Morphometric age-related evaluation of small retinal vessels by scanning laser Doppler flowmetry: determination of a vessel wall index.

BACKGROUND

Measurement of the retinal vessel wall thickness may contribute to the diagnosis of microvascular diseases. We present a methodical approach to calculate these alterations and to determine age-related differences.

METHODS

One hundred fifty-three subjects without eye or internal diseases (mean age +/- SD, 47.6 +/- 14.9 years) underwent measurement of the retinal temporal superior artery and vein by scanning laser Doppler flowmetry (Heidelberg retina flowmeter). We calculated the difference between the diameter of reflectivity and the Doppler signal (Delta[VD-FD]/2) and determined a "vessel wall index" (VWI) by normalization of Delta(VD-FD)/2 for age and vessel diameter.

RESULTS

Delta(VD-FD)/2 correlated with vessel diameter (artery, r = +0.60, P < 0.001; vein, r = +0.49, P<0.001) and age (artery, r = +0.19, P = 0.02; vein, r = +0.27, P = 0.001) but not with sex, if controlled for the other variables each. The venous, but not the arterial, vessel diameter correlated with age (r = +0.18, P = 0.02), if controlled for sex. The relative statistical weight of these empirical contributions to the variation observed in Delta(VD-FD)/2 was 36.5% (P < 0.001, artery) and 21.7% (P< 0.001, vein), and that of age was 3.6% (P = 0.02, artery) and 7.3% (P = 0.001, vein). The limit value of VWI to pathologic changes (80th percentile) was 1.25 microm/y (artery) and 1.31 microm/y (vein). Delta(VD-FD)/2 normalized for vessel diameter correlated with the 10-year categories of age (artery, r = +0.196, P = 0.017; vein, r = +0.250, P = 0.002).

CONCLUSION

In a group of subjects aged 21 years to 70 years, we detected an increase of Delta(VD-FD)/2 in the retinal temporal superior artery and vein with age.