Generally it's a physical for vision, hearing, cardiovascular ....
Each class has a minimum standard for what they allow.

My concern was I'm 39 and wear contacts.
For first class you need to have distant visual acuity of 20/20 with or without corrective lenses.

My perscription is almost a year old and I didn't want to take any sinus pills before the exam so my eyes were a little bit more "blurry" than usual.

Needless to say it I was worried for nothing.

But imagine being in line and having that grating on you when you hear the Doctor tell a guy ahead of you....
"We can hold the exam for 10 days so just go out and get a new exam and lenses then come back in."

No lie that happened while I was there and it was a good thing it wasn't while I was hooked up to the EKG ( heart monitor) . lol

for more in depth data go here....

http://flightphysical.com/part67/67subb.htm