Diffuse retinal thickness and epiretinal membrane important imaging biomarker for DR

DR naturally progresses from non-proliferative abnormalities to proliferative diabetic retinopathy (PDR), characterized by neovascularization involving disc (NVD) or neovascularization elsewhere (NVE). The leading cause of vision loss in DR patients is Diabetic Macular Edema (DME). DME is characterized by retinal thickening and edema, which can develop in all stages of retinopathy. Many studies and clinical trials have confirmed significant risk factors for DME, such as hyperglycemia, dyslipidemia, hypertension, smoking, and nephropathy. There are many biomarkers to assess these risk factors for DR and DME. It can be clinical (general and ocular), imaging, biochemical, and molecular

One of the imaging modalities used to assess DR and DME is OCT. It is a non-invasive, non-contact method for assessment of macular edema and each feature observed in OCT acts as an imaging biomarker. The biochemical biomarkers considered are glycosylated hemoglobin (HbA1c), total cholesterol, serum low-density lipoprotein (LDL), serum high-density lipoprotein (HDL), total triglycerides, serum creatinine, serum urea and microalbuminuria.

The relationship between different biomarkers and stages of DR and DME will be necessary for optimal clinical management and new clinical strategies to prevent vision loss. However, no studies have established a strong association between these biomarkers in different stages of DR. In this study, Naveen et al compared these biomarkers for DME in various stages of DR and their association with each stage of DR.

It was a cross-sectional, observational study that included 100 patients of DME with different stages of DR. Patients were divided into two groups: Group A – DME with non-proliferative diabetic retinopathy (NPDR) and Group B - DME with proliferative diabetic retinopathy (PDR). Group A was further subdivided into three subgroups: A (1) – DME with mild NPDR, A (2) – DME with moderate NPDR, and A (3) – DME with severe NPDR. The primary outcome measure was the association of imaging and biochemical biomarkers with different stages of DR in patients with DME.

Out of 100 patients, Group A (1) had 1, Group A (2) 44, Group A (3) 29, and group: B had 29 patients. The HbA1c levels, serum triglyceride level, serum cholesterol level, and microalbuminuria level showed no significant association with different stages of DR (P>0.05).

Still, authors found high serum urea levels (p=0.027) in Group B patients. The optical coherence tomography (OCT)-based imaging biomarkers – central subfield thickness (CST), cystoid macular edema (CME), subretinal fluid (SRF), and hyperreflective foci (HRF) – showed no significant association with various stages of DR. The presence of diffuse retinal thickness (DRT) (p=0.04) and the epiretinal membrane (ERM) (p=0.04) showed significant association with Group B patients.

DR can be defined as prolonged hyperglycemia leading to retinal microvascular damage. This internally leads to DME, a common cause of vision loss and visual disability worldwide. DME is a preventable cause of vision loss; elucidating and preventing the risk factors of DME can go a long way in reducing morbidity in diabetics. Many studies have been done to elicit the risk factors and biomarkers for DME.

Imaging biomarkers such as patterns of OCT findings, those being DRT and ERM have the potential to be the indicators for assessing the severity of the disease, but significant conclusions could not be drawn due to the lack of sufficient sample. Likewise, biochemical biomarkers such as serum urea and microalbuminuria were found to be deranged in severe stages of the disease, which needs further evaluation to be concluded as indicators of disease severity

Source: Naveen et al; Clinical Ophthalmology 2022:16 3129–3134

https://doi.org/10.2147/OPTH.S377956