1. Noninvasive polarized light microscopy quantitatively distinguishes the multilaminar structure of the zona pellucida of living human eggs and embryos 
Cory Pelletier, B.A., David L Keefe, M.D., James R Trimarchi, Ph.D. 
Fertility and Sterility 
Volume 81, Pages (March 2004)
DOI: /j.fertnstert

2. FIGURE 1
The multilaminar structure of the zona pellucida can be quantified with PolScope imaging. Human egg, imaged with differential interference contrast optics (A) and with the PolScope (B). (C) Cleavage-stage (day 3) embryo imaged with the PolScope. Distinct zona layers can be imaged with the PolScope. (D) Thickness and retardance of the zona and each of its layers were measured with spindle view in eight octants around the egg and embryo. (E) Contributions of individual zona layers to total zona thickness of eggs and cleavage stage embryos. Scale bars = 20 μm.
Pelletier. PolScope views laminar zona.Fertil Steril 2004.
Fertility and Sterility  , DOI: ( /j.fertnstert )

3. FIGURE 2
Embryo zona are thicker, primarily owing to thinning of layer 3. Comparisons of overall zona pellucida thickness (A), individual layer thickness (B), and individual layer retardance (C). Small dots are averages of eight measurements from individual eggs and embryos; large dots and bars represent averages and SDs.
Pelletier. PolScope views laminar zona.Fertil Steril 2004.
Fertility and Sterility  , DOI: ( /j.fertnstert )

4. FIGURE 3
Zona retardance increases proportionally with increasing layer thickness. A relationship exists between zona layer 1 thickness and layer 1 retardance for immature eggs, mature eggs, and embryos. Inset demonstrates that this positive correlation holds for a cohort of embryos from a single patient.
Pelletier. PolScope views laminar zona.Fertil Steril 2004.
Fertility and Sterility  , DOI: ( /j.fertnstert )

5. FIGURE 4
Zona layers exhibit variation within a cohort of eggs or embryos, between patients, and around individual eggs. Comparisons of zona pellucida layer thickness (A), variance in layer thickness (B), layer retardance (C), and variance in layer retardance (D) from cohorts of embryos grouped by patient. The zona of eggs and embryos from the same patient vary considerably (A and C). The thickness and retardance of the zona varies around individual eggs and embryos (B and D). Small dots are averages of eight measurements from individual eggs and embryos; large dots and bars represent averages and SDs.
Pelletier. PolScope views laminar zona.Fertil Steril 2004.
Fertility and Sterility  , DOI: ( /j.fertnstert )