The equine fundus. III: Pathological variants.

A wide range of ophthalmoscopic variants are encountered during routine examination of the horse. Some result from minor anatomical anomalies, cause no significant effect on vision and may be considered to lie within the limits of 'biological normality'. Others are a consequence of pathological disruption of the anatomical integrity of the fundus, and may directly or indirectly affect the neurosensory retina and produce some degree of visual deficit. This paper illustrates the ophthalmoscopic appearance of a number of pathological variants of the anatomic fundus, and discusses their possible effect upon vision. Among the abnormalities discussed is peripapillary chorioretinitis, which commonly presents as the so-called peripapillary 'butterfly lesion'. It is concluded that, although this lesion may occur in conjunction with signs of more generalised posterior segment disease, eg posterior capsular cataract, in the absence of concurrent signs of anterior uveitis there is no reason to associate the lesion with equine recurrent uveitis (periodic ophthalmia).