Both clinical and preclinical findings have implicated vascular endothelial growth factor (VEGF) in the pathophysiology of diabetic macular edema (DME). VEGF is both a potent enhancer of vascular permeability and a key inducer of angiogenesis. VEGF levels are elevated in the eyes of patients with DME, and in animal models of diabetes this elevation coincides with the breakdown of the blood-retinal barrier. Moreover, injection of VEGF (the VEGF165 isoform in particular) into healthy eyes of animals can induce diabetes-associated ocular pathologies.Pegaptanib, a novel RNA aptamer currently used in the treatment of agerelated macular degeneration, binds and inactivates VEGF165 and has been shown in animal models to reverse the blood-retinal barrier breakdown associated with diabetes. These findings formed the basis of a phase II trial involving 172 patients with DME, in which intravitreous pegaptanib (0.3 mg, 1 mg, 3 mg) or sham injections were administered every 6 weeks for 12 weeks, with the option of continuing for 18 more weeks or undergoing laser treatment. Compared to sham, patients receiving 0.3 mg displayed superior visual acuity (p = 0.04) as well as a reduction in retinal thickness of 68 micrometers compared to a slight increase under sham treatment (p = 0.021). These data support the use of pegaptanib in the treatment of DME.
Diabetic retinopathy (DR), a common complication of both type 1 and type 2 diabetes, is rarely expressed at a level greater than background retinopathy during childhood and adolescence. Epidemiological studies in paediatric diabetic patients together with data from the Diabetes Control and Complications Trial have demonstrated the importance of glycaemic control in delaying or preventing the development of DR; thus, the incidence of DR has declined somewhat over the past two decades. Both prepubertal and postpubertal years with diabetes contribute to the overall probability of DR development. In addition to duration of disease and degree of glycaemic control, other risk factors for DR development include elevated blood pressure, lipid profiles, serum levels of advanced glycation endproducts, evidence for early stage atherosclerosis, increased calibre of retinal blood vessels and several genetic factors, such as enzymes involved in glucose and lipid metabolism. Annual screening is recommended, with mydriatic stereoscopic fundus photography being the most sensitive detection method. Both pathophysiology and treatment in paediatric populations are essentially the same as described for adult populations, with treatment usually not required until adulthood is reached.
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