Abstract
Purpose: :
To evaluate the relationship between retinal thickness and retinal hemodynamic abnormalities in patients with type 2 diabetes and non-proliferative diabetic retinopathy (NPDR).
Methods: :
A total of 36 participants were recruited for the study; 10 non-diabetic control subjects (NC) (4 M: 6F, mean age of 54.3 ± 13 yrs), 14 mild-to-moderate NPDR subjects (M-NPDR) (4M: 10F, 64 ± 9 yrs), and 12 moderate-to-severe NPDR subjects (S-NPDR) (6M: 6F, 62 ± 11yrs). Six retinal images were acquired non-invasively using the Canon Laser Blood Flowmeter to assess arteriolar diameter, blood velocity, max-to-min velocity ratio (a parameter reflecting vascular compliance) and flow. Retinal thickness (RT) in nine ETDRS subfields was measured using the Spectralis OCT. The nine ETDRS subfields included; central subfield (CSF); superior inner macula (SIM); superior outer macula; nasal inner macula (NIM); nasal outer macula; inferior inner macula (IIM); inferior outer macula (IOM); temporal inner macula (TIM); temporal outer macula (TOM).
Results: :
No significant differences were found in terms of retinal arteriolar diameter, blood velocity or flow between groups. However, max:min velocity ratio was significantly elevated in the S-NDPR group (p=0.031). There were no significant differences between the 3 groups in RT in the nine ETDRS subfields. Mean CSF values for NCs was 278.4 ± 22.8 vs. 261.0 ± 23.7 and 270.7 ± 17.4 μm in the M-NDPR and S-NDPR groups, respectively (p=0.159). There was a tendency for the inner macular RT to be lower in M-NDPR compared to the NCs, including; SIM (p=0.297), NIM (p=0.151), IIM (p=0.070) and TIM (p=0.269). In M-NDPR, retinal blood velocity positively correlated with RT (r> 0.56, p<0.040) in 7 of the 9 ETDRS subfields but not in the CSF and IOM fields. Also in M-NDPR, log max:min velocity ratio was negatively correlated with 8 of the 9 ETDRS subfields (r> 0.55, p< 0.015) but not in the CSF field.
Conclusions: :
Our results showed that a lower RT in the macular subfields (other than the CSF field) is associated with lower arteriolar blood velocity and increased vessel rigidity in patients with mild-to-moderate NPDR.
Keywords: diabetic retinopathy • imaging/image analysis: clinical • blood supply