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Discussion on Pupil doesn't dilate
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New Member: savvyjes
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Posted on Saturday, Jan 26, 2008 - 5:48 pm:
I have a 3 year old TB filly whose left eye doesn't dilate. In fact you can barely see the pupil at all, it's all brown, with just a tiny dark line where the pupil is. There is no redness, swelling, tearing, cloudiness or any other normal signs of eye problems. The eye is set a little more into her head than her normal right eye, and sometimes in the right light it appears to be just slightly cast over. She is very flighty, especially about things behind her, but is very calm in comfortable places, such as her stall. Walking from shadowy places to bright ones is very difficult for her also. I have read the description of night blindness and glaucoma, and she doesn't have those kind of symptoms. Are there any other possibilities?
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Moderator: DrO
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Posted on Sunday, Jan 27, 2008 - 10:15 am:
Hello jesse, This is most often caused by fibrous scars that have formed across the iris or even possibly between the iris and surrounding structures, ie synechia. As these fibrous attachments contract they close the pupil. This effectively limits the vision to the degree that the pupil is closed. The important question in such cases is, "why have the scars formed". Often this complication will accompany other eye diseases that do result in true retinal blindness. The fact the eye appears smaller is not a good sign that there is not greater damage than the small pupil alone. To resolve these issues will require an examination by an ophthalmologist and may require advanced diagnostic techniques but if the rest of the eye is OK there may be treatments available to open the iris. DrO
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