The Sun is like the eye of the Supreme Lord.
The sun-god is considered to be the chief of the demigods. He is also considered to be the demigod who watches the northern side of the universe. He gives help for understanding the Vedas. As confirmed in Brahma-samhita (5.52):
yac-caksur esa savita sakala-grahanam raja samasta-sura-murtir asesa-tejah
yasyajnaya bhramati sambhrta-kala-cakro govindam adi-purusam tam aham bhajami
“The sun, full of infinite effulgence, is the king of all the planets and the image of the good soul. The sun is like the eye of the Supreme Lord. I adore the primeval Lord Govinda, in pursuance of whose order the sun performs his journey, mounting the wheel of time.” The sun is actually the eye of the Lord. In the Vedic mantras it is said that unless the Supreme Personality of Godhead sees, no one can see. Unless there is sunlight, no living entity on any planet can see. Therefore the sun is considered to be the eye of the Supreme Lord. That is confirmed here by the words yac-caksur asit and in the Brahma-samhita by the words yac-caksur esa savita. The word savita means the sun-god.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Eighth Canto, Chapter 5 – Text 36
