Multimodal testing reveals subclinical neurovascular dysfunction in prediabetes, challenging the diagnostic threshold of diabetes.

AIM: To explore if novel non-invasive diagnostic technologies identify early small nerve fibre and retinal neurovascular pathology in prediabetes. METHODS: Participants with normoglycaemia, prediabetes or type 2 diabetes underwent an exploratory cross-sectional analysis with optical coherence tomography angiography (OCT-A), handheld electroretinography (ERG), corneal confocal microscopy (CCM) and evaluation of electrochemical skin conductance (ESC). RESULTS: Seventy-five participants with normoglycaemia (n = 20), prediabetes (n = 29) and type 2 diabetes (n = 26) were studied. Compared with normoglycaemia, mean peak ERG amplitudes of retinal responses at low (16-Td·s: 4.05 µV, 95% confidence interval [95% CI] 0.96-7.13) and high (32-Td·s: 5·20 µV, 95% CI 1.54-8.86) retinal illuminance were lower in prediabetes, as were OCT-A parafoveal vessel densities in superficial (0.051 pixels/mm2 , 95% CI 0.005-0.095) and deep (0.048 pixels/mm2 , 95% CI 0.003-0.093) retinal layers. There were no differences in CCM or ESC measurements between these two groups. Correlations between HbA1c and peak ERG amplitude at 32-Td·s (r = -0.256, p = 0.028), implicit time at 32-Td·s (r = 0.422, p < 0.001) and 16-Td·s (r = 0.327, p = 0.005), OCT parafoveal vessel density in the superficial (r = -0.238, p = 0.049) and deep (r = -0.3, p = 0.017) retinal layers, corneal nerve fibre length (CNFL) (r = -0.293, p = 0.017), and ESC-hands (r = -0.244, p = 0.035) were observed. HOMA-IR was a predictor of CNFD (ß = -0.94, 95% CI -1.66 to -0.21, p = 0.012) and CNBD (ß = -5.02, 95% CI -10.01 to -0.05, p = 0.048). CONCLUSIONS: The glucose threshold for the diagnosis of diabetes is based on emergent retinopathy on fundus examination. We show that both abnormal retinal neurovascular structure (OCT-A) and function (ERG) may precede retinopathy in prediabetes, which require confirmation in larger, adequately powered studies.

Do Black and Asian individuals wait longer for treatment? A survival analysis investigating the effect of ethnicity on time-to-clinic and time-to-treatment for diabetic eye disease.

AIMS/HYPOTHESIS: This study explored the impact of ethnicity on time-to-clinic, time-to-treatment and rates of vision loss in people referred to hospital with diabetic eye disease. METHODS: A survival analysis was performed on all referrals from an inner-city diabetic eye screening programme to a tertiary hospital eye service between 1 October 2013 and 31 December 2017. Exclusion criteria were failure to attend hospital, distance visual acuity in both eyes too low to quantify with the Early Treatment Diabetic Retinopathy Study (ETDRS) letter chart and treatment received prior to referral. Demographic and screening grade data were collected at the point of referral. Small-area statistics and census data were used to calculate indices of multiple deprivation. The main outcome measures were time taken from the date of referral for an individual to achieve the following: (1) attend the first hospital clinic appointment; (2) receive the first macular laser, intravitreal anti-vascular endothelial growth factor injection or pan-retinal photocoagulation treatment, in either eye; and (3) lose at least ten ETDRS letters of distance visual acuity, in either eye. RESULTS: Of 2062 referrals, 1676 individuals were included. Mean age (± SD) was 57.6 ± 14.7 years, with 52% male sex and 86% with type 2 diabetes. The ethnicity profile was 52% Black, 30% White, 10% Asian and 9% mixed/other, with similar disease severity at the time of referral. Time-to-clinic was significantly longer for Asian people than for Black people (p = 0.03) or White people (p = 0.001). Time-to-treatment was significantly longer for Black people than for White people (p = 0.02). Social deprivation did not significantly influence time-to-treatment. There were no significant differences in the rates of vision loss between ethnic groups. CONCLUSIONS/INTERPRETATION: Black people wait longer for hospital eye treatment compared with their White counterparts. The reasons for this delay in treatment warrant further investigation.