I think I'm starting to understand a little better.

The right eye represents rules, law, duty, 'correct' behaviour; an [occultist] would likely call it obedience and submission . The left represents self-interest, passion, independence; the same [occultist] would likely call it freedom to 'do as thou wouldst'.

It's not about good and evil. Rules and duty are not always positive (it depends which rules you're following and the effects that your actions have), and the self is not always negative (even selfishness can be positive, depending on the circumstances). A devout Satanist priest probably walks the right-handed path (Satan's rules), while a Gnostic hermit who never hurt anyone in their life would probably be on the left-handed.

A healthy person has traits of both the right and left eyes, with the two in approximate balance. To have one to the exclusion of the other is hurtful and negative; either to the self (left missing), the greater whole (right missing), or both (ultimately, hurting oneself hurts the group, and hurting the group hurts oneself).

Harmony and balance in all things. Yin and yang, etc.

I still don't understand what closed (or completely missing) eyes represent yet, but I'm working on it.