Comparative Analysis of ARIA and IVAN Vessel Caliber Measuring Software Applications

Abstract

 

Purpose:

 

The relationship between changes in retinal vascular morphology and systemic disease is well recognized. There are several software applications available which map and measure the caliber of the retinal vessels. The aim of this study is to compare the values generated by Automated Retinal Image Analyser (ARIA), custom-written vessel segmentation and analysis software (Peter Bankhead, Queen’s University Belfast) with the IVAN software which has been used in many epidemiological studies (Nicola J. Ferrier, University of Wisconsin, Madison).

 

Methods:

 

The images selected for comparison were taken from the Irish Nuns Eye Study (INES) cohort, captured on the Nidek AFC210 through dilated pupils. A calibration figure was calculated from 26 eyes selected at random. The distance in pixels from centre macula to centre optic disc (CM-CD) was measured in Adobe Photoshop and recorded in a spreadsheet. Using the accepted distance of 4500µm and the refraction values for each eye, the CM-CD value was adjusted using the Spherical Equivalent Refraction (SER) for each eye. The resulting mean value for calibration was 1px=6µm. A further 20 eyes (one eye from each individual) were selected for the comparative caliber measurements. These were processed through both applications. One major artery and vein in each quadrant were measured. To avoid confusion all smaller retinal vessels were deleted. The values (label, no of diameters and mean diameter) for the 8 chosen vessels from each image from both platforms were exported to a spreadsheet. Averages for each quadrant were calculated for arteries and veins and the percentage difference calculated.

 

Results:

 

Results show that the ARIA software returned larger measurements for all the vessels assessed. However the artery to vein (A/V) ratio was virtually identical in both applications. The average values for the vessels and A/V ratios are shown in µm in the table below.

 

Conclusions:

 

Both applications are straightforward to use and produce similar A/V ratios. However, in this small sample the ARIA software produces larger values for each vessel. This is not unexpected as both pieces of software use different metrics for defining the vessel edge. From a practical view point there are also some important differences between the two platforms.  

 

Keywords: imaging/image analysis: clinical • retina • image processing