Caries on the enamel surface leads to accentuation of:

A change in early enamel caries is the accentuation of the incremental lines of Retzius. This conspicuous appearance of the calcification lines is an optical phenomenon due to loss of minerals, which causes the organic structures to appear more prominent. There may also be accentuation of perikymata which are the external manifestation of striae of Retzius.  Ref: Shafer's textbook of oral pathology 7th edition page 447