269 



INTERNAL OPHTHALMIA — IRITIS— CHOROIDITIS — RETINITIS. 



Althoiigli inflammations of the iris, choroid, and retina, the inner, 

 vascular, and nervous coats of the eye, occur to a certain extent inde- 

 l^endently of each otlier, yet one usually supervenes upon the oilier, 

 and as the symptoms are thus made to coincide it will be best for our 

 present purposes to treat the three as one disease. 



The causes of internal ophthalmia are largely those of the external 

 form only, acting- Avith greater intensity or on a more susceptible eye. 

 Severe blows, bruises, punctures, etc., of the eye, the penetration of 

 foreign bodies into the eye (thorns, splinters of iron, etc.), sudden 

 transition from a dark stall to bright sunshine, to the glare of snow or 

 water, constant glare from a sunny window, abuse of the overdraw 

 check-rein, vivid lightning flashes, draughts of cold, damp air; above 

 all, when the animal is persi^iring, exposure in cold rain and snow- 

 storms, swimming cold rivers, also certain general diseases like rheu- 

 matism, arthritis, influenza, and disorders of the digestive organs, may 

 become complicated by this affection. From the close relation between 

 the brain and eye — alike in the blood vessels and nerves — disorders of 

 the first lead to affections of the second, and the same remark applies 

 to the persistent irritation to which the jaws are subjected in the course 

 of dentition. So potent is the last agency that we dread a recurrence 

 of ojDhthalmia so long as dentition is incomplete, and hope for immu- 

 nity if the animal completes its dentition without any permanent 

 structural change in the eye. 



The sympioms will vary according to the cause. If the attack is due 

 to direct physical injury the inflammation of the eyelids and suijerfi- 

 cial structures may be quite as marked as that of the interior of the 

 eye. If, on the other hand, from general causes, or as a complica- 

 tion of some distant disease, the affection may be largely confined to 

 the deeper structures, and the swelling, redness, and tenderness of the 

 superficial structures will be less marked. When the external coats 

 thus comparatively escape the extreme anterior edge of the white or 

 sclerotic coat where it overlaps the border of the transparent cornea is 

 in a measure free from congestion, and, in the absence of the obscuring 

 dark jjigment, forms a Avhitish ring around the cornea. This is j^artly 

 due to the fact that a series of arteries (ciliary) passing to the inflamed 

 iris j)enetrate the sclerotic coat a short distance behind its anterior 

 border, and there is therefore a marked difference in color between 

 the general sclerotic occupied between these congested vessels and 

 the anterior rim from which they are absent. Unfortunately the pig- 

 ment is often so abundant in the anterior part of the sclerotic as to 

 hide this symptom. In internal ophthalmia the opacity of the cornea 

 may be confined to a zone around the outer margin of the cornea, and 

 even this may be a bluish haze rather than a deep fleecy white. In 

 consequence it becomes possible to see the interior of the chamber 



