Bhashya
अथ यदेतदक्षण शुक्ल भा सैव ऋक् ।अथ यन्नील पर कृष्णमादित्य इव दृक्शक्त्यधिष्ठान तत्साम ॥
In plain words
Now, the white brightness of this eye is the ṛk, and what is dark and supreme black—serving like the sun as the support of the power of vision—that is the sāman.
Close to the Sanskrit
Now, whatever is the white lustre of this eye, that indeed is ṛk. And whatever is the dark, the supreme black, like the sun being the support of the power of vision, that is sāman.