Understanding foveal development: the relationship between the avascular zone and pit morphology

Objective: To assess the relationship between the morphology of the foveal avascular zone (FAZ) and the foveal pit. Methods: Twenty-five participants were recruited (age=23±4 years) with normal vision were imaged with the Zeiss CirrusTM HD-OCT (Carl Zeiss Meditec, Dublin, California, USA) and the Retinal Functional Imager (RFI) (Optical Imaging Ltd., Rehovat, Israel). The depth, diameter, and slope of the foveal pit were calculated from the OCT data using previously described custom software.1 The diameter and area of the FAZ was measured using images obtained from the RFI, which uses motion contrast to extract blood vessel locations. Two subjects were also imaged using conventional fluorescein angiography and an adaptive optics scanning laser ophthalmoscope and the resultant FAZ metrics were compared. Results: The area of the FAZ was highly variable between individuals, ranging from 0.047 to 1.014 mm2. The FAZ area was correlated with foveal pit depth (R2 = 0.6174, p < 0.0001) and diameter (R2 = 0.2718, p = 0.0101), with deeper and broader foveal pits being associated with larger FAZ's. There were no statistical differences in area or diameter of the FAZ regardless of methods used to image. Conclusion: Our results support a developmental link between the FAZ and foveal pit formation,2 however more work is needed to understand the relationship between these and other anatomical specializations of the human fovea.