The Relationship Between the Foveal Avascular Zone and Foveal Pit Morphology

Abstract

Purpose: : To assess the relationship between foveal pit morphology, foveal avascular zone (FAZ) and cone packing.

Methods: : Thirty - six participants (age=23±4 years) were imaged with Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, California, USA) and either the Retinal Function Imager (RFI) (Optical Imaging Ltd., Rehovat, Israel) or the adaptive optics scanning laser ophthalmoscope (AOSLO) at the University of Rochester. Depth, diameter, slope and volume of the foveal pit were extracted from the OCT thickness map. FAZ diameter and area were measured using the RFI or AOSLO images obtained. For inter-instrument comparison, two subjects were imaged using the RFI, AOSLO and fluorescein angiography (FA). Cone density was assessed using AOSLO at the University of Rochester.

Results: : The FAZ was highly variable between individuals. Area ranged from 0.047 to 1.014 mm² and average diameter ranged from 0.271 to 1.132 mm. The FAZ area was correlated with foveal pit depth (R² = 0.2652, p = 0.0005) and diameter (R² = 0.3503, p = 0.0005); deeper and broader foveal pits were associated with larger FAZ’s. The average foveal volume was 85.62 mm² (range - 24.92 to 180.30 mm²). Foveal volume and FAZ area were correlated (R²= 0.4719, p<0.0001). In two subjects, the RFI, AOSLO and FA gave equivalent estimates of FAZ area and diameter. Preliminary results show that a subject with one of the smallest FAZ and smallest foveal pit had a higher than average cone density.

Conclusions: : Our results are consistent with a developmental link between the FAZ and foveal pit formation, however, more work is needed to understand the relationship between these and other anatomical specializations of the human fovea.

Keywords: retinal development • macula/fovea • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)