FAZ data presented here are generally consistent with previously published results. In a study using conventional FA, Bresnick et al.
13 reported a median area of 0.350 mm
2 in 20 healthy controls. In a study using a combined SLO and FA approach, Arend et al.
63 found a mean (± SD) area of 0.231 ± 0.060 mm
2 in 21 healthy controls. Using high-contrast entoptic viewing of the retinal vasculature to envisage the FAZ in 34 eyes, Bradley et al.
38 reported a mean area of 0.420 mm
2. Using contrast-enhanced FA obtained with an SLO system (Heidelberg Spectralis HRA+OCT; Heidelberg Engineering), John et al.
64 examined the FAZ in 31 healthy subjects and found a mean (± SD) area of 0.275 ± 0.074 mm
2. In a recent study in five subjects using a dual-conjugate AO fundus camera, a mean (± SD) area of 0.302 ± 0.100 mm
2 was reported.
44 Using an AOSLO device and motion contrast enhancement image processing techniques, Tam et al.
43 found a mean (± SD) area of 0.323 ± 0.107 mm
2 in 10 persons. The authors of only these most recent studies corrected their FAZ measurements for individual differences in ocular magnification because of variation in axial length. Our mean (± SD) area was 0.44 ± 0.25 mm
2, with a range of 0.05 to 1.05 mm
2, which was also corrected for ocular magnification differences. We suspect that the variation in our population is slightly higher than in previous studies given that we targeted subjects known to have foveal pits near the extremes of the normal distribution (we were explicitly interested in the relationship between foveal pit morphology and FAZ size). This fact, combined with differences in age, sex, and race of the populations studied, and the techniques used to measure FAZ make direct comparisons difficult between our study and previous studies. Nevertheless, as with other anatomic specializations of the human foveal region (e.g., cone density
65 –70 and pit morphology
28,32 –35 ), it is clear that there is substantial variation in FAZ size across persons with normal vision. Whether these retinal variations direct the variability seen in primary visual cortex remains unclear,
71 –74 though it seems logical that different distributions of retinal cells could be involved in the normal development of these structures.