Peripapillary Blood Flow Velocity in Glaucoma Evaluated by the Retinal Functional Imager (RFI)

Abstract

Purpose: : To determine the mean peripapillary retinal blood flow (RBF) velocity in patients with various types of glaucoma, using the retinal functional imager (RFI).

Methods: : A prospective study was performed on 48 eyes of 24 subjectsreferred from an outpatient glaucoma clinic. Diagnoses included primary open angle glaucoma (POAG); glaucoma suspect (GS) and chronic angle closure glaucoma (CACG). Using the RFI and proprietary software processing, peripapillary vessels were visualized and their blood flow velocities measured. The main outcome measures were the mean RBF velocity in vessels within one disc diameter of the optic disc rim.

Results: : The mean age of subjects included was 65 ± 10.1 years. There were 14 females and 10 males. Mean peripapillary RBF velocity was 5.7±1.3 mm/s in CACG, 5.1±1.3 mm/s in POAG and 4.7±1.0 mm/s in GS. In subjects with IOP >= 16 mmHg, peripapillary RBF velocity was 5.4±1.8 mm/s; in those with IOP < 16 mmHg, arterial velocity was 4.8±1.4 mm/s. Similarly, mean peripapillary RBF velocity was 5.3±2.0 mm/s in patients whose cup disc (c/d) ratio was >= 0.6, whereas velocity was 4.9±1.7 mm/s in subjects with a mean c/d ratio <0.6.

Conclusions: : The RFI is a novel, non-invasive imaging system that allows for quantitative analysis of RBF velocity. The results of this study suggest that mean peripapillary RBF velocity is correlated with glaucoma type, c/d ratio, and IOP, the main alterable glaucoma risk factor. This might be due to a steal phenomenon in which retinal vessels experience increased flow as retinal capillary perfusion decreases. The results of this study suggest that peripapillary RBF velocity might be a useful measure of glaucoma progression risk.

Keywords: optic nerve • imaging/image analysis: clinical • blood supply