46 patients with the association of acute anterior uveitis and the presence of HLA B27 antigen were studied. Ankylosing spondylitis was found in 19 patients (41.3%). Ophthalmoscopy showed a diffuse vitreous haze in 63%, a macular disease in 21.7%, a papillitis in 17.4%. We performed pars plana vitrectomy on 8 patients (10 eyes) with severe posterior uveitis and/or cystoid macular edema. The postoperative follow-up period averaged 14 months with visual acuity improvement in 5 eyes. The surgical indications are described.