New research assessed the use of non-invasive diagnostic technologies—such as optical coherence tomography angiography (OCT-A) and electroretinography (ERG)—for detecting early small-nerve fiber and retinal neovascular pathology in patients with diabetes.
Give me some background.
The current glucose threshold for diagnosing diabetes (7 mmol/L) has historically been based on population-based data correlating glycemic variables with retinal abnormalities (obtained via fundus examination).
However, research in recent years has detected diabetic retinopathy (DR) at 6.5 mmol/mL—indicating that such complications could develop prior to the onset of diabetes.
Now talk about the research.
A total of 75 patients (18+ years of age) with prediabetes or type 2 diabetes and meeting eligibility requirements were placed into three groups:
Group 1: Normoglycemia (n = 20)
Group 2: Prediabetes (n = 29)
Group 3: Type 2 diabetes (n = 26)
Give me some details.
All participants went through an exploratory cross-sectional analysis using the following technologies:
- Optical coherence tomography angiography (OCT-A)
- Handheld electroretinography (ERG)
- Corneal confocal microscopy (CCM)
- Electrochemical skin conductance (ESC) evaluation
How was data obtained?
In no predetermined order, a masked clinician:
- Used the RETeval device (LKC Technologies) to perform the handheld ERG in each eye.
- Obtained images from both eyes using the Heidelberg Spectralis OCT2/OCT-A (Heidelberg Engineering GmBH) following pharmacological mydriasis.
- Scanned both eyes using the Heidelberg Retinal Tomograph III Rostock Cornea Module (Heidelberg Engineering GmBH) via an established protocol.
- Measured ESC in both hands and feet of participants, directly calculated via the SUDOSCAN device (Impeto Medical).
- Performed dilated stereoscopic two-field color fundus photography to obtain images of the macula and optic disc in each eye via the Topcon TRC-50DX (Topcon Corporation).
And analyzed?
Researchers use the StataMP 16.0 (StataCorp) to assess the differences between groups via two-tailed t-tests.
Findings?
Overall, both handheld ERG and OCT-A were found to identify early retinal neurovascular dysfunction in the absence of retinopathy on fundus imaging.
According to the study authors, ERG identified a reduction in peak amplitude of retinal responses, while OCT-A demonstrated reduced parafoveal vessel density in the retina’s superficial venous plexus (SVP) and deep capillary plexus (DCP).
Tell me more.
In contrast, no differences were noted in CCM or ESC measurements between the normoglycemia and prediabetes groups.
How does this compare to prior research?
Per the authors, the data are on par with previous findings that suggested retinal neurodegeneration precedes the onset of blood-retinal barrier breakdown and retinal vasculopathy.
However, the new data seems to contrast with previous studies that identified corneal nerve loss in prediabetes (which did not occur in this instance).
What else?
The investigators stated that the results are the first report of an association between systolic blood pressure and ERG implicit time
Further, the data suggests a retinal illumination of 32-Td·s (Troland seconds) is a stronger discriminator of retinal dysfunction than 16-Td·s.
Limitations?
The relatively high waist size and body mass index (BMI) of normoglycemic controls (predominantly in males) were noted.
Significance?
Study authors concluded that the use of point-of-care devices like the ERG and OCT-A—both rapid, non-invasive, and commercially available—show promise in identifying early retinal neurovascular damage in prediabetes patients.