Nothing to worry about.
You should have a seperate eye test ideally before the Medical so as you can be passed fit on the day.
You will have your blood pressure taken, your heart & chest listened to, a hearing test, a colour perception test, a urine sample. You usually strip to be weighed (so dress appropriately- ie: don't go commando), you will have your height measured, eye & hair color recorded together with any distinguishing scars, any tattoos are recorded & then your entire previous medical history is discussed. You also have an independent wink test to check you can close your left eye (for shootin').
If there's anything requiring further detail, the Medical Officer (MO) will write to your GP- if he/she does- ring up your Doc to majke sure they reply straight away.