ASSESSMENT OF RETINAL VASCULITIS USING THE RETINAL FUNCTION IMAGER (RFI)

Abstract

 

Purpose

 

Recent advances on optical imaging techniques enable imaging the retinal microvasculature at the capillary level. Herein we present the feasibility and applicability in diagnostic imaging of the retinal blood flow (BF) velocity and in assessing high-resolution, non-invasive capillary perfusion maps (nCPMs) in patients with retinal vasculitis using a commercially available Retinal Function Imager (RFI, Optical Imaging Ltd, Rehovot, Israel).

 

Methods

 

The RFI is a fundus camera-based device with an attachment of a specific camera that captures reflectance changes as a function of time under stroboscopic illumination. This device was originally designed to measure the BF velocity directly and noninvasively (without using any contrast agent) in secondary and tertiary retinal vessels while using the hemoglobin in the red blood cells as an intrinsic motion-contrast agent. In a pilot study we measured the retinal blood flow velocity (Fig. 1) and generated the nCPMs (Fig. 2) with the RFI in 7 patients (m:f=2:5) with a mean age of 51±11 years. Five of these patients suffered from Birdshot Chorioretinopathy and two patients had a retinal vasculitis of unknown origin. We compared these data with a healthy control group (n=32 patients; published data by Burgansky-Eliash et al. in Retina 2010;30(5):765-773).

 

Results

 

In the control group the blood flow velocity in the arteries was 4.1±0.9 mm/s and in the retinal veins 2.9±1.0 mm/s. Comparing these data with the retinal BF velocities of the study group, we achieved significant differences. The vasculitis patients disclosed an arterial blood flow velocity of 2.5 ±1.6mm/s (p<0.0001) and a venous BF velocity of 1.8±1.0 mm/s (p<0.0001). The microvasculature anatomy revealed by the nCPMs appeared unevenly distributed, and lower number of blood vessels along with lower degree of complexity of their branching patterns were evident when compared with a normal healthy eye.

 

Conclusions

 

With the RFI we could show for the first time, that in patients with retinal vasculitis the arterial as well as the venous blood flow velocity are significantly reduced. Thus, imaging the retinal vasculature with the RFI could offer both - a diagnostic and quantifying tool in retinal vasculitis patients and, in addition, a facility for assessing the effectiveness of treatment.

 

 

 

Keywords: 550 imaging/image analysis: clinical • 746 uveitis-clinical/animal model