IF you are not sure about your eyes, I suggest that you get your prescription from your optician and fax it to the Safety Regulation Group (SRG) at the CAA in Gatwick (fax number is on their web site I imagine)
They will then say whether is is worth while going for the medical. They are very nice people, and they always do their best. You need to know the sooner the better. It will either take a weight of your shoulders or cause dissapointment now but you wil get over it sooner than you think. Dont put it off. Better to try and fail than to never try at all.