It is a Mental Perception
The Hebrew word for "eye" (עַ֫יִן) can carry a figurative meaning "of mental and spiritual faculties."
Likewise, the Hebrew verb "see" (רָאָה) can carry a figurative meaning of either mental perception or recognition.
Now in Job 42:1-6, Job had just completed enduring a thorough, direct, verbal chastening and educating by God (speaking from the whirlwind, Job 38:1, 40:6) about God's nature (focusing a lot on His power and might) versus Job's own nature (who is he to question God?). This occurs, with just a few short breaks, from Job 38:1-41:34.
Job declares he has been educated in things he "did not know" through this, and indeed still lacks a full understanding (42:2-3). But he has listened ("I have heard of You by the hearing of the ear," 42:5a) and so "now my eye sees You" (42:5b) is reflecting on his knowledge gained by the experience of God's chastening words (and his whole experience in being tormented by Satan). And because of this knowledge, Job now "abhors" himself and repents of his prior, ignorant statements that reflected poorly on God's character and nature (v.6).
Now it is true that "hearing" and "ears" can be figurative to mean understanding also (some examples: Dt 29:4, Ps 115:6), but here the passage appears to be using literal in the first, and figurative for the second, based on the facts that:
- It is very explicitly stated "I have heard of You by the hearing of the ear." So to me, the "of You" either means literally the source (i.e. God speaking, equivalent to "heard from You") or literally the content (i.e. about God). Either fits the context, but both refer to the words spoken.
- The following contrast "but now" implies the "seeing" is a different experience than the hearing (so they cannot both be referring figuratively to understanding). Though obviously the eye seeing could be literal still in this contrast, but the other points I made I think argue against that.
- The context has God directly speaking to Job (so he indeed "had heard" from God just then).
So there is no need to try to view this as being an actual "physical" seeing of God. The context points to a mental and spiritual awareness that has come to Job through the whole experience, and this is the most likely meaning, in context, of what "now my eye sees You" refers to. He is expanding on his actually "hearing" having brought an "understanding" he did not previously have.
1 Francis Brown, Samuel Rolles Driver, and Charles Augustus Briggs, Enhanced Brown-Driver-Briggs Hebrew and English Lexicon (Oxford: Clarendon Press, 1977), s.v. עַ֫יִן, no. 3. Some examples are Adam and Eve's eyes opened to good and evil (Gen 3:5, 7), eyes shut to understanding (Isa 44:18), and others, and even in Job, "eyes" fail to perceive the place where wisdom and understanding come from (Job 28:20-21).
2 Ibid., s.v. רָאָה, no. 3, 5, 7. Some examples, God "sees" wickedness in men (Job 11:11), God "saw" that His creation was "good" (Gen 1:10, 12), the writer of Ecclesiastes tells his heart to "look" at the greatness attained (Ecc. 1:16).