Familial Retinal Arteriolar Tortuosity and Quantification of Vascular Tortuosity Using Swept-Source Optical Coherence Tomography Angiography

Abstract

Purpose : Familial retinal arteriolar tortuosity (FRAT) is a rare autosomal dominant disorder that manifests as tortuosity of the second and higher order retinal arterioles. Although FRAT has a characteristic fundus appearance, objective methods to quantify retinal vessel tortuosity are not routinely implemented when using conventional imaging techniques. We implement swept-source optical coherence tomography angiography (SS-OCTA) to quantify the tortuosity of vessel segments in patients with FRAT. We hypothesize that patients with FRAT will have higher retinal arteriole tortuosity when compared to controls.

Methods : Patients were scanned with a SS-OCTA device (Plex Elite 9000, Carl Zeiss Meditec, Dublin, CA). The flow signals from the inner limiting membrane to the outer boundary of the outer plexiform layer were isolated. An automatic tortuosity measurement program written in MATLAB was used to assess vessel tortuosity. Tortuosity was defined as the ratio between the arc length and the chord length of each vessel segment. Branch points in the vessels were detected and used to separate the vasculature into individual segments. The tortuosity was measured by calculating the arc-chord ratio, where a minimum value of 1 indicates a straight vessel and higher values correspond to increasing tortuosity. The results were compared with control eyes.

Results : Two patients (4 eyes) with a known history of FRAT and six controls (12 eyes) were included. Among right eyes, the mean tortuosity in FRAT eyes ranged from 1.1044 to 1.1438 while in controls it ranged from 1.0746 to 1.0872. Maximum tortuosity in the FRAT right eyes ranged from 2.731 to 3.997 while in control right eyes it ranged from 1.375 to 1.623. The 75^th percentile analysis showed a range of 1.122 to 1.151 in FRAT right eyes as compared to 1.082 to 1.093 in control right eyes.

Conclusions : Our results are consistent with the hypothesis that patients with FRAT have higher objective measurements of tortuosity compared to controls. Broader applications of this method may be of benefit in other retinal diseases with changes in retinal vessel configuration.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Retinal tortuosity maps of a patient with FRAT (A) and a control patient (B). En face SS-OCTA images were processed. The vasculature was segmented at its branch points and the arc-length ratio of each segment is shown using a color-coded map.