A prospective evaluation of the Heidelberg retina flowmeter in diagnosing ischaemia following branch retinal vein occlusion: a masked, controlled comparison with fluorescein angiography

Purpose To evaluate the use of the Heidelberg retina flowmeter (HRF) in dia gnosing retinal ischaemia following macular branch retinal vein occlusion. Methods Ten patients with ischaemic macular branch retinal vein occlusion, as determined by strict fluorescein angiographic criteria, were examined wi th the HRF. Blood flow, blood volume and blood velocity characteristics fro m areas of ischaemic and non-ischaemic retina were recorded and the results between the normal and ischaemic areas of retina compared with paired t-te st analysis. Ten healthy volunteers were similarly examined and acted as a control group. Results Compared with normal retina the HRF recorded a statistically signif icant reduction in blood flow within the ischaemic retina in 7 of the 10 st udy patients. In 2 patients the HRF actually recorded a statistically signi ficant increase in blood flow in the area of ischaemic retina; there was no significant difference in the blood flow recorded in the normal and ischae mic retina in the remaining patient. HRF examination of the control group r evealed a significant difference in the blood flow between two areas of app arently normal retina in 3 of the 10 volunteers. Conclusion The HRF is not a reliable tool for diagnosing retinal ischaemia following branch retinal vein occlusion. Our results may suggest that the H RF blood flow recordings are not derived from the retinal circulation alone , but represent the cumulative blood flow through the combined circulations of the retina and choriocapillaris.