A Multicentre Randomised Clinical Trial of Laser Treatment Plus Intravitreal Triamcinolone for Diabetic Macular Oedema

A 25 fold increase in the risk of going blind on diagnosis of diabetes is one of the most daunting threats that people with diabetes face. Stimulated by several uncontrolled, anecdotal reports, we are already conducting a randomized clinical trial of intravitreal triamcinolone for the treatment of diabetic macular edema which is refractory to conventional laser treatment. The analysis of the 3 month data from this study has already unequivocally demonstrated that the treatment very significantly reduces or eliminates macular oedema in the short term and results in improved visual acuity. Thus intravitreal triamcinolone may represent the most significant development in the prevention of blindness in people with diabetes since the introduction of laser treatment. It is also a highly cost-effective intervention that can be administered by general ophthalmologists. The next question to be answered, which will be addressed directly by the present study, is whether there is a significant, synergistic beneficial effect when intravitreal steroids are combined with current therapy (laser).

This study represents the second major project to be undertaken by the Australian Retinal Collaboration (ARC). The ARC aims to set the highest attainable standards for investigator-initiated clinical research in retinal diseases in Australia. Having enrolled and treated more than the target of 120 patients, we are currently completing an RCT of laser induced chorioretinal anastomosis for central retinal vein occlusion, an innovative Australian concept for a severe and otherwise untreatable disease. The proposed study is likely to identify an improved and economical treatment for one of the commonest causes of blindness both in Australia and the rest of the world. Intravitreal triamcinolone is also an intervention which has generated intense interest internationally, and one for which members of the ARC are acknowledged pioneers.

Successful implementation of the study proposed, which is feasible, is highly likely to have an immediate and direct effect on the prevention of vision impairment and blindness in people with diabetes

Inclusion criteria

• Age >= 18 years
• Diagnosis of diabetes mellitus types 1 or 2
• Diabetic macular oedema affecting the fovea in one or both eyes (phakic or pseudophakic) for which laser treatment is indicated in the opinion of the investigator
• Best corrected visual acuity of 19-68 letters (6/12 -6/120)
• Definite macular oedema on clinical examination involving the centre of the macula
• Retinal thickness > 250 micron in central 1mm subfield on OCT
• Investigator is comfortable deferring macular laser treatment for 6 weeks

Exclusion criteria

• Glaucoma which is uncontrolled or is controlled but with glaucomatous field defects
• Loss of vision due to other causes (e.g. age related macular degeneration, myopic macular degeneration, retinal vein occlusion)
• Macular oedema due to other causes including vitreous traction
• An ocular condition that would prevent visual acuity improvement despite resolution of oedema (such as foveal atrophy)
• Previous treatment IVTA within 6 months or with peribulbar TA within 3 months
• Cataract surgery within the last 6 months
• Retinal laser treatment within the last 4 months
• High risk PDR at baseline or laser therapy cannot be delayed for 6 weeks on retina
• History of herpes viral disease in study eye
• Media opacity including cataract that already precludes adequate macular photography and laser treatment, or cataract that is likely to preclude an adequate view within 2 years
• Known allergies to triamcinolone acetate
• Patient is already receiving systemic steroid treatment
• Intercurrent severe disease such as septicemia, any condition which would affect follow-up or photographic documentation (e.g. geographical, psycho-social)
• History of chronic renal failure requiring dialysis or renal transplant
• Blood pressure >180/110 mmHg