A large-scale study analysing data from diabetic patients has demonstrated that diabetic retinopathy (DR) progression and diabetic macular oedema (DMO) development increase with higher DR severity and there appears to be distinct clinical subtypes.
Dr Geeta Lalwani, from Rocky Mountain Retina Associates in the US, presented the study at the 2020 virtual meeting of the American Academy of Ophthalmology. “Among these patients who progressed with diabetic retinopathy, we found them to have distinct clinical subtypes – they either developed DMO or proliferative DR (PDR). However, very few developed both,” she said. “In other words, even patients who had severe non-proliferative diabetic retinopathy (NPDR) at baseline within five years still seemed to develop either DMO or PDR, and typically not both. We would have expected that more severe patients would have gotten more severe in every way, but that wasn't true.”
In seeking to explain these differing diabetic responses, Dr Lalwani pointed out the high concordance in twin studies in the severity of diabetic retinopathy from one twin to the other twin. There are certain genes that seem to be implicated in developing either PDR or DMO. Some of the systemic factors that the study focused on seem to have had no effect on the development of DMO versus PDR, she explained.
The study included approximately 42,000 eyes, with the 22,000 patients being predominantly male (83%) and having type-2 diabetes (94%). Nearly 50% of the population was Caucasian. Native Americans comprised 41% of the group. The data under review included seven-field colour fundus images collected between 1999 and 2016 in the Inoveon database of patients with diabetes. Eligible patients had at least two gradable images in either eye from two different time points. The severity of DR was graded using the Early Treatment Diabetic Retinopathy Study (ETDRS). DR Severity Scale (DRSS) and presence of CSME were assessed by professional graders at a centralised reading centre.
“Our finding of different clinical subtypes among eyes with DR suggests that PDR and DME may represent two distinct disease processes potentially driven by distinct genetic factors,” said Dr Lalwani. “Several potential genes have been associated with DR pathogenesis, including those associated with angiogenesis and inflammatory pathways, and these appear to result in different phenotypes. More research is needed on the clinical and genetic factors responsible for these distinct risks of DMO versus PDR development in patients with type-2 diabetes.”
