The authors quite rightly point out that quantification of retinal ischaemia has the potential to serve as a biomarker for diabetic retinopathy disease progression. They set out to investigate the relationship between area of ischaemia on a swept source OCTA and severity of diabetic retinopathy. A combination of a manual and automated method of non-perfusion area calculation was used when analysing the OCTA images. Seventy-three eyes were included for analysis. Of the 73 eyes, 28 eyes had no clinical evidence of retinopathy, nine eyes were graded as mild non-proliferative diabetic retinopathy (NPDR), 10 eyes as moderate NPDR, five eyes as severe NPDR, and 21 eyes as proliferative diabetic retinopathy (PDR). Diabetic macular oedema was present in one of the 10 eyes with moderate NPDR, two of the five eyes with severe NPDR, and eight of the 21 eyes with PDR. In eyes without DR, the mean percentage area of non-perfusion was 0.1%, in the NPDR eyes (mild, moderate, and severe), the mean percentage area was 2.1% in the PDR eyes, and the mean percentage area was 8.5%. The percentage of area of ischaemia increased in a statistically significant manner from eyes without DR, to eyes with NPDR, to eyes with PDR. Within the PDR group, the mean percentage area of non-perfusion was 12.5% when macular oedema (ME) was present, compared with 7.5% when ME was absent. This difference was not found to be statistically significant. In keeping with results from previous OCTA and FFA studies, this paper showed that there is a statistically significant increase in the percentage of non-perfusion area as DR severity increases.