Abstract
Purpose: :
To investigate retinal blood flow changes in optic neuropathies.
Methods: :
A Fourier-domain optical coherence tomography (FD-OCT) system with the speed of 26,000 axial scans per second and axial resolution of 5 µm in tissue was used. Flow in branch retinal veins was measured by scanning concentric circles of 3.4 and 3.75 mm diameters around the optic nerve head at a speed of 6.0 circles per second. Vessel orientation was determined from the 2 cross-sections. Flow velocity was calculated by the Doppler shift between adjacent axial scans and the vessel orientation. Volumetric flow was calculated from the cross-sectional velocity profiles in each vessel. Retinal blood flow was measured in optic neuropathy patients and compared with a normal reference group. One eye was scanned in each subject.
Results: :
Total retinal blood flow (TRBF) in 20 normal subjects was 47.6 ± 5.4 µl/min (means ± standard deviation). The range was between 40.8 to 60.2 µl/min. In 7 cases of non-arteritic ischemic optic neuropathy (NAION), TRBF was 28.2 ± 8.2 µl/min, significantly lower than normal. The range was between 11.2 to 37.2 µl/min. Three NAION patients with purely altitudinal visual field defects affecting only in the inferior field showed decreased flow in the superior retinal hemisphere, corresponding to the altitudinal loss.
Conclusions: :
We present thefirst report of Doppler OCT performed in a case series of optic neuropathy. This Doppler OCT detected a sectional decrease in retinal perfusion in NAION. The hemisphere of reduced blood flow correlated with the location of infected nerve. Doppler OCT may be useful in the assessment of optic neuropathies. Further studies will help clarify the clinical implications.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • blood supply • neuro-ophthalmology: diagnosis