The Size of Retinal Avascular Areas Measured with Non-invasive RFI and Flourescein Angiography

Abstract

 

Purpose:

 

We used the Retinal Function Imager (RFI, Optical Imaging, Ltd)to image the capillaries network non-invasively. We comparedthe non-invasive measurements of foveal avascular zone (FAZ)and retinal non-perfusion areas to measurements with flouresceinangiography (FA).

 

Methods:

 

Fifteen patients with retinal ischemic diseases were recruited;10 with diabetic retinopathy (DR) and 5 with vein occlusion(VO). Multiple RFI retinal image series were acquired . Followingregistration, pixel values were analyzed to locate blood cellsmotion, thus obtaining non-invasive capillary perfusion maps(nCPM) at high resolution. Patients had also FA imaging, nCPMand FA images were aligned and scale using Inkscape software.FAZ and retinal non-perfusion areas dimensions were measuredusing ImageJ (NIH, USA). Comparison between groups was doneusing student t-test.

 

Results:

 

Only the differences in FAZ area dimensions in the DR groupwere statistical significant (table, p=0.016).

 

Conclusions:

 

Using the RFI we measured larger avascular areas compared tothe measurements with FA in patients with DR. This may representunderestimation of non-perfused area due to dye leakage in FAimages. Non-invasive monitoring of the ischemic area dimensionsmay provide an important tool for early diagnosis and follow-up.  

 

 

Keywords: diabetic retinopathy • imaging/image analysis: clinical • vascular occlusion/vascular occlusive disease