Lévitique 13:5

and the priest shall inspect him on the seventh day, and, behold, if the plague stand as it was, and have not gone on wider in the skin, the priest shall shut him up a second seven days.

to his eyes meaning, in appearance — as appearances are apprehended through the eyes. All the commentators have understood this locution to mean that the kohen who first saw the symptom must himself see no difference in its appearance.

spread from “scattered” [Nahum 3:18].

AND THE PRIEST SHALL LOOK AT HIM ON THE SEVENTH DAY, AND BEHOLD, IF THE PLAGUE STAY ‘B’EINAV.’ “This means in its original color and size.” is “in his eyes,” i.e., the eyes of the priest examining the plague. Ramban will further on stress this literal meaning of the word. This is Rashi’s language. Similarly, ‘v’eino’ (and the appearance thereof) was as the appearance of bdellium; and so also, ‘k’ein’ (like the color of) the crystal ice. as meaning “its appearance,” thus making the sense of the verse to be: and, behold, if the plague stay ‘in its appearance.’
But in the Torath Kohanim we have been taught as follows: “[From the expression here] I know only that the plague so appeared [i.e., in its original size] in his own [i.e., the priest’s] eyes. Whence do I know that the same law applies if it so appeared in the eyes of his pupil? Scripture therefore says [in Verse 37]. But if the scall stay ‘b’einav.’” Now if so, the meaning of the verse here would be: “and if the plague is at a stay in the sight of the aforementioned priest,” namely that it has remained as it was, neither having changed its place nor having spread in the skin, wheresoever the priest looks [then he shall shut him up for another seven days]. The usage [of the term a’yin (eye)] is often found in the words of the Sages. (Sages) is evidently used by Ramban here not in the strict sense of the term, as referring to the Sages of the Talmud, as I have not found this expression in Talmudic literature. It must then be a reference to the later scholars in whose writings this expression abounds. Thus: “So it appears in my eyes.” So also you find [in Scripture]: O man of G-d, I pray thee, let my life be precious ‘b’einecha’ (in thy sight], meaning, in your opinion and thought. Thus the verse here alludes to the principle that the priest in examining whether the plague has extended in the skin need only judge it as he sees it, but it is not necessary that [he base his decision] upon measuring the plague.

וראהו הכהן, it is a decree by the Torah that only a priest is qualified to determine what is ritually pure and what is ritually impure in all matters pertaining to these skin afflictions. The prophet Maleachi 2,7 echoes this concept when he says that כי שפתי כהן ישמרו דת, “that the lips (pronouncements) of the priest will preserve the Jewish religion.” The priest is also required to counsel the afflicted person to examine his lifestyle so that he himself will become the key to his rehabilitation. At the same time the Priest will add his own prayer when asking G’d to heal the afflicted. Apart from his prayer his expertise will tell him when the stage has been reached when the affliction has waned so that the count toward rehabilitation and the presentation of offerings can begin.

עמד בעיניו, “and the plague had retained the same appearance, looking the same in the eyes of the priest,” (who had examined it the last time). According to Rashi who considers the subject as being the nega, affliction, the Torah should have written עומד בעיניו, in the present tense.