Background: Diabetic retinopathy (DR) is characterized by blood-retina barrier breakdown induced by local changes in the retina and systemic factors. We investigated vitreous and serum levels of glucose and uric acid (UA) in patients with DR and aimed to describe their correlation with the grade of DR. Methods: Prospective study of 81 patients with DR and 48 non-diabetic controls. Biochemical analysis of vitreous and serum samples was performed. Results: UA and glucose concentrations in vitreous and serum were significantly higher in diabetic patients than in controls. Absolute ratios (vitreous level/serum level) of UA and glucose were higher in proliferative compared with non-proliferative DR. Conclusions: The results suggest that, apart from glucose, increased levels of UA in diabetic patients may also be involved in the pathogenesis and progression of DR.

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Pars plana vitrectomy (PPV) with silicone oil implantation (SOI) was performed for advanced proliferative diabetic retinopathy (PDR) in 110 eyes of 98 diabetic patients. In 77 eyes (70%) it was a primary SOI as part of the initial operation; in 33 eyes (30%) it was a secondary SOI in reoperations. Indications for SOI were traction retinal detachment of the posterior pole, combined traction and rhegmatogenous detachment, vitreous haemorrhage with florid vascularised fibrous proliferations, and recurrent vitreous haemorrhage after PPV. The patients were followed up for 24 to 72 months, with a mean of 53 months. At the end of follow-up, anatomical success was achieved in 63 eyes (57%), and functional success with visual acuity 0.01 and better in 35 eyes (32%). Functional failures were caused by retinal redetachment in 47 eyes (43%), by secondary glaucoma in 10 eyes (9%), retinal ischemia in 15 eyes (13%) and keratopathy in three eyes (3%). The functional success rate decreased with follow-up from 67% after six months to 50% by 60 months after SOI. Silicone oil bubble in the anterior chamber, rubeosis iridis, cataract, and glaucoma were the most frequent postoperative complications. PPV with SOI was highly effective in many serious complications of advanced PDR. Functional success was mostly lasting and markedly improved the quality of life of these patients.

Pars plana vitrectomy with carefully selected testing is a valuable tool for assessment of diagnosis in a large proportion of patients with uveitis. Moreover, the therapeutic effect of vitrectomy can improve the visual outcomes in these patients.