Retinal detachment secondary to vitreoretinopathy in two closely related warmblood horses

BACKGROUND: To describe the clinical, diagnostic imaging, and histopathological findings of two visually impaired closely related horses and to identify a possible cause. CASE DESCRIPTION: Two warmblood horses, with a common dam and sire, were presented to the ophthalmology department of Liège for investigation of impaired vision. Information collected included physical and ophthalmic examination findings, results of ocular ultrasound, electroretinogram, magnetic resonance imaging (MRI), and histopathology. Ophthalmic examination, ocular ultrasound and MRI revealed a complete retinal detachment (RD) in the left eye and vitreous synaeresis in both eyes of both horses. Electroretinograms showed a normal response in both right eyes but a total loss of the retinal response in their left eyes. Histopathologic examination revealed multifocal retinal dysplasia in both left eyes. CONCLUSION: In these two horses, RD has likely been caused by the congenital posterior segment abnormalities of the vitreous and the retina. A vitreoretinopathy is highly suspected and is possibly hereditary in these closely related siblings.