Assessing Foveal Morphology in Individuals with Fragmented Foveal Avascular Zones

Abstract

Purpose : To assess the visual acuity and foveal morphology of individuals with microvessels disrupting the foveal avascular zone (FAZ), resulting in a “fragmented” FAZ.

Methods : Of 175 individuals with no known ocular or systemic disease, nine were found to have microvessels running through the FAZ in one eye (Figure 1). In addition, one subject with amblyopia was found to have a microvessel disrupting the FAZ in her non-amblyopic left eye, and one subject with Best disease had a microvessel disrupting the FAZ in her left eye. Seven of these individuals returned for follow-up OCT imaging in both eyes and had their monocular BCVA measured. Axial length was measured using IOL master (Carl Zeiss, Meditec) to correct for ocular magnification. Foveal pit depth, pit area, and ONL thickness (using D-OCT) were measured using Cirrus (Carl Zeiss, Meditec). Foveal inner retinal area (FIRA)¹ was measured using Bioptigen (Leica Microsystems). Average avascular area and total avascular area within a 1 mm ring centered on the maximum pit depth were measured using a custom Matlab script on images acquired using the Avanti System (Optovue, Inc.).

Results : The frequency of a retinal microvessel appearing in the FAZ in our normal cohort was 5.1%. All occurrences of the aberrant vasculature were monocular. No other significant asymmetry was observed between fellow eyes including foveal pit depth, area, ONL thickness, FIRA, average avascular area, and summed avascular area (p > 0.05). All patients had at least 20/25 vision in the eye with the “fragmented” FAZ with no significant difference between eyes for visual acuity (p = 0.147, paired t-test).

Conclusions : Similar to subjects with congenital retinal macrovessels,^2,3 subjects with fragmented FAZs do not have altered visual acuity or other foveal morphology.
However further studies are needed to assess if these subjects have any capillary anomalies in the brain as reported in subjects with congenital retinal macrovessels.⁴ Biomarkers dependent on FAZ shape (i.e. area or acircularity) or detecting intraocular asymmetry will have reduced sensitivity due to the relative commonality of “fragmented” FAZs.

¹Tick PMID: 21803966
²Brown PMID:7115168
³Strampe PMID:29260109
⁴Pichi PMID:29494725

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Fig. 1. Example of a subject with a fragmented FAZ in the right eye.