Macular edema, swelling of the center of the retina (the part of the eye responsible for our sharpest vision), is an important cause of poor vision in patients with diabetes. New forms of therapy are desirable because the current treatment including laser photocoagulation does not control all cases of diabetic macular edema (DME) and because laser therapy may destroy normal retinal tissue. Intraocular steroids in the form of intravitreal triamcinolone acetate injection (IVTA) and surgical implantation of fluocinolone acetonide (FAI) or dexamethasone drug delivery system (DDS) are promising new therapies. This systematic review included seven randomized clinical trials involving 632 eyes from five countries evaluating the effectiveness and safety of intravitreal steroids for treating DME. Two trials were at low risk of bias, one was at median risk of bias, two were at high risk of bias, and the remaining two had an unclear risk of bias. In this systematic review, the preponderance of data suggest a beneficial effect from IVTA. The average improvement in visual acuity was letters more (- LogMAR; 95% CI - to -) in the IVTA treated eyes than in those treated with other therapies at three months (based on three trials), letters more (- LogMAR; 95% CI - to -) at six months (two trials), letters more (- LogMAR; 95% CI - to -) at nine months (one trial), and letters more (- LogMAR; 95% CI - to -) at 24 months (one trial). Improved clinical outcomes were also reported in FAI and dexamethasone DDS trials. Elevation of intraocular pressure and cataract progression occur in both IVTA and implants treated eyes but appear manageable.
In most cases there is no known cause and it is not clear why it occurs. This is called idiopathic angio-oedema. Although the cause is not clear, in up to half of cases there is a link to an autoimmune disorder. These include chronic urticaria , systemic lupus erythematosus (SLE) , or an having underactive thyroid gland (thyroiditis, hypothyroidism) . In some cases there are known triggers that can cause the release of histamine, which leads to tissue swelling of angio-oedema. These include allergic reactions and non-allergic reactions to medicines .