Comparative Doppler imaging of the ophthalmic vasculature in normal Beagles and Beagles with inherited primary open‐angle glaucoma

Abstract

The objective of this study was to compare orbital and ocular vasculature velocity, measured by Doppler imaging, in normal Beagles and Beagles with inherited primary open-angle glaucoma. Eight normal Beagles and 13 Beagles with different stages of primary open-angle glaucoma were evaluated twice with a 2-4-week period between measurements. Doppler imaging was performed with the dogs anesthetized, and the Doppler transducer applied directly on the corneal surface. The majority of the orbital vasculature (external ethmoidal artery; internal ophthalmic artery and vein; and external ophthalmic artery and vein) and ocular blood vessels (anterior ciliary artery and veins; long posterior ciliary arteries; short posterior ciliary arteries; primary retinal arteries; and the vortex veins) were identified and Doppler blood velocity parameters were determined. The glaucomatous dogs demonstrated significant differences in the Doppler velocity parameters of several orbital vessels (external ethmoidal, external ophthalmic, and internal ophthalmic arteries), and several ocular vessels (anterior ciliary, short posterior ciliary, and long posterior ciliary arteries). These differences included decreased blood velocities, and increased pulsatility and resistive indexes. The Doppler blood flow velocities of the primary retinal arteries were unchanged between the normal and glaucomatous dogs. In the glaucomatous dogs, the Doppler imaging suggests increased vascular resistance downstream in both the orbital and ocular vasculature. These blood velocity parameter changes may be primary or secondary, and may offer therapeutic opportunities to increase perfusion, prolong the retina and optic nerve head function, and maintain vision in the canine glaucomas.

Definition, Classification, and Pathophysiology of Canine Glaucoma

“…Retinal artery blood flow velocities were not different in the two groups. 105 Affected beagles investigated with the same modality during a 4-year longitudinal study showed the blood flow abnormalities to be progressive and to occur ahead of increases in IOP. 11 Whether the changes observed in dogs can be translated to humans is uncertain.…”

Eye

“…39 Administration of antiglaucoma drugs can also alter blood flow velocities and resistive indices in dogs. Specifically, decreased EDVs and increased RIs were found within their short posterior ciliary arteries (main blood supply to the canine optic disc).…”

“…3 Since then, multiple reports on the normal B-mode ultrasonographic appearance of the canine and equine eye have been published. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] Radiography, computed tomography (CT), and magnetic resonance imaging (MRI) are other diagnostic imaging modalities capable of providing detailed information about the eye, orbit, and periorbital tissues. In addition, the retrobulbar soft tissues may be imaged.…”

Progressive changes in ophthalmic blood velocities in Beagles with primary open angle glaucoma

“…CDI has been reported in normal dogs, 25,26 dogs with several ophthalmic diseases, 27 and in the Beagle with primary open angle glaucoma 28–30 . In the initial report on color Doppler imaging in the dog, the blood flow patterns were grouped into normo‐, hypo‐, hyper‐, or neovascular 27 .…”