Figure 5. Iris surface pigmentation. Pigment accumulation on the anterior surface of the iris often appears as concentric rings within the iris furrows. More diffuse pigmentation can cause a diffuse darkening of iris color, which is more apparent in lightly pigmented irides because of the degree of color change. Asymmetry of pigment liberation may result in iris heterochromia, with the darker iris being the more affected side.
If you do more research you'll find that there are different reasons/sorts of PGS. What it appears this woman has represents just one sort. Of course you're going to find pictures of the other sorts.
(no subject)
Pigment accumulation on the anterior surface of the iris often appears as concentric rings within the iris furrows. More diffuse pigmentation can cause a diffuse darkening of iris color, which is more apparent in lightly pigmented irides because of the degree of color change. Asymmetry of pigment liberation may result in iris heterochromia, with the darker iris being the more affected side.
If you do more research you'll find that there are different reasons/sorts of PGS. What it appears this woman has represents just one sort. Of course you're going to find pictures of the other sorts.