A recent study proposed a method to predict the progression of retinopathy by studying different phenotypes of type 2 diabetes.
According to recent estimates, the prevalence of diabetic retinopathy (DR), which to date is one of the leading causes of blindness worldwide, could double in the next decade.
Considering that more than 90% of cases of vision loss are preventable, accurate staging and classification of DR are crucial to guide the clinician's decisions on the most appropriate treatment and determine a favourable prognosis.
To date, the gold standard for staging DR is the ETDRS (Early Treatment Diabetic Retinopathy Study), the application of which, however, remains limited outside the research context.
In this new study, researchers followed a group of patients with type 2 diabetes and mild non-proliferative diabetic retinopathy (NPDR) over a five-year follow-up and found individual variations in the progression of RD and the development of sight-threatening complications.
Using non-invasive imaging methodologies (colour fundus photography and optical coherence tomography), three different phenotypes of NPDR were identified, based on microaneurysm turnover (MAT) and central retinal thickness (CRT), which are associated with a different risk of developing sight-threatening complications.
The three phenotypes identified were named A, B and C: phenotype A is characterised by low MAT (<6) and normal CRT, phenotype B has low MAT (< 6) and increased CRT, phenotype C has higher MAT (≥ 6) with or without increased CRT.
These different retinopathy phenotypes in type 2 diabetes show a different 5-year risk for the development of diabetic macular oedema and proliferating diabetic retinopathy (PDR).
In fact, the study showed that eyes with phenotype C are at higher risk of developing sight-threatening complications and that this is the only phenotype associated with PDR.
In contrast, phenotype A identifies eyes that have a very low risk of developing sight-threatening complications.
The study shows, therefore, that the C phenotype is a good predictor of worsening retinopathy.
Furthermore, the study shows that automated MAT analysis correlates well with changes in ETDRS severity levels, validating its use as an easy-to-use biomarker for DR progression. Increased MAT values in phenotype C, independent of CRT values, appear to identify eyes that will develop vision-threatening complications such as diabetic macular oedema and proliferative diabetic retinopathy.
Thus, patients who can be identified with these parameters are those who need to be followed more closely by clinicians.
Phenotype C was mainly identified in eyes with baseline ETDRS level 35, suggesting that ETDRS level 35 may be the turning point in the progression of diabetic retinopathy. Eyes with ETDRS level 35 apparently reach a state of microvascular damage that creates the conditions for the identification of phenotype C. In this particular study, approximately 44% of the eyes classified as ETDRS level 35 at baseline were classified as phenotype C. Among these, 23% experienced a worsening of ETDRS grade and retinopathy during the 5-year follow-up period, which was only seen in 2% of patients with phenotype A or B.
A correlation was also observed between capillary closure, as identified by the decrease in vascular density, and the severity of retinopathy progression, which could therefore represent a potential early marker of DR severity progression.
In the cohort, a 70% of patients with phenotype A and B were identified as having a very low risk of worsening. This observation is particularly relevant for appropriate eye care planning for the large number of patients with type 2 diabetes and mild retinopathy.
Finally, a strength of the study is that the imaging techniques used, i.e. colour fundus photography and optical coherence tomography, for the assessment of the biomarkers considered, are easy to perform and can be repeated without major inconvenience to the patient or clinical staff.
The study confirms the potential of the analysed variables, MAT and CRT, for assessing the progression of DR severity, opening new avenues for better management strategies of non-proliferating diabetic retinopathy and the early identification of patients at risk of retinopathy progression.
Bibliography:
Dr. Carmelo Chines
Direttore responsabile
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