Hi. I'm online and happy to answer your question today.
From what you have posted I do not believe that the treatment of the AK with liquid nitrogen caused any damage to your eyes at all.
If, indeed, the liquid nitrogen got into your eye the only damage it would cause would be damage secondary to freezing. If this were to have happened you would have known it at the time as it would have affected your vision and hurt.
Remember, 70% of the air you breath is nitrogen...as such the nitrogen gas is not dangerous in and of itself.
I doubt that your eyes were frostbitten without you being aware of it.
Is there anything else you would like to discuss at this point or have all your questions been answered to your satisfaction?
I hope this information was helpful for you. But I do work for tips so I want to make sure you are happy with me before rating me. If you have another question on this or a related issue feel free to fire away. And please let me know if the rating system gives you any troubles. Thanks in advance, Dr. Rick MD FACS