my wife, who is totally comfortable diving, has the same type of issue. for her it seems to be a psychological thing when she enters the water from a boat and cannot see the bottom. we find that if we get in the water before other divers (so we are not feeling rushed), descend down the line slowly (feet first) while maintaining eye contact, we usually reach the bottom with no issues. it's like, "oh, we're here already ??"
i have also seen others that become very disoriented because there is no point of reference and they get very anxious. the suggestions made above about having divers below to focus on should help if that is part of the issue.
only other advise i would give is try not to think about it before the dive. don't focus on the fact that viz is short and you cannot see the bottom. try to keep breathing under control. stay relaxed. and make sure weighting is proper (not too heavy) and buoyancy is good. you always want to feel in control of your descent and not that you are plummeting into the abyss. haha good luck keep trying new techniques. you will find what works for you !!