Rogers hypothesized that the two people Therapist and Client must be in Psychological Contact. Psychological contact is when both parties are fully aware of the other. There may be moments for the client when they are unaware of the other, so it is important for the the therapist to be in the relationship, by way of communicating empathy. Sometime therapists seem to be keen on eye contact possibly for this reason, but when deep internal processing is happening then eye contact may lack. Eye positions may be at the floor or another direction, and I believe that therapists should provide unconditional positive regard for this , and 'allow' it to happen without distraction - although this may conflict with the idea of a need for psychological contact. 

I will expand on the idea of Unconditional Positive Regard in another of my posts. I think think UPR is the most interesting of the core conditions, so look forwards to writing about that.