Special indications for vitrectomy in horses

Abstract

In Germany, the surgical removal of as much vitreous as possible (vitrectomy) is a common treatment of equine recurrent uveitis (ERU). Intraocular leptospiral infection has been found to be the reason for an immune-mediated reaction which finally causes the typical signs of ERU. Inflammatory clumps, inflammatory mediators and leptospires are removed from the vitreous body in order to eliminate further attacks. Recurrent uveitis is still the major indication for performing vitrectomy in the horse. Generally, an optimal outcome should be the restoration of a normal vision in horses with mild intraocular changes. Due to a large caseload in our clinic, we can report about the application of vitrectomy in severely affected eyes as well. In 16 out of 21 surgically treated hypotensive globes, we were able to preserve the eye and to avoid further shrinkage (70.2%). In contrast, the number of grave complications (septic endophthalmitis, panuveitis) resulting in final enucleation related to the total number of surgeries (499) is below 2%. We performed vitrectomy in two horses with glaucoma as well. Glaucoma is usually a sequela or a complication of uveitis. In both cases the surgical approach resulted in decreasing the previously high intraocular pressure (from 56 to 29 mm Hg and from 74 to 34 mm Hg, respectively). The long lasting corneal opacities almost cleared up and the final outcome is still good even after several years. Although most of the affected eyes remain blind after surgery, the opportunity to make the globe painless for the horse should be kept clearly in mind. Another indication for using vitrectomy are vitreal "floaters", if horses find them distracting and frightening. Particularly sport horses can spook suddenly, refuse to complete performance tasks and generally act distracted. Before surgery it is necessary to rule out all other possible reasons for the behavioural problem. The development of these opacities seems not to be related to equine recurrent uveitis, because no laboratory evidence of leptospirosis and no inflammatory signs of the inner ocular structures could be seen yet.