may be called 

 pathognomonic. These may be summarized as follows : in eyes 

 devoid of pigment the enlarged ciliary vessels run deeply and are 

 not tortuous, nor mobile when rubbed ; the scleral redness increases 

 toward the margin of the cornea, but leaves a white zone in front 

 of the penetration of the ciliary vessels ; the iris has lost its clear re- 

 flection, appearing dull or brownish ; the pupil is contracted and 

 sluggish in response to light and darkness, it may be fixed or may 

 ■show marked unevenness in its margin : the tension of the eye ball 

 is often increased, flocculi of lymph may be seen in the aqueous humor 

 settling into the lower part of the anterior chamber. This deposit 

 may be white or yellowish or it niay.even be reddened by ex- 



