Retinal photocoagulation does not influence intraocular levels of IGF-I, IGF-II and IGF-BP3 in proliferative diabetic retinopathy - Evidence for combined treatment of PDR with somatostatin analogues and retinal photocoagulation?

Retinal photocoagulation reduces the incidence of severe visual loss in pro liferative diabetic retinopathy (PDR). Reduced levels of VEGF/VPF might res ult in an improved function of the blood-retina barrier and cause a decreas e of blood derived intraocular growth factors such as IGF-I. This study inv estigates whether retinal photocoagulation is able to normalize the concent rations of IGF-I, IGF-II and IGF-BP3 in the vitreous humor of patients unde rgoing vitrectomy. Levels of IGFs and the permeability marker, albumin, wer e measured in serum and vitreous of 52 patients. Three groups were compared : controls without proliferating eye disease (n = 19) and patients with PDR with (PDR+; n = 25) and without (PDR-; n = 8) previous retinal photocoagul ation. IGF-l, IGF-II, IGF-BP3 and albumin were determined by immunological methods and were confirmed to be increased in patients with PDR compared to controls. Retinal photocoagulation influenced neither the intraocular conc entration of the permeability marker albumin (PDR+: 253.2 +/- 46 mg/dl; PDR -: 256.4 +/- 66.5 mg/dl) nor the levels of IGFs (PDR+: IGF-I: 1.2 +/- 0.1 n g/ml; p = 0.38; IGF-II: 34.8 +/- 2.2 ng/ml; p = 0.1; IGF-BP3: 75.7 +/- 9.7 ng/ml; p = 0.27; PDR-: IGF-I: 1.1 +/- 0.2 ng/ml; IGF-II: 29.3 +/- 5.2 ng/ml ; IGF-BP3: 61.5 +/- 18.3 ng/ml). Systemic levels of albumin and IGFs were n ot changed significantly by retinal photocoagulation. These results demonst rate that previous retinal photocoagulation in patients undergoing vitrecto my does not functionally reestablish the blood-retina barrier despite decre ases in VEGF/VPF. The lack of influence on intraocular concentrations of th e serum-derived growth factors, IGF-I, IGF-II and IGF-BP3, might in part ex plain the failure of previous photocoagulation in the investigated patients . These results suggest that a combined treatment with retinal photocoagula tion and growth hormone-lowering drugs, such as somatostatin analogues, cou ld be a useful treatment, which may prevent further loss of visual acuity i n patients with PDR.