Association of changes of retinal vessels diameter with ocular blood flow in eyes with diabetic retinopathy

Abstract

We investigated morphological changes of retinal arteries to determine their association with the blood flow and systemic variables in type 2 diabetes patients. The patients included 47 non-diabetic retinopathy eyes, 36 mild or moderate nonproliferative diabetic retinopathy (M-NPDR) eyes, 22 severe NPDR (S-NPDR) eyes, 32 PDR eyes, and 24 normal eyes as controls. The mean wall to lumen ratio (WLR) measured by adaptive optics camera was significantly higher in the PDR groups than in all of the other groups (all P < 0.001). However, the external diameter of the retinal vessels was not significantly different among the groups. The mean blur rate (MBR)-vessel determined by laser speckle flowgraphy was significantly lower in the PDR group than in the other groups (P < 0.001). The WLR was correlated with MBR-vessel (r = - 0.337, P < 0.001), duration of disease (r = 0.191, P = 0.042), stage of DM (r = 0.643, P < 0.001), systolic blood pressure (r = 0.166, P < 0.037), and presence of systemic hypertension (r = 0.443, P < 0.001). Multiple regression analysis demonstrated that MBR-vessel (β = - 0.389, P < 0.001), presence of systemic hypertension (β = 0.334, P = 0.001), and LDL (β = 0.199, P = 0.045) were independent factors significantly associated with the WLR. The increased retinal vessel wall thickness led to a narrowing of lumen diameter and a decrease in the blood flow in the PDR group.

Figure 1

A circular marker was set surrounding the optic nerve head (ONH) to measure the mean blur rate (MBR) (A). The “vessel extraction’’ function of the software then identified the vessel and tissue areas on the ONH so that the MBR could be assessed separately as the vessel areas (MBR-vessel) and the tissue areas (MBR-tissue) (B). The rectangular areas (1 to 19) were set semi-automatically to the vessels around the optic nerve head concentrically and the total retinal flow index (TRFI) was calculated (C).

Figure 2

Representative images obtained with an Adaptive Optics device (images in each stages of diabetic retinopathy (DR). The images show the external diameter, the lumen diameter (LD), wall thickness, and wall to lumen ratio (WLR). Eyes in the control group (A); no diabetic retinopathy (NDR) group (B); mild or moderate non-proliferative diabetic retinopathy (M-NPDR) group (C); severe NPDR (S-NPDR) group (D); and PDR group (E) are shown. Eyes in the DR groups have higher WLR, especially in the PDR group.

Figure 3

Differences in the changes in the diameter of the retinal vessels determined by AO images among the groups. The percentage change is expressed for the four groups with diabetes, and the values are compared to that of the control group. There were no significant differences in the external diameter among the groups (A). The lumen diameter in the PDR group is significantly smaller than in the control, the NDR, and the M-NPDR groups (B). The mean wall thickness (C) and the mean wall to lumen ratio (D) in the control group are significantly lower than in the other groups. The mean wall thickness (C) and the mean wall to lumen ratio (D) in the PDR groups are significantly larger than in the other groups.

Figure 4

Representative composite color maps on the optic nerve head determined by LSFG at each stages of DR. Red color indicates a high mean blur rate (MBR), and blue color indicates a low MBR. Eyes in the control group (A); NDR group (B); M-NPDR group (C); S-NPDR group (D); and PDR group (E) are shown.

Figure 5

Differences in blood flow parameters determined by LSFG among the groups. The percentage differences are shown for four groups with diabetes and compared to the control group. The MBR of the vessels on the ONH in the PDR group is significantly lower than that in the other groups (A). There is no significant difference in the MBR-tissue among the groups (B). The total retinal flow index (TRFI) in the PDR group is significantly lower than the other groups (C).

Figure 6

Correlation of morphological variables with blood flow parameters. The lumen diameter is significantly correlated with the MBR-vessel (A) and TRFI (B). The WLR is correlated with the MBR-vessel (C) and TRFI (D).