Longterm-results of pars-plana-vitrectomy in equine recurrent uveitis

Equine recurrent uveitis (ERU) is an inflammation of all parts of the uvea. The etiology and pathogenesis are not fully known. Even with optimal medical treatment the prognosis, in many cases, is not very good due to the recurring nature of the disease and the progressive destruction of the intra-ocular structures. In 1989 Werry and Gerhards introduced the surgical treatment of ERU during the inflammation free interval. in this paper, the treatment of horses with chronic recurrent uveitis by pars-plana-vitrectomy is documented. From previously operated patients, 43 eyes from 38 horses were examined in their home-stalls, with a six to sixty-Seven month interval since the operation. The examination consisted of a complete ophthalmological examination followed by measuring of the intra-ocular pressure. According to the horse-owners, 42 of the 43 eyes had no uveitic attack since the surgery. More than 70 % of the eyes retained their ability to see, with 39,5 % reporting improved vision and 32,6 % hindered vision. The most common cause for reduced vision or even blindness was a cataract in 19 eyes. The treatment through a combination of vitrectomy and phacectomy, as used in human medicine, is not yet possible in horses. A majority of the eyes (31 of 43) had a normal intra-ocular pressure. 32 of 43 pars-plana-vitrectomies had no problems whatsoever. The most frequent complication during the surgery, experienced in 4 eyes, was intra-ocular haemorrhage. Long-term complications were the development of atrophia bulbi (7 eyes), ablatio retinae (4 eyes), phthisis bulbi (2 eyes) and cataract development (19 eyes). Since chronic ocular inflammation could be the cause of these complications, it is not possible to ascribe them purely to the vitrectomy. The results of these examinations show that pars-plana-vitrectomy is a significant improvement in the treatment of equine recurrent uveitis. This treatment may improve vision and stop the progression of the uveitic destruction of the eye. In no case medical treatment should be left out of the treatment of an acute uveitic attack and also as pre-surgical measurement. it is concluded, that horses suffering from ERU should be operated on as soon as possible after the second or third attack. The suspected reason for the therapeutic effect of the pars-plana-vitrectomy is the reduction of local immunological processes through the removal of the inflammatority-changed vitreous (immunological memory of the uveitis'').