Do I need to consider the size of contacts when buying them?

[El Granada]

I am a new user for contacts and I was recommended from my friend to use colored contacts recently. My eyes look bigger compared with off glasses. I really like my new look. But why do my eyes get dry and itch after wearing contacts for a while, is it because of lack of oxygen? And one day, one contact even jump out of my eyes, I was terrified, then I am guessing that the size of the contacts are too small for my eyes. Is that right? Do I need to have my eyes checked before to ensure get the correct size contacts?

[Cedarburg]

You should drop contact lenses solutions to keep your eyes from dry and don't wear contact for long time or even wear them to sleep. If you contacts keep pop out every time when you wear them, I would suggest you test your eyes to have the exact size for your eyes. If this happen after you wear them for some times, then maybe you wear your contact for a long time or check if you have infections in your eyes. All in all, it is suggested to have your eyes examined by your doctor.

[Winlock]

Every time when wearing contacts, you should have your hands washed clean and keep the contacts solution fresh! If your eyes still itch, go to your doctor!

[Claude]

I am not a contact wearer, but I guess the contact should have its size. People's eyes are different sized, some are bigger and some are smaller, how could them wear the same sized contacts?