PURPOSE: Extracellular purines play important role in ocular physiology, diabetes, vascular remodelling and adaptation to inflammation. This study was aimed to evaluate intravitreal purine levels in patients with diabetic retinopathy (DR) and other non-vascular vitreoretinal eye diseases. METHODS: Vitreous samples were collected at the start of the three-port pars plana vitrectomy. Study group comprised 55 eyes operated due to sight-threatening forms of DR, including eyes of 24 patients with proliferative DR. Of the 143 non-diabetic controls, 112 had rhegmatogenous retinal detachment and 31 macular hole or pucker. Intravitreal purine concentrations were determined using a combination of bioluminescent [adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP)] and fluorometric [adenosine 5'-monophosphate (AMP), adenosine, inosine] enzyme-coupled sensing assays. RESULTS: Compared with non-diabetic controls, DR eyes contained significantly higher (p < 0.01) concentrations of ATP (4.2 +/- 0.6 versus 34.5 +/- 13.7 nm; mean +/- SEM), ADP (19.5 +/- 2.7 versus 43.7 +/- 14.5 nm) and AMP (1290 +/- 115 versus 1876 +/- 190 nm). Intravitreal adenosine and inosine levels varied within submicromolar to low micromolar range, and their concentrations did not differ between the groups studied. CONCLUSIONS: High concentrations of intravitreal nucleotides ATP, ADP and AMP may be related to the pathogenesis of sight-threatening forms of DR.