Retinal blood flow in eyes with primary open-angle glaucoma using a new Adaptive Optics Laser Doppler Velocimeter device

Purpose

To measure retinal blood flow (RBF) in the retinal veins of patients with primary open-angle glaucoma (POAG) and to compare it with healthy controls. A secondary objective was to determine any correlation between RBF and visual field (VF) loss or retinal nerve-fiber layer (RNFL) thickness.

Method

Twelve patients with POAG and 11 healthy controls were included in a prospective single-center study. Our prototype Adaptive Optics Laser Doppler Velocimeter (AO-LDV) consisted of a laser Doppler velocimeter combined with an adaptive optic fundus camera (rtx1, Imagine Eyes®) allowing measurement of blood vessel diameter and therefore, calculation of blood flow within the vessel. Blood flow in the superior temporal vein (STV) was compared with that in the inferior temporal vein (ITV). All subjects underwent eye examinations including visual field (Humphrey 24-2 SITA-standard strategy) and measurement of retinal nerve-fiber layer (RNFL) thickness using a Cirrus HD-OCT (optic disc 200 × 200 cube) protocol. Sectoral structure-function relationships were studied in the glaucoma group.

Results

The velocity in the STV was lower in the glaucoma group (6.30 ± 1.6 mm/s) compared to the control group (8.6 ± 2.8 mm/s, p = 0.07), with no significant differences in the ITV. There were no significant differences in STV or ITV diameters between the groups. We found no relationship between either STV or ITV retinal blood flow and visual field or RNFL thickness.

Conclusion

Our prototype AO-LDV allowed accurate measurement of RBF in patients with glaucoma and showed that RBF was not reduced in the early or moderate stages of glaucoma. These preliminary results should be confirmed in a larger study, especially in late-stage glaucoma.