The fovea is often assumed to be at the center of the foveal avascular zone (FAZ), which can be demarcated using fluorescein angiography (FA), high contrast imaging with moderate to high magnification and short wavelengths, or entoptic methods (Bradley et al.,
1998; Martin & Roorda,
2005; Zeffren, Applegate, Bradley, & van Heuven,
1990). There is large variability in the size of the FAZ, even in normal individuals (Bird & Weale,
1974). The size of the FAZ increases in patients with retinal vascular pathology (Applegate, Bradley, van Heuven, Lee, & Garcia,
1997; Arend et al.,
1991; Conrath, Giorgi, Raccah, & Ridings,
2005; Hilmantel et al.,
1999; Mansour,
1990; Yap, Gilchrist, & Weatherill,
1987), and with capillary dropout, there can be the appearance of several avascular regions. Similarly, there is inter-individual variability in the extent and distribution of the vessel arcade pattern, making precise foveal localization difficult (Bradley et al.,
1998; Zeffren et al.,
1990). Due to the invasive nature and potential risks of FA (Kwan, Barry, McAllister, & Constable,
2006; Yannuzzi et al.,
1986), it is not used to locate the fovea in the absence of retinal disease. Non-invasive, entoptic methods use short wavelength light to enable subjects to visualize the FAZ by the absence of leukocyte activity in the retinal circulation (Bradley, Applegate, Zeffren, & van Heuven,
1992; Riva & Petrig,
1980; Yap et al.,
1987) but are subjective and require a patient to have sufficient visual function to detect small blood vessels or small, moving leukocytes. Similarly, there is inter-individual variability in the extent and distribution of the vessel arcade pattern, making precise foveal localization difficult (Bradley et al.,
1998). Furthermore, FA and entoptic methods show an increase in the FAZ individuals with retinal vascular pathology (Applegate et al.,
1997; Arend et al.,
1991; Conrath et al.,
2005; Hilmantel et al.,
1999; Mansour,
1990; Yap et al.,
1987), and with capillary dropout, there can be the appearance of several avascular regions.