Summary for the Clinician

››Color Doppler imaging uses ultrasound to measure ophthalmic, central retinal and short posterior ciliary arteries apostrophe blood flow velocities (cm/s) and to calculate their resistance to flow.

››Heidelberg retinal flowmeter uses a confocal scanning laser to map the blood flow in retinal capillaries and provides measurements in arbitrary units.

››Quantitative FA, using confocal scanning laser ophthalmoscopy, allows calculation of blood passage time through the retinal vasculature (s). Combined with vessel diameter measurements, this allows ocular blood flow to be calculated.

››Indocyanine green angiography provides an assessment of the choroidal filling time (s).

››Continuous recording of the change in IOP using Pascal dynamic contour tonometry provides the systolic-diastolic IOP differences known as ocular pulse amplitude. This is presumed to represent pulsatile flow within the choroid (mmHg), but has not been directly proven.

20.4  Are There Examples of Ocular

Hemodynamic Abnormalities

Found in OAG Patients?

20.4.1  Color Doppler Imaging

Rankin et al. found that OAG patients have reduced flow velocity and increased resistance to flow in the ophthalmic, central retinal, and short posterior ciliary arteries compared to controls [20]. In a 7-year prospective study, Galassi et al. demonstrated that OAG patients with progressing visual field changes have lower diastolic flow velocities and higher resistive indices in the ophthalmic artery than patients with stable visual fields [21] (Fig. 20.2).

20.4.2  Heidelberg Retinal Flowmeter

Michelson et al. found OAG patients had lower juxtapapillary retinal blood flow and neuroretinal rim area blood flow compared to age-matched healthy controls [22]. Sato et al. showed that blood flow reductions in

Fig. 20.2  Color Doppler imaging. The left picture: The color Doppler machine. The patient is seated comfortably in a half supine position. An ultrasound probe is placed on the closed eyelid and the optic nerve shadow is identified. The vessels sampled include the ophthalmic artery, central retinal artery and the nasal and temporal short posterior ciliary arteries. The

right picture: A color Doppler image of the central retinal artery and vein taken with a 7.5 MHz linear probe. The Doppler-shifted spectrum (time velocity curve) is displayed at the bottom of the image. The red and blue pixels represent blood flow movement towards and away from the transducer, respectively.