यश्चक्षुषि तिष्ठञ्चक्षुषोऽन्तरो यं चक्षुर्न वेद यस्य चक्षुः शरीरं यश्चक्षुरन्तरो यमयत्येष त आत्मान्तर्याम्यमृतः ॥३,७.१८ ॥
In plain words
He who dwells in the eye, yet is within the eye, whom the eye does not know, whose body the eye is, who from within controls the eye — he is thy Self, the inner controller, the immortal.