Regarding: Diabetic macular ischaemia is associated with narrower retinal arterioles in patients with type 2 diabetes

Abstract

I read with great interest the article ‘Diabetic macular ischaemia is associated with narrower retinal arterioles in patients with type 2 diabetes’ by Liew et al. (2015). The authors should be congratulated on this important article regarding diabetic macular ischaemia (DMI) which is a severe vision-threatening condition, even in the anti-VEGF era. The main finding of the article was an independent association between central retinal arteriolar narrowing and DMI. Retinal vascular calibres are important non-invasive biomarkers which are predictive of early-stage (Cheung et al. 2008) as well as end-stage diabetic retinopathy (Broe et al. 2014). However, observations regarding retinal vascular calibres and diabetic macular oedema (DMO) or DMI are still limited. In a retrospective study of 69 eyes from patients with DMO, we found a decrement in macular retinal arteriolar and venular calibres 6 months after focal/grid laser treatment (Lundberg et al. 2013). On the other hand, we did not find a statistically significant change in central retinal arteriolar or venular diameter. Liew et al. (2015) elegantly demonstrated an inverse association between DMI severity and central retinal arteriolar diameter, but this was no longer statistically significant when patients who had panretinal photocoagulation (PRP) were excluded. Panretinal photocoagulation is considered an important confounder because it has been demonstrated that patients who had PRP were more likely to have central retinal arteriolar narrowing (Grauslund et al. 2009). Given that central retinal arteriolar vessel calibres are measured around the optic disc, these might be considered a more ‘global’ measurement of retinal function. Did the authors consider expanding the observations to macular calibre measurements given that this could be a more sensitive marker of macular perfusion?