Clinical Equine Ophthalmology Practice Test

Chorioretinitis causes inflammatory damage to the choroid and retina, leading to scarring and loss of pigment. In horses, this most often shows up as pale, depigmented areas in the non-tapetal retina around the optic disc. The tapetum lucidem is a separate layer, and chorioretinal inflammation typically does not present as hyperpigmentation of the tapetum. Thickening of the sclera or vascular shunting are not characteristic fundoscopic signs of chorioretinitis. So the depigmentation in the non-tapetal retina around the disc is the classic, most consistent change you’d expect.