It is very unlikely that you have done yourself any lasting damage with the dosing you describe, provided that firstly this was an isolated incident and not part of a pattern of overuse, and secondly that the MDMA was indeed MDMA and not something else more harmful. If anyone else you were with took MDMA from the same source, have they experienced similar symptoms? Have you taken MDMA before, and if so was this experience significantly different to any previous experiences?
If the answer to both those questions is "no", you can be reasonably (although not completely) sure that your symptoms are not the result of taking a substance other than what you thought you were taking.
In any case the best way to quickly rule out any lasting visual changes is to go visit an opticians, depending how comfortable you are with being honest or what part of the world you live in you can mention or not menton drugs as you see fit, but just explain your other symptoms and get them to test your eyes. If they don't find anything measurable (as I suspect will be the case) you can be reassured that you are most likely OK and any persistent distortions are likely psychological in origin and thus should clear up with time.
As for the balance issues, again, you need to ascertain if this is merely a feeling or something actually measurable. Do you play any sports? If so, have you noticed a marked deterioration in your performance? If you do not play any sports, start! Exercise does wonders for psychosomatic feelings of weakness, and just practicing activities requiring physical coordination should cause any balance issues to quickly resolve. If you still have noticeable balance issues even after making an effort to improve them, then it might be time to go see a doctor. However the doses you described are not dangerous amounts and therefore I strongly suspect that this will not be necessary.
