In the Evans-Fung and Yurkin models, the parametric coefficients are completely determined once , , , and are known and vice versa. However, it should be mentioned that the parametric equations given by Eqs. (2) and (3) could not be of the expected biconcave shape. To illustrate this feature, the values of , , and are fixed at the averaged values reported in Evans and Fung with the parameter varying in the range between 0.05 and 0.95. We found that the shape given by Eq. (1) is not a biconcave shape when is smaller than approximately 0.6 (i.e., ) or larger than 0.89 (i.e., ), as evident in the three top panels of Fig. 2, which show typical geometries determined in Eq. (1). The results indicate that the parametric model based on Eq. (1) has a limited range of the parameter . Because is rarely reported in experiments, , , and cannot be determined only based on , , and . The extra morphological parameters can be specified through the determination of the particle volume, the particle surface area, or other geometric parameters. Similarly, we plotted the three typical geometries shown in the lower panels of Fig. 2 according to the Yurkin model. When is smaller than , the resultant geometry is not the expected shape, and the dimple thickness is larger than the given value. The reason for failing to obtain the expected geometry is due to the existence of different branches of geometry. Figure 3 shows the variation of the particle volume, the surface area, and as a function of . The Yurkin model has a larger range of deformation. The volume and index predicted from the Yurkin model are always larger than those of the Evans-Fung model. The surface area of the Yurkin model is smaller than that of the Evans-Fung model when is less than 0.87.