Quantitative changes in perifoveal capillary networks in patients with vascular comorbidities

To determine if patients with cardiovascular comorbidities but no clinically detectable retinal disease demonstrate quantitative alterations to perifoveal capillary networks.

Comparisons were made between 10 eyes from patients with vascular comorbidities and 17 control eyes. All eyes were absent of clinically evident ocular disease. Microcannulation techniques were used to label the retinal microvasculature. Retinae were flat mounted, and the peripapillary region 2 mm nasal to the fovea was imaged using confocal laser scanning microscopy. Two- and three-dimensional image reconstructions were used to perform quantitative measurements of individual capillary networks within the perifovea. Parameters measured included capillary diameter, capillary loop area, capillary loop length, capillary density, and capillary surface area.

Capillary diameter was increased in the retinal ganglion cell and superficial inner plexiform layer capillary network in patients with vascular comorbidities. Capillary loop area and capillary loop length were reduced in all capillary networks in patients with vascular comorbidities except the deep capillary network of the inner nuclear layer. Capillary density was reduced in the nerve fiber layer capillary network in patients with vascular comorbidities. There was no difference in the relative occupied capillary surface area between control and diseased eyes.

The results in this study suggest that the quantitative characteristics of perifoveal capillary networks are nonuniformly altered in patients with vascular comorbidities, before the onset of clinically identifiable eye diseases. These findings may be important for understanding pathophysiological mechanisms involved in retinal vascular diseases.