Abstract
Purpose::
The Retinal Function Imager (RFI) is a non-invasive imaging method that provides quantitative information about blood flow (BF) velocity in the retina. It can also be used for blood oximetry, capillary bed topography, and examining the metabolic state of the retina. In this study we measured blood flow velocity in glaucoma patients and compared the results to healthy controls.
Methods::
10 eyes of 10 glaucoma patients and 7 eyes of 7 healthy volunteers were enrolled. All patients underwent testing with RFI and visual field testing (SITA) within a 6-month interval. Glaucoma was diagnosed by combining visual field and disc appearance criteria. In each patient, we scanned a 20 degrees area centered on the fovea optic nerve head (ONH).We defined secondary and tertiary branches of arteries and veins for analysis. Differences among groups were assessed by a Student’s t-test for continuous parameters and chi-squared test for categorical parameters.
Results::
There was no statistically significant difference between the average age in the glaucoma and the healthy group (69.9 ± 8.8, 64.8 ± 10.8 years respectively, p=0.1). All the glaucoma patients had high intraocular pressure; 8 had primary open angle glaucoma and 2 had exfoliation glaucoma. The mean BF velocity in arteries in the healthy group was 5.8 ± 0.9 mm/sec; significantly faster than the mean BF velocity in glaucoma patient arteries (3.9 ± 1.6 mm/sec, p=0.017). Similarly, reduced BF velocity was noted in veins of glaucoma patients (5.1 ± 1.7 mm/sec in healthy eyes, 3.2 ± 1.0 mm/sec in glaucomatous eyes, p=0.016).
Conclusions::
The RFI detected a decrease in BF velocity in retinal arteries and veins of glaucoma patients. This finding may represent a perfusion abnormality affecting the retina and optic nerve in these patients. In this case, the velocity in these vessels can be used as a measurable correlate of the vascular abnormality in glaucoma.
Keywords: imaging/image analysis: clinical • blood supply • retina