BASICS
- The choroid and retina are closely related anatomically and physiologically. The choroid is the primary supply of blood to the retina. Chorioretinitis is inflammation of the choroid and retina
- Systems affected—ophthalmic
- Chorioretinitis manifests in equine eyes as “bullet-hole” retinal lesions, diffuse chorioretinal lesions, horizontal band lesions of the non-tapetal retina, and peripapillary chorioretinal lesions. Lesions near the optic disc are more likely to affect vision than peripheral retinal lesions
- Focal chorioretinopathy, or “bullet-hole” lesions, are focal or multifocal circular scars of the peripapillary and non-tapetal regions. They consist of a depigmented periphery and a hyperpigmented central area. Acute lesions, which are uncommon, appear as white or gray exudative lesions. It has been suggested that vision may be impaired if there are more than 10–20 bullet-hole lesions. However, a recent study showed that even horses with over 100 lesions per eye have not demonstrated visual impairment or changes to their retinal function, evaluated by electroretinography
- EHV-1 may be associated with “bullet-hole” lesions in horses. This type of lesion is nonprogressive, can be seen in all age groups, and is considered an incidental finding
- Diffuse chorioretinal lesions are vermiform, circular, or band-shaped lesions that are hyperreflective in the tapetal retina, and large depigmented areas in the non-tapetal retina. These lesions are uncommon. They represent prior widespread inflammatory or infarctive disease with subsequent retinal degeneration. Optic nerve atrophy may accompany these lesions, and vision is markedly reduced
- Peripapillary chorioretinitis occurs adjacent to the optic disc. Fluffy, raised exudates are found in the active stage. Vasculitis can be observed in some cases with white or pale exudates surrounding affected retinal vessels. In the chronic stage, scar tissue develops, often, but not necessarily, in a butterfly shape around the papilla. “Butterfly lesions” may be associated with ERU, especially with concurrent signs of anterior uveitis, but, unlike previously thought, they are not pathognomonic for ERU
DIAGNOSIS
TREATMENT
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FOLLOW-UP
MISCELLANEOUS