TT #129 · Parshas Tazria · Aliyah 2 · Passuk 12
English: If the eruption spreads out in the skin, so that the eruption covers all the skin of the affected person from head to foot, as far as the priest can see,
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:12
Torah Temimah cites Sifra (Toras Kohanim) for the requirement that the examining kohen be able to see the lesion.
Sifra — Vayikra 13, Midrash Sefer
English: “For every appearance of the eyes” excludes a blind priest from inspecting the lesions.
Textual derivation
The examining kohen must be able to see the lesion; a blind kohen cannot perform this visual examination.