Quantitative Angiography as a Diagnostic Tool for Objective Control of Rheopheretic Treatment in Age Related Macular Degeneration (AMD)

Abstract

Purpose: : Studies have shown that an optimization of the haemodynamic properties of the blood by therapeutical apheresis has a positive effect on patients with the dry form of AMD [1, 2]. This effect is attributed to a renormalisation of the diminished perfusion in the submacular coroidal circulation [2, 3]. Detailed investigations of the perfusion and its changes under treatment are still missing. At this, a major problem is the quantification of perfusion diminishments and their changes whereas conventional angiography allows qualitative investigations only. To this aim we investigated whether quantitative angiography can be used to show whether rheopheresis has a measurable impact on choroidal circulation.

Methods: : Patients undergoing Rheopheresis for dry AMD were included and measurements correlated to a healthy age matched volunteer. The procedure of quantitative fluorescence angiography comprised the following steps: 1. Angiography sequence as raw data 2. Eye movement correction 3. Appearance curve of the fluorescent agent for each pixel 4. Mathematical curve fit for each pixel 5. Characteristic parameter for each pixel (threshold related appearance time) 6. Topographic representation of the quantified perfusion

Results: : Two patients with dry AMD undergoing rheopherisis were included. Before the Rheopheresis we observed a threshold related appearance time of 35 and 50 arbitrary units and after Rheopheresis 25 and 40 arbitrary units. These data were compared to a healthy volunteer with a threshold related appearance time of 11 arbitrary units.

Conclusions: : Quantitative angiography could be a useful method to detect and quantify discrete diminishments of macular perfusion which might be of value in therapies attempting to improve it.

Keywords: age-related macular degeneration • imaging/image analysis: clinical • image processing