Sir,

Approval of ranibizumab for diabetic macular oedema (DMO) has resulted in a growing number of patients with diabetic retinopathy (DR) attending so-called ‘macular clinics’ for regular follow-up and intravitreal treatment. These one-stop clinics were originally established to cater for patients with neovascular age-related macular degeneration.

Case report

We present the case of a 48-year-old type 1 diabetic who was referred to our macular treatment centre in early 2012 for diffuse DMO that had not responded to macular laser. Over a 12-month period, he received multiple bilateral injections of ranibizumab. His DMO settled completely in both eyes and his vision improved to 6/9 bilaterally. In mid-2013, it was decided that further intravitreal treatment was no longer necessary given that both maculae were dry. Follow-up was arranged but at a longer interval of 4 months. When seen in late 2013, bilateral florid neovascularisation with high-risk characteristics was evident. Urgent bilateral, complete panretinal photocoagulation (PRP) was undertaken.

Comment

Ischaemia of the peripheral retina has long been hypothesised to have a role in the development of DMO.1 In DR, ischaemia leads to the release of vascular endothelial growth factor (VEGF) that causes breakdown of the blood–retina barrier.2 This, in turn, leads to increased vessel permeability that may be the cause of DMO.3 We believe that our patient probably developed bilateral macular oedema on account of co-existing peripheral ischaemia, which was clinically evident as severe non-proliferative disease. This diagnosis had already been made at the time of referral for intravitreal treatment. Early PRP, administered during or before intravitreal anti-VEGF treatment, could have prevented the development of sight-threatening high-risk proliferative disease.

We also believe that there may be many more patients like ours within fast-track macular pathways across the country who are at risk of suddenly developing proliferative disease upon cessation of intravitreal anti-VEGF therapy. Patients with DMO who are PRP-naive and undergoing intravitreal treatment within such pathways (macular clinics) should have close monitoring with an examination of the peripheral retina at every visit.