As the crystalline lens ages and as cataracts develop, highly concentrated proteins in lens fiber cells undergo rearrangements leading to substantial increases in scattered light. By exploiting a relationship between scattered light and refractive index, it is shown that a rearrangement of proteins necessarily leads to increased index as well. This change in refractive index is a second-order effect and must be quite small in most cases. However, it offers a possible explanation for the increase in index and refractive power associated with the development of nuclear cataract.
Richard P. Hemenger,
"Refractive index changes in the ocular lens result from increased light scatter," Journal of Biomedical Optics 1(3), (1 July 1996). https://doi.org/10.1117/12.242695