Impaired retinal microcirculation in patients with Alzheimer’s disease

Figures

• 

  Fig 1. Quantitative retinal blood flow velocity map and macular blood flow. (A) The retina of a healthy subject imaged using the RFI device with a field of view of 20-degrees (4.3 × 4.3 mm2) centered on the fovea (dark area in the center) is shown. The arterioles are marked in red and overlaid with the measured blood flow velocities (mm/s); the venules and their respective velocities are marked in pink. The measured vessels cover the second, third and fourth branches of the retinal vessels. A negative value indicates blood flow away from the heart. In this case, the arteriolar flow moved towards to the fovea. A positive value indicates blood flow towards to the heart. In this case, the vessels are venules. (B) To analyze the macular blood flow, supplying the macular region including the vascular zone of the fovea, a 2.3 mm circle (blue) centered on the fovea was drawn and vessel diameters were measured in vessels at the locations (yell and green dots) crossing the circle. The diameter of the vessels which crossed the circle was determined. Blood flow of the vessel segment was calculated using the measured velocity and diameter for each arteriole (yellow dot) or venule (green dot). The…

• 

  Fig 2. Retinal blood flow, velocity and vessel diameter in AD and MCI patients compared with CN controls. (A) Total arteriolar and venular blood flow rates were calculated in the macula. Macular blood flow rates in AD group were significantly lower than MCI and CN groups (P < 0.05). In addition, the macular blood flow rates in MCI were lower than CN in both arterioles and venules (P < 0.05). (B) BFVs of all arterioles and venules in the field of view were measured. The BFV in AD group was significantly lower than in controls in the arterioles (P = 0.01) but not in venules (P > 0.05). There were no significant differences of BFVs in arterioles and venules between AD and MCI (P > 0.05). (C) Vessel diameters were measured in the vessel segments crossing a circle (diameter 2.3 mm centered on the fovea) and there were no significant differences in both arterioles and venules among the three groups. Bars = standard error.

• 

  Fig 3. Representative thickness maps, sectoral thicknesses and two dimensional retinal images of ganglion cell-inner plexiform layer. The retina was imaged using Zeiss Cirrus optical coherence tomography. AD: Alzheimer’s disease; MCI: Mild cognitive impairment; CN, cognitive normal.

• 

  Fig 4. The thickness of GCIPL. (A) The thicknesses of GCIPL in the annulus of AD and MCI groups were significantly lower than the corresponding regions in CN group (P < 0.05). (B) The thicknesses of GCIPL in the superior temporal (ST), superior (S), superior nasal (SN), inferior nasal (IN) sectors of AD and MCI groups were significantly lower than the corresponding regions in CN group (P < 0.05). In the inferior nasal (IN) and inferior (I) sectors, GCIPL thickness in AD was significantly lower than CN (P < 0.05). No significant differences of GCIPL thickness were found in the inferior temporal (IT) among groups (P < 0.05). In addition, there was no significant difference of the thickness of GCIPL in the annulus and sectors between AD and MCI (P > 0.05). Bars = standard error.

• 

  Fig 5. Relations between GCIPL thickness and macular blood flow. Annular GCIPL thickness and macular blood flow in both arterioles and venules were analyzed. There were no significant relations between GCIPL and blood flow rates in AD (A) and MCI (B). In contrast, GCIPL thickness was possibly related to blood flow rates in both arterioles and venules (C). Note both blood flow and GCIPL thickness spread out across the scales in AD and MCI groups, compared to CN group.