Purpose: To compare the least light density (LLD) required to elicit iris transillumination defects in donor Chinese and White irides with radial posterior iris pigment epithelium (IPE) scratches. Materials and Methods: Seven Chinese and 7 White irides were used in this study, in which 10 to 11 radial posterior IPE scratches were made under biomicroscopy. LLD for at least 3 and 6 IPE scratches was determined with a digital light meter. Histologic studies and transmission electron microscopy were carried out on each iris specimen after LLD measurement. Results: Six Chinese and all 7 White irides had qualified IPE scratch model verified by the histologic study. The average LLD required to elicit at least 3 and 6 IPE scratches in these Chinese irides were 476.5 +/- 135.7 and 855.9 +/- 290.2 Lux, respectively. In the White irides, they were 5.3 +/- 2.3 and 69.3 +/- 25.4 Lux, respectively. In histologic and transmission electron microscopy study, moderate to heavy pigmentation was seen uniformly in the Chinese irides in the IPE layer, iris stroma, and anterior surface; whereas minimal pigmentation was visualized in their White counterparts. Conclusions: LLD in IPE scratched Chinese irides were considerably higher than that of the White irides. Dense pigmentation in iris stroma and anterior surface may be the mechanism for the greater LLD in the Chinese irides and lack of iris transillumination defects in Chinese pigment dispersion syndrome patients.