Abstract
Purpose :
Carotid-cavernous fistulas (CCF) are often difficult to diagnose without invasive angiography, and can lead to ocular morbidity.
We tested the hypothesis that high temporal resolution blood flow imaging would allow the discovery of dynamic retinal and optic nerve flow changes characteristic of a carotid cavernous fistula in a case-control study.
Methods :
Consecutive patients with carotid-cavernous fistulas underwent measurement of ocular blood flow using Laser Speckle Flowgraphy at baseline and after spontaneous or endovascular closure of the fistula when possible. Intravascular flow velocities were measured with Relative Volume Flow (RFV), plotted over an average cardiac cycle. Waveform characteristics including phase and amplitude were calculated for companion arteriole-venule pairs. Outcomes included the difference in phase between the arteriolar and venular flow, as well as the relative pulsatility of the arterioles and venules.
The results in the CCF cohort were compared to normal subjects (n=32) and patients with conditions other than arteriovenous fistulas that share common features such as elevated intraocular pressure or venous stasis (n=40).
Results :
Venule-arteriole RFV phase delay was significantly greater in eyes with CCF (10.7% ± 2.2) compared to unaffected fellow eyes (1.8% ± 0.2, p=0.05) or control eyes of normal subjects (2.7% ± 0.3, p=0.02). This phase delay was associated with a paradoxical decrease in venule RFV during systole, and neither was present in patients with papilledema, NAION, glaucoma, or retinal vein occlusion. The delay and the systolic depression of venular blood flow velocity disappeared after fistula thrombosis. The venule:arteriole waveform amplitude ratio in CCF cases was increased compared to fellow eyes and normal controls (1.71±0.3 vs 0.54±0.03 vs 0.59±0.02, p<0.00001). This amplitude change was seen to a lesser extent in papilledema cases.
Conclusions :
Laser Speckle Flowgraphy reveals dynamic retinal vascular changes in eyes affect by a carotid-cavernous fistula not present in healthy controls or patients with other eye conditions, which reverse with treatment. These findings could potentially be used for noninvasive diagnosis at the point of care.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.