Understanding of the retinal circulation provided by an anomalous retinal vein.

Figure I The retinal venous pattern is shown with the superior hemiretinal vein appearing to enter into the choroid adjacent to the optic nerve (arrow). The inferior hemiretinal vein enters into the central optic disc with the arteries. vein followed the usual path and entered into the central optic disc with the artery. Colour Doppler imaging'2 was used to detect the blood velocity signals from the continuation of the inferior hemiretinal vein within the optic nerve adjacent to the central retinal artery. Spectral analysis of these signals provided a pulsatile velocity waveform which was in synchrony with the pulsations in the central retinal artery, and which was similar to the waveforms from the central retinal vein of normal controls, with a maximum velocity of 8 cm/s and a minimum velocity of 5 cm/s. The Doppler signal attributable to the superior hemiretinal vein was detected in the perineural area at the level of lamina cribrosa and continued down the side of the optic nerve to join the inferior hemiretinal vein as it exited the nerve approximately 10 mm posterior to the globe (Fig 2). The waveform in this vessel exhibited a constant peak velocity of 7 cm/s and did not manifest the normal central retinal venous pulsatile waveform.