• Increase of ≥5 letters at the 5-year study visit on a LogMAR chart compared with (a) the initial baseline level and (b) the level at the 2-year study visit.
  
• Incidence of moderate or severe adverse events over the 3 years of the open-label extension
  

• Change in macular thickness by OCT
  
• Any change in visual acuity
  
• Number of laser treatments required.
  

A 25 fold increase in the risk of going blind on diagnosis of diabetes is one of the most daunting threats that patients face. People using insulin are particularly challenged because they are unable accurately to draw up their dose of drug. Most cases of vision impairment in diabetes are due to macular oedema that persists or recurs after laser treatment. There are now a number of uncontrolled, anecdotal reports that intravitreal triamcinolone (IVTA) is highly effective for the treatment of diabetic macular edema which is refractory to conventional laser treatment. We commenced the first placebo-controlled, double masked clinical trial of IVTA for refractory macular oedema in 2002. The 3 month results from this study provide the first scientific proof of principle that IVTA reduces macular thickness and improves vision. The two year results will be available in March 2005, but confidential interim analysis of efficacy data in September 2004 suggested that the beneficial effect of triamcinolone treatment persisted. Thus it appears that treatment with IVTA may be the most significant development for the prevention of blindness in people with diabetes since the introduction of laser treatment. It would also be a highly cost-effective intervention that could be administered by general ophthalmologists. The treatment cannot be recommended for routine use, however, until its long term efficacy and safety have been established. Since we already have a well studied group of patients who have received treatment for 2 years, we are in a unique position to extend the study in order to provide the long-term (5-year) safety and efficacy data that does not appear to be forthcoming from any other source. The completion of this study will have a direct and immediate effect on the risk of blindness in people with diabetes by allowing doctors to predict more accurately the long term effects of this promising new treatment.